Saturday, July 4, 2009

LCD + Touchscreen Interfacing

First - Sorry for the lack of posts here. I was down in the hospital with acute appendicitis (had to remove the appendix and a small part of the large intestine where it attached due to extreme infection!). Needless to say that was not fun!!!

Now - One of the items I am looking to use with the gumstix computer is a LCD display with touchscreen capability. Gumstix sells a Samsung 4.3 inch (diagonal) LCD display (LTE430WQ-FOC) for the gumstix computers. The description and specifications of the LCD display are:

LTE430WQ-F0C is a TMR(Transmissive with Micro Reflective) type color active matrix TFT (Thin Film Transistor) liquid crystal display (LCD) that uses amorphous silicon TFT as a switching devices. This model is composed of a TFT-LCD module, a driver circuit and a back-light unit and a Touch Screen Panel(TSP). The resolution is 480 X 272 X RGB dots and can display up to 16.7M colors.

- Transmissive with Micro Reflective type and back-light with 10 LEDs are available.
- Visible in outdoor & back-light off condition with reflectivity.
- Using the Touch Screen Panel (Film to Film-Glass type).
- VA(Normally black) mode.
- 24-bit RGB Interface (8-bits per color)
- DE(Data Enable) & SYNC mode - DE, Vsync, Hsync, DOTCLK

- Display terminals for PMP(Portable Multimedia Player) , Portable CNS(P-CNS)
application products.
- Display terminals for AV application products

In order to use the LCD display with the computer you also need the LCD interface board which is also sold by Gumstix. The Palo-43 board contains all the LCD interfacing circuits, the power supply for the LCD and Gumstix Com board and voltage level shifting hardware needed to use the Samsung LCD display with the Gumstix COM computers.

Not only are the basic interfaces on the board to drive the LCD display there are also other interfaces for audio in and out, USB OTG connectivity, USB console connectivity and interface connections that allow access to some of the other interfaces available on the Gumstix COM computers (I2C, SPI, A/D input PWM output and so on). The description and specifications of the LCD display are:

  • Signals available on 0.100" through-holes at 1.8V logic
  • ---Two (2) two-wire serial ports
  • ---One 1-wire port
  • ---6 PWM lines
  • ---I2C port
  • ---SPI bus
  • 6 A/D input lines and processor control signals.
  • 4V to 5.5V input
  • (2) 70-pin AVX 5602-24 connectors
  • 118.3mm x 67.25mm
  • Four (4) x #0 mounting holes for direct connection to an Overo COM
  • Four (4) x #2 mounting holes to secure Palo 43 inside a casing

OK - Great! There is an LCD display and interface board for the Gumstix Overo line! I thought that was wonderful, until I started using it that is. Don't get me wrong - it works as advertised and does a decent job. It's just that I wanted something with a wee bit more resolution than is afforded by the Samsung display. 480 X 272 may be great for a smart-phone but this is a full blown computer system and I want MORE resolution!! (grin).

In my search for a higher resolution LCD display I ran across a question asked by someone else on the Gumstix forum. For those who don't know the Gumstix forums contain a wealth of information about the Gumstix Overo COM line of computers and the expansion boards. This is a meeting place where developers and hardware designers go to bounce questions off each other and where the Gumstix software developers hang out (and answer questions too!). To really glean the benefits of the forums I would strongly suggest using the "search" capabilities of the forums to find answers to questions FIRST! From what I have seen there are more repeat questions because people don't search for the answer first - it probably has already been asked and answered multiple times on the forums!

The question on the forum was about the possible use of a different Samsung LCD display with touchscreen capabilities but this display is 800X480 instead of 480X272. The part number of the display is LMS480KF02 with the following specifications:

LMS480KF02 is a TMR(Transmissive with Micro Reflective) type color active matrix
TFT (Thin Film Transistor) liquid crystal display (LCD) that uses amorphous silicon TFT
as a switching devices. This model is composed of a TFT-LCD module, a driver circuit and a back-light unit. The resolution of a 4.8" contains 800 x 480(RGB) dots and can display up to 16.7M colors.

- Triple-Gate Technology applied
- Transmissive with Micro Reflective type and Back-light with LED is available.
- TN (Twisted Nematic) mode
- 24bit RGB Interface
- Back Light with 14 LEDs (Light Emitting Diode)

Display terminals for PMP(Portable Multimedia Player) , Portable CNS(P-CNS) ,
AV , UMPC (Ultra Mobile PC) application products.

Hmmm - this may be the answer I am looking for!

Looking at the two display's specifications and drawings indicated they are basically the same in terms of electrical connections - they both use a flexible circuit board with a 45-pin connection for the electrical signals. Both have the same electrical connection layout (with one or two exceptions for the signal definitions but they look equivalent). The biggest exception is the Gumstix Samsung display uses a single string of 10 LED's to provide the LCD back light whereas the possible replacement LCD uses two strings of 7 LED's for the back light. I have not determined if this will be an issue yet or not. The LED back light power supply on the Palo-43 board is rated for up to 40-Volts maximum and up to 1.2-amps of current. I suspect I will need to wire the backlight LED strings in parallel with a ballist resister in each string to run all the back light LED's on the replacement board. I suspect wiring in series will raise the total forward voltage required too high approaching the maximum voltage rating of the PWM Boost-Switching Regulator on the Palo-43 board. Both Blue and White LED's tend to have around a 2.5V - 2.8V forward voltage drop so fourteen LEDs in series would present a 35V to 40V or greater voltage requirement to drive the LED string. This is too high for the boost-voltage regulator to handle. Wiring the LED strings in parallel with a ballist resister in each string would lower to total voltage requiement to approximately half that of the series string. Increasing the total current to drive the two strings is not a problem - all that is required is to replace the 10-ohm feedback resister with something a smaller value resistor - say 5 to 7 ohms which would give around 30 - 40 ma of LED current total. Driving each string at around 20-ma is a good compromise for light intensity vs longivity of the LEDs.

For those interested the regulator is the Micrel MIC2297 and you can find the specification sheets on the Micrel website (gotta love the Internet!). Here are the condensed specifications for the device:


2.5 to 10V input voltage range
Output voltage up to 40V
1.2A switch current
600KHz PWM operation
Trimmed 200mV feedback voltage
OUtput over voltage protection (fixed or adjustable)
PWM Brightness Control
DAC Brightness Control

The following chart shows the pin out of the LCD display sold by Gumstix along with differences between the 4.3-inch LCD and the 4.8-inch LCD displays.
Note the pins highlighted in RED.

Gumstix 4.3-inch LCD electrical pin out chart

Pin# Symbol Function Remark

1 VSS Ground
2 VSS Ground
3 VDD Power Supply (2.5 or 3.3V)
4 VDD Power Supply (2.5 or 3.3V)
5 R0 Red Data (LSB)
6 R1 Red Data
7 R2 Red Data
8 R3 Red Data
9 R4 Red Data
10 R5 Red Data
11 R6 Red Data
12 R7 Red Data (MSB)
13 G0 Green Data (LSB)
14 G1 Green Data
15 G2 Green Data
16 G3 Green Data
17 G4 Green Data
18 G5 Green Data
19 G6 Green Data
20 G7 Green Data (MSB)
21 B0 Blue Data (LSB)
22 B1 Blue Data
23 B2 Blue Data
24 B3 Blue Data
25 B4 Blue Data
26 B5 Blue Data
27 B6 Blue Data
28 B7 Blue Data (MSB)
29 VSS Ground
30 PCLK Pixel Clock
31 PON Display on/off
32 HSYNC Horizontal Sync Signal
33 VSYNC Vertical Sync Signal
34 DE Data Enable
35 PWRSEL VDD power select (High:3.3V / Low:2.5V)
36 VSS Ground
37 Y2 Y_Up
38 X2 X_Left
39 Y1 Y_Bottom
40 X1 X_Right
41 VSS Ground
42 VLED1- LED 1 Cathode
43 VLED1+ LED 1 Anode
44 NC Non Connected
45 NC Non Connected
The three red highlighted lines in the pin-out listing above are the differences between the two displays. Pin-35 on the Gumstix LCD is used to inform the circuitry on the LCD that the power supply voltage is 2.5 or 3.3VDC - on the 4.8-inch LCD pin-35 is ground! DO NOT CONNECT the 4.8-inch LCD directly to the Palo-43 as this will short out the 3.3-VDC power buss on the Palo-43 board. I am looking into a mod for the board that will allow either LCD display to be connected without causing problems with the 3.3-VDC buss.

As for pins-44 and 45. On the 4.8-inch LCD display these pins are used for the second back light LED string. I have not checked to see if one string will light up the LCD panel - if it will then the use of the second LED string may not be required - otherwise I will need to connect the two pins correctly in parallel with pins-43 and 43 to power the second LCD string on the backpanel. Of course this will require a ballast resister in series with each LCD string to keep a current balance between the LCD strings but this is not a very difficult thing to do.

Stay tuned - more to follow....


I modified the 4.8-inch LCD display by cutting the copper trace running to pin-35 on the LCD connector (quick fix) to test and see if the LCD display would indeed work. After cutting the copper trace near the connector (end of flex board) I checked for any possible short-circuits I might have caused (.5mm traces are really small!) and after I was curtain I had not inadvertently caused any issues I inserted the 4.8-inch LCD flex board connector into the Overo Palo-43 LCD interface board. I have an Overo Earth COM installed on the Palo-43 board for testing and the original factory firmware is still installed in the NaNd Flash memory on the Overo Earth board.

I powered up the Overo boards using a 5.0-VDC power supply (obtained from Gumstix) and the
4.8-inch LCD panel lite up using just one LED string (there are two in this LCD display) but it could be brighter (grin). After a couple of seconds (about 15 or so) the Overo Earth GUI displays on the LCD panel! Success! This panel works with the Gumstix Palo-43/Overo COM computer modules with minimal modifications! Pin-35 is the only thing that actually has to be modified in order to get this LCD panel to work!

As you can see in the image on the right the display settings within the uboot and kernel have not been changed from the default 1024 X 768 display settings but that is something else to do so the displayed resolution matches the LCD display resolution. One other thing to notice from the images - at the bottom of the display you can make out a slight darkening along the bottom edge of the display. If you look really close you can see there are seven slightly darker areas along the bottom edge. I am thinking these are the un-lite LED's in the second string. For normal operation I don't see it as a problem but if you are in a well lite room you may want the second LED string powered up.

Now, instead of a 480 X 272 LCD display I have a 800 X 480 Display (4X more display info) so can now do many more things with the computer system (better, fine-resolution graphics comes to mind).

Hopefully this blog posting will be useful to others working with the Gumstix Overo line of COM modules!

As a side note for those of you "Green" people (grin) - a Gumstix Overo Earth mounted on the Palo-43 board using the 4.8-inch Samsung LCD display with one LED string lite draws about 2-watts of power at 5-VDC. Not bad at all.

Let me know what you think! Leave a comment (good, bad or indifferent).

Thursday, June 25, 2009

Too many Directions!

In working with the Overo COM line I have come to a revelation.... well.... more of an observation really.

My revelation is this:

There are so many more possibilities as to what can be done using the Overo COM line of computers than can be accomplished by one person!

DUH! one might say - that is obvious. What really brings it home for me is looking at the computer itself with all of the different capabilities built into it's design. This machine has so many different interfaces built into it's design Gumstix had to settle on a sub-set of the interfaces to bring out to the outside world! I suspect they would have had to make the COM board bigger if they wanted to bring all of the capabilities out from the OMAP Cortex-8 processor just because there is no physical way to have the interfaces access the outside world through the two 70-pin connectors on the current boards. Too bad as there are other interfacing capabilities on the OMAP processor that are not accessible.

OK - So now you have some idea of the quandray I face - so many possibilities, so little time! the following is a partial list (as I am sure you can come up with ideas I have not even considered) of things I want to do with this machine....

1. Intellegent firewall/router/access point.
There is no reason the machine could not handle this sort of application - it is based on Linux and there are all sorts of applications to implement a firewall/router/wireless access point using the Overo COM computer.

2. Wireless MESH-Based communications data collection & processing system.
This is one neat idea as what I envision is the COM system configured to run wireless communications between multiple COM machines and using a MESH network for redundancy of the network link. Given the computing power of the OMAP-3 processors and using the 3530 gives the ability to perform DSP based processing one should be able to come up with all sorts of monitoring/control system ideas for this computer. Heck, you can even have a display using the machine's video capabilities for such things as process control and monitoring. Talk about inexpensive control systems!

3. Intrusion Protection System.
Hmmm - How about a computer system small enough to fit in a cigarette case but able to detect unauthorized access to a network - maybe even able to thwart a hacker attack on a network too. There are software applications for linux that allow monitoring and intrusion prevention (using firewall controls) that can run on the COM machines. At 600-MHz the COM machines clock is faster than a Cisco PIX-515 firewall if that gives you any idea of the capabilities. I know - this is an ARM based RISC machine - so what - it is still FAST! (grin).

4. Intertial Navigation System.
This is an interesting idea I had. There is enough compute power and interfacing capabilities in the COM machines to build an inertial Navagation system! At first I thought it would cost an arm and leg to build such a device as the cheapest one I could find on the Internet runs more than $4000 USD. Well - a little research reveals you can obtain the hardware for a GPS, 3-Axis Magnatometer capable of very low magnetic field measurements down to 0.015 u-Tesla and a 6-degree of freedom solid-state gyro/accellerometer package for less than around $200 - $250 USD! Given the Earth's magnetic field ranges from around 30 - 60 u-Tesla there is no problem in detecting the direction/orientation of the Earth's magnetic field! With a GPS, Magnatometer and gyro/accellerometer package you can build your own inertial navigation system that rivals most expensive packages for a small fraction of the cost. What can you do with such a system??? How about sailboat autopilot? UAV anyone?

5. Magnatometer Mapping System.
Building upon the inertial Navigation System you could use the 3-axis magnatometer output along with the GPS information to produce a map of the magnetic field in an area - by moving back and forth along a line and sweeping the area and given you know the orientation and direction of movement based on the sensor inputs from all of the sensors and GPS you can draw a "map" of the earth's local magnetic field strength and orientation relative to the sensing system over a given area. Basically you have a method to detect iron/steel objects by the affect they have on the local magnetic field. Buried treasure anyone???

6. Perimeter Monitoring System.
An interesting thought here. Why not use the COM machine as a perimeter monitoring system. Since you can get a LCD display for the COM machine you could actually "draw" the perimeter you are monitoring on the display then change icons/colors to denote where things are happening. By using wireless sensors and coupling back to the COM using wireless communications you could actually deploy a monitoring system rather quickly. I am not delving too much into the details here but there are all sorts of possiblities!

7. Home Entertainment System.
I follow several forums such as the Gumstix and Beagle-Board Forums and I get this idea from the Beagle-Board forum. Seems there is an effort out to build a home entertainment system based on the linux operating system. This would be a natural thing for the COM computer as it runs linux. The really nice thing is the Gumstix Overo line and the Beagle-Board both use the same OMAP processor (at least the OMAP 3530) so the same applications software will run on both boards. Granted there may be some small differences but for the most part there is very little difference as far as applications software is concerned. One such application is a home entertainment system - it is in development on the Beagle-Board so should port directly over to the Overo COM machines too (grin).

8. Home Control/Monitoring System.
This idea is a combination of the perimeter monitoring system and the home entertainment system. Why not combine them to have a total home control and monitoring system - you would use the television as the display for the system when you needed to check on it and then could watch movies played through the COM board or TV from an external source. All you have to do is use your imagination to come up with all sorts of possiblities!

As you can see I am having a great time coming up with ideas - now all I need is the time to work on them! Hopefully in the coming months I will actually have the time to put into implementing some of the ideas mentioned here. As I work my way through them I plan to post the information here so others may follow along and hopefully make some improvements on my initial implementations! That is what public domain software/hardware is all about - improving upon ideas! Everybody comes out ahead!!!

I thought of some more ideas and have listed them below but did not expand on them - see what you can come up with for them and let us know! Who knows - you may come up with the next killer application!!!

9. Network Monitoring System.

10. Communications System.

11. VoIP PBX System.

Your Ideas here.

As you can see - If you can dream it you can do it! All it takes is just some common sense and a will to succeed. It also helps if you have an understanding of the projects and know where to find the parts. Comments??? Ideas??? Let me know!!!

Friday, June 5, 2009

Working on the development side of things

For the last several weeks I have been working on the development side (software implementation) for the Overo series of COM (Computer On Module) units. This has been rather an interesting experience as the Overo line is a rather new (read: bleeding edge) computer system so the software is being created in a very fast pace in terms of development. Unlike a Windows based machine you have to run a development system to implement different applications or make changes to the Linux kernel for different hardware drivers if they are not active in the factory installed version. You can installed pre-compiled applications using an application installation program but if the application is not already built or you are wanting to use a linux hardware driver that is not already factory installed then a development system is a must. Besides, it can be very educational to see how things are done under the hood, so to speak. The development system chosen for the Overo line by Gumstix is called OpenEmbedded which is an open source development system for embedded computer systems (interesting - wonder where they came up with the name?).

Until now I have worked with cross-compiler systems where you were actively involved in the cross-compile process, such things as creating and modifying 'make' files (used to setup dependencies, setup variables used, call the different development applications and so on) to installing the different cross-compiler and library files and compiling the different parts of the development system toolchain. Most of the development systems I have worked with also require "switching" to a virtual filesystem for the actual cross-compilation process to protect the underlying operating system otherwise it is very easy to trash the operating system and crash the development computer system!

In using the OpenEmbedded system that has totally changed! Most of the 'grunt' work is now handled by the OpenEmbedded system itself, from downloading the different parts needed to cross-compile C source code, compiling the cross-compiler tools and software libraries, installing the different parts used in the proper locations within the development computer's filesystem, downloading the different applications and Linux kernels used for creating the operating system and applications, determining the different dependencies (which parts need to be compiled in what order so the different parts and applications can 'find' the needed links and library headers) - then - building the whole operating system and applications along with the filesystem, boot-loaders and startup scripts needed to run the system and applications on the Overo line of computers! Gotta love that! Now - the learning curve for OpenEmbedded is steep (at least it is for me) but is very doable and if you do become accomplished at creating bitbake recipes (recipes are the script files that tell BitBake how to accomplish something) you can build most any application without the laborious task of writing 'make' files.

Now - this is the part most here will find difficult. The OpenEmbedded system runs on Linux systems ONLY! Part of the reason for this is most of the embedded computer systems working with open source are based on Linux so it makes sense to develop in the same environment as the target system operating system is going to be. OpenEmbedded will NOT work in Windows (unless you are running a Linux system on a Windows based machine)! This may change in the future but I would rather stay in the Linux environment so as not to muddy the water too much - just think of the headaches you might encounter trying to run Windows compilers to build Linux operating systems on computers that have a whole different architecture from the machine the target system is targeted to! This is not as bad as it might seem! My home development system IS a Windows based system ( I like gaming and most of the games I play are not written to run in Linux!) but I can run Linux on the system without any issues and still perform other tasks in Windows at the same time.

How can this be you ask?

Simple - in one word - Virtualization!

I use VMWare's free VMWare Server to run different "Virtual" computers on my Windows system. This allows me to have multiple computers exist on the same hardware and I have enough computer resources to run Windows (XP) and three or four virtual machines at the same time on my machine. Of course it can get confusing at times but the capability is there (grin). Now there is a caviat to using a virtual environment... you want to have enough physical resources on your machine to allow the virtual machine to run decently. In other words you want to have at least 1-gig of RAM and at least 100-Gigs of hard drive space available otherwise if you have only minimal RAM in the machine the virtual machine may not have enough memory and will start swapping to the virtual drive (this really bogs things down) and if you don't have enough hard drive space you will "run out" of virtual hard drive space in the virtual machine - this is worse than too little memory! Having said that here is what I did to create a development system for the Overo line.

Here are the (very) generalized steps I used:
  • Downloaded the Free VMWare Server and installed it on my computer system. The VMWare server also needs the Java Runtime package so I downloaded that as well then installed it on my machine per the instructions on the Java website.

  • Once I had the VMWare Server installed I opened the VMWare Server application and created a virtual machine for a Linux System. I setup the memory for 512-Megs to start and configured the hard drive storage for 80-Gigs of space. For the 'network' settings I use 'bridged' mode so the virtual machine would use the computer's interface and the virtual operating system would be able to use DHCP to obtain the information needed to connect to my home network automatically. The configuration for the virtual machine is stored on the hard drive a several files (this includes the virtual hard drive image) which makes saving copies very easy - just copy the files and you have a backup!

  • The Linux environment I use is Ubuntu Linux workstation. I downloaded the Ubuntu 9.04 version (latest stable version) as an ISO file (CD image file) and saved it on my machine in the directory where I built the virtual machine for the development system. The reason you save the ISO image in the same location as the virtual machine storage is very simple - in the VMWare Server environment you can only "see" items that are stored in the virtual machine directory!

  • To install the Ubuntu 9.04 Workstation software in the virtual machine you need to configure the CD-Rom drive settings in the VMWare Server settings for the virtual machine to use the ISO image as the CD-Rom. This is very easily done during the configuration of the virtual machine as there is a question during the configuration as to what to use for the CD-Rom - you just select the Image setting and browse to the Ubuntu ISO image file previously saved in the virtual machine directory - this is the only place you can browse from within the VMWare Server which is the reason I saved the ISO file there.

  • Once the virtual machine was configured I started the virtual machine and opened a virtual machine window. The Ubuntu system starts up just like the CD version - I selected the "Install Ubuntu" selection to install the Ubuntu system in the virtual hard drive. After answering a couple of questions (keyboard and mouse type, timezone, user name and password, etc ) the Ubuntu installer fires up and completes the installation of the Linux system into the virtual hard drive and then waits for you to "remove" the CD-Rom media and reboot the virtual machine.

  • To "unmount" the Ubuntu ISO you just edit the CD-Rom settings for the virtual machine in the VMWare Server and set the CD-Rom to either none or the physical one in your machine (personally I set it to the physical one). Ubuntu will complain since it was running from the ISO image but just answer "yes" to the question then reboot the virtual machine. When it comes back up you will be running in Ubuntu 9.04 (or whatever version you are using) Linux in a virtual environment!

  • After Ubuntu was installed on the virtual machine I performed a system update to download any new updates for the system. While this is not a hard requirement I like to have a system that is fully up to date before using it for development.

  • The next step is to install the Openembedded development system in the virtual machine. I used the steps located on the Overo Development Website (Link) but there are a couple of differences for the Ubuntu 9.04 version:

    1. One has to do with the notes on the webpage where the instructions state to add the following to the sysctl.conf file; 'vm.mmap_min_addr = 0' . The sysctl process does not recognize this command so I left it out where the instructions stated to place the command.

    2. A second item has to do with the 'way' the development system operates in the current default download of the OpenEmbedded system. BitBake (the MetaData executor) and OpenEmbedded use Python ( a programming language) to implement the development system - the default download configures the system to use "Python" whereas the Ubuntu system uses "Python-2.6". How can that be an issue - it is as the system gets 'confused' as to which version to use - talk about making a mess! Also, it is very difficult (at least for me) to determine exactly what fails during a build when this confusion occurs. The answer to this issue is really simple - just update the OpenEmbedded development system. If you follow the instructions to install the OpenEmbedded system I listed earlier then all you need to do is go into the directory and type the following command: git update which downloads the current updates for the OpenEmbedded system. One of the updates corrects the Python "confusion" issue so things work properly after the updates are done. NOTE: I am being metaphorical here when I say it is a "confusion" issue but it makes it easier to describe (grin).

    3. When you reach the point where you perform your first build be prepared to wait a while for it to complete! On my system, connected to the Internet at 8-mbit/second it takes about 12 hours for the development system to download all the parts needed and compile the console (CLI) version of Linux for the Overo computers. Once you have performed a successful first build the time is much shorter as all of the development parts have been downloaded and compiled and all of the source files for the console version are on your virtual hard drive.

  • Once the development system has been installed and you have built the first recipe (omap3-console-image) successfully you can build the GUI desktop version for the Overo line by using the 'bitbake omap3-desktop-image' command in the overo-oe directory of the developement system. Of course, if you have not built the development system and are just reading this that last sentence probably will make absolutely no sense what-so-ever! (grin). A note - there are a great many parts to the GUI version that have to be downloaded so this first build also takes a fair amount of time! On my system the combined first build of the console and GUI versions took about 26-hours total to accomplish. Of course, your time will be different based on your computer hardware and your internet connection.
If you do decide to setup a development system for the Overo line I would advise you insure you have enough memory and hard drive space! On my system the GUI version of the Linux operating system for the Overo line takes about 22-gigs of space. If I wanted to build ALL of the applications and drivers currently available it would require around 40 - 45 gigs of space to store all of the information needed.

I am thinking if there is some interest I could create a VMWare image of the development system with the OpenEmbedded and BitBake applications installed. The VMWare image would already contain the all of the OpenEmbedded updates at the time of the image build. All you would need to do is download and install the VMWare Server software, install the image then perform the console and GUI bitbake builds to have a Overo development system of your own. Let me know what you think...

Saturday, April 4, 2009

New Overo Computer On Module!

Gumstix has come out with the Overo Fire COM - Gumstix now is calling them "Computer on Module" to differentiate what is the motherboard and what is the daughterboard - must have been some confusion between the computer board and expansion boards.

The Overo Fire COM is the top of the line in the Overo series, at least at the moment. It contains not only built-in Wifi 802.11b/g capabilites but also BlueTooth capabilities on board. This feat of magic is provided by a Marvell W2CBW003 integrated circuit (can be seen on the left side of the board in the picture) which connects to an external WiFi and BlueTooth antenna (not supplied) through a u.fl R.F. connector for each one. Even though the WiFi/BlueTooth radio Integrated Circuit package is only 12-mm x 12-mm in size it packs a great deal of capability. For those in the know - this is the same radio integrated circuit that is on the Beta Overo board and all the software drivers already exist in the operating system installed on the Overo boards. Couple the WiFi and Bluetooth capabilites with the TI OMAP-3530 processor on the Overo Fire COM and you have one very capable device in a very small form-factor! The only thing missing is a video out source on-board to make this a completely self-contained computer system! For video and USB access you will need one of the expansion boards mentioned below or build your own custom interface board.

I have discussed some of the capabilities of the TI OMAP-3530 processor in a previous posting so willl not delve into that portion again - I do want to talk a little about the Wi2Fi (Wireless 2 Wireless ) capabilites on this board. The W2CBW003 high-level block diagram is to the right.

Even though the block diagram shows 802.11a/b/g that is not the case with the W2CBW003 - it does not have 802.11a capabilities. I suppose this block diagram is used for a different radio integrated circuit and someone just got lazy! (grin). Not having the 802.11a capability will, in my opinion, limit the usefulness of this combination as more 802.11a access points are becoming prevealent - especially in areas saturated with 802.11 b/g and wireless phones, baby monitors and the like exist. Hopefully Gumstix will realize this fact and talk to Marvell about a WiFi/Bluetooth integrated circuit combination that is pin-to-pin (or should I say "Ball-to-Ball in reference to the methodology of mounting the integrated circuit to the circuit board) compatable so it is a direct replacement for the current 802.11 b/g configuration - I don't believe Marvell has such a device out yet but judging from the block diagram they may be working towards that goal.

The Overo Fire COM is the same physical size and electrical connection specifications as the original Overo Earth board so will work with the Summit Expansion board. Speaking of expansion boards Gumstix has come out with a few more in different configurations for the Overo COM series:

The Summit expansion board:
This is the first expansion board available for the Overo COM series - I have already discussed this board earlier so will not bore with details (grin). One thing I will say is it is the least expensive of the expansion boards and packs a good number of interfaces on-board for general purpose use. The only exception is a built-in ethernet connection but that is now covered by the Tobi board (see below).

The Palo-43 expansion board:
The Palo43 is a new expansion board for the Overo COM series of processor boards and works with all of the Overo COM boards. The Palo43 contains an LCD interface which will drive the Samsung P/N: LTE430WQ-F0C (available from Gumstix at a very reasonable price in single-unit lots) and a touch-screen controller to interface to the touch-screen resistive overlay on the Samsung LCD display. The board also contains most all of the interfaces contained on the Summit board thus it gives you the capabilites of the Summit expansion board with a self-contained LCD Touch-Screen capability. The Palo43 does not have a video output like the Summit expansion board (for obvious reasons). A second difference is the physical locations of the different interface connections - they have been moved to each end of the board to allow the additional circuitry needed to drive a LCD display. Since these systems are targeted at development this is usually not an issue (grin). One interesting note - the description of this board lists it's size as 80-mm X 39-mm but that is not the case given the size of the ports are the same as on the Summit expansion board.
UPDATE: The powers that be at Gumstix have determined there were some errors inadvertently incorporated within the description of this board. The actual size is 118.3 x 67.25mm and is reflected on the Gumstix website as well. Talk about quick response!!! Less than one day! These guys really do care!

The Tobi expansion board:
The Tobi expansion board is the third in the Overo COM series of expansion boards. Like the Summit expansion board it contains Audio Sterio Input and Output connections, High-Speed Version-2 USB-OTG and USB Host ports, a HS Version-2 USB Console port, 5-VDC Power Connector and the 40-pin connector location to access the different interfaces provided. In addition to all of the above interfaces the Tobi also has a 10/100 megabit, full-duplex Ethernet port on board as seen on the right side of the circuit board in the image to the right. You can check out the specifications for the port here: LAN9221 The physical size of the board is: 105 x 40mm.

Update: As of this moment (June 5, 2009) there is an Interference between the Overo Air COM and Fire COM modules with a component on the Tobi board. In other words you can not use a Overo Air COM or Fire COM with the Tobi board until Gumstix resolves this issue. What does this mean? You can not have 802.11b/g and Bluetooth capabilies on the Tobi board. If those are not a problem you still can use the Overo Earth COM and Water COM on the board without any physical component interference issues. In my opinion (for what it is worth) this really blows! I would want ALL capabilities available (wireless, bluetooth and ethernet) on the board for a full fledged computer in a very very small space, but that is just me.

Now - as of the date of this posting the Overo Fire and Overo Air (same as the Overo Fire but uses the TI OMAP-3503 instead of the TI OMAP-3530 processor) are out of stock. I suspect this will be cleared up in short order as I suspect there will be a good demand for the two COM boards as people find out about their capabilities and the fact they have WiFi and Bluetooth hardware already on the boards! Given the Overo Fire COM utilizes the TI OMAP-3530 which has video DSP hardware capabilites and OpenGL built into it things will get very interesting in the upcoming months as programmers start to bring out the capabilites of the Overo Fire COM board! These are indeed exciting times!
Mine is already on order!!!
If you would like to see more about this and the other Gumstix boards checkout this link:

As a matter of interest I have been in contact with the CEO of Gumstix and he is expecting the Overo Air and Fire boards to be available next week (April 13th, 2009) or there abouts.

Thursday, April 2, 2009

Now there is an Overo Water board out!

Stop the press! Stop the PRESS! (always wanted to say that)...

There is a new Overo board out - it is called "Overo Water"... Hmmm - seems like there is an Alchemy Theme going here! The Overo Water board is built on the same board as the Overo Earth. This is possible because the difference between the Overo Earth and Overo Water boards is the TI OMAP Computer on Chip integrated circuit which has the same pinouts.

The Overo Earth board comes with the TI OMAP-3503 integrated circuit with the RAM and FLASH memory contained in an integrated circuit mounted on top of the TI integrated circuit, called a "Package on Package" or POP configuration. The Overo Water board comes with the TI OMAP-3530 integrated circuit with the memory in the same configuration.

There are a good deal of similarities between the two TI integrated circuits but there are also some very distinct differences:

To the right is the hi-level block diagram of the TI OMAP-3503 integrated circuit. Most, but not all of the functionality of the integrated circuit is accessible on the Overo Earth or Overo Water board - this is because of the actual physical size constraints of the two boards - there just is not enough real estate to have all the capabilities available external to the TI OMAP integrated circuit. This is really not a limitation to the capabilities of the computer board as most of the really useful functionality is directly or indirectly accessible on the expansion board (Summit Expansion board) and if the Summit board does not make the specific function you are looking for accessible but it is available on one of the two 70-pin connectors on the computer board you can either fly-wire the connection on the summit board (really tricky to do) or have a custom board fabricated with the functionality accessible (pricey but possible).

The hi-level block diagram for the TI OMAP 3530 looks a great deal like the TI OMAP 3503 (after all they are in the same Applications Processor Family) but you will notice there is a dedicated Video processing section in the TI OMAP 3530 that does not exist in the TI OMAP 3503! This difference is BIG as it allows the Overo Water board to perform some video magic the Overo Earth would have problems with!

If you notice on the upper left there is a block that is dedicated to Video processing and Audio processing that does not exist in the previous block diagram of the TI OMAP 3503 processor. This is hardware video acceleration which is completely distinct and separate from the ARM 7 processing core. What this does is allow the video processing to be performed in parallel with the running of applications so speeds up the video capabilities quite a lot! The TI OMAP 3530 has some very impressive capabilities in the video department as compared to most other embedded computer systems:

High Performance Image, Video, Audio (IVA2.2™) Accelerator Subsystem
430-MHz TMS320C64x+™ DSP Core

  • Enhanced Direct Memory Access (EDMA) Controller (128 Independent Channels)
  • Video Hardware Accelerators

POWERVR SGX™ Graphics Accelerator (OMAP3530 Device Only)

  • Tile Based Architecture delivering 10 MPoly/sec
  • Universal Scalable Shader Engine: Multi-threaded Engine Incorporating Pixel and Vertex Shader Functionality
  • Industry Standard API Support: OpenGLES 1.1 and 2.0, OpenVG1.0
  • Fine Grained Task Switching, Load Balancing, and Power Management
  • Programmable High Quality Image Anti-Aliasing

Fully Software-Compatible With C64x and ARM9™

Commercial and Extended Temperature Grades
Advanced Very-Long-Instruction-Word (VLIW) TMS320C64x+™ DSP Core

  • Eight Highly Independent Functional Units
  • +Six ALUs (32-/40-Bit), Each Supports Single 32-Bit, Dual 16-Bit, or Quad 8-Bit Arithmetic per Clock Cycle
  • Two Multipliers Support Four 16 x 16-Bit Multiplies (32-Bit Results) per Clock Cycle or Eight 8 x 8-Bit Multiplies (16-Bit Results) per Clock Cycle
  • Load-Store Architecture With Non-Aligned Support
  • 64 32-Bit General-Purpose Registers
  • Instruction Packing Reduces Code Size
  • All Instructions Conditional

Additional C64x+™ Enhancements

  • Protected Mode Operation
  • Exceptions Support for Error Detection and Program Redirection
  • Hardware Support for Modulo Loop Operation
  • C64x+ L1/L2 Memory Architecture
  • 32K-Byte L1P Program RAM/Cache (Direct Mapped)
  • 80K-Byte L1D Data RAM/Cache (2-Way Set-Associative)
  • 64K-Byte L2 Unified Mapped RAM/Cache (4-Way Set-Associative)
  • 32K-Byte L2 Shared SRAM and 16K-Byte L2 ROM
  • C64x+ Instruction Set Features
  • Byte-Addressable (8-/16-/32-/64-Bit Data)
  • 8-Bit Overflow Protection
  • Bit-Field Extract, Set, Clear
  • Normalization, Saturation. Bit-Counting
  • Compact 16-Bit Instructions
  • Additional Instructions to Support Complex Multiplies

The above information only "touches" on the capabilities of the TI OMAP 3530 integrated circuit - for a complete list check out the TI site here:

This thing is Packed for Graphics processing! TI (Texas Instruments) says it best:

"OMAP3530 and OMAP3525 high-performance, applications processors are based on the enhanced OMAP™ 3 architecture. The OMAP™ 3 architecture is designed to provide best-in-class video, image, and graphics processing sufficient to support the following:

  • Streaming video
  • 2D/3D mobile gaming
  • Video conferencing
  • High-resolution still image
  • Video capture in 2.5G wireless terminals, 3G wireless terminals, and rich multimedia-featured handsets, and high-performance personal digital assistants (PDAs).

The device supports high-level operating systems (OSs), such as:

  • Windows CE
  • Symbian OS
  • Linux
  • Palm OS "

Nuff said! Once I have my hands on this puppy (Overo Water), which is on order and on it's way from Gumstix to me, I plan to do some interesting 2D/3D programming to see how well it handles some games - one of which is Quake-1 ( a very FAST FPS game).

More to follow! Stay Tuned! (always wanted to say that too).

Tuesday, March 31, 2009


One of the things I want to do with this tiny computer system is build a PWCS (Personal Wearable Computer System) [I just made that up - like it?]. In order to do this I needed "something" to mount the actual computer system in and keep it's size down to a minimum. Currently there is no case for the Overo Earth computer as it's original design is for embedded applications, and I don't think they had "embedding within clothing" in mind when it was designed (grin).

I could have used most anything to make a case for the micro-beast (that is the Nickname I have for the machine). At first I thought about building up a case using either brass or thin copper and putting my "Leet" soldering skills to work but then realized that would not only be a little expensive (given the price of brass and copper sheet now days) but would have looked rather "tacky" as well - solder beads along seams just are not the same as welded ones (grin).

Next stop - the local Radio Shack store to see what they might have. That was a rather good choice as they have a 4-inch by 2-inch by 1-inch (10.16 x 5.08 x 2.54-cm for you metric geeks) Plastic Project Enclosure with a choice of aluminum or plastic lid (comes with both) for about $3.00 (USD).

Radio Shack Model: 270-1802 Catalog #: 270-1802

Since the enclosure is made of plastic it was rather easy to 'carve' the connector holes in the case with an X-Acto Knife (just be careful not to slice and dice yourself). Now - while I can solder with the best of them my X-Acto Knife skills leave a "little" to be desired! Who cares! Not me!!! It got the job done!

Here is my Overo Earth/Summit board (micro-beast) mounted in the enclosure. As you can see access to all of the "standard" interfaces is available from outside the case. Even the console USB connection is possible through the cutout in the back of the enclosure. I have not configured anything to access the 40-pin connections (yet) but that is a future project. There was a fair amount of modification to the stock case to mount the board in the enclosure - there are stand-offs in the case in totally the wrong locations that had to be removed and there are "slide-slots" running from the top to the bottom of the enclosure that have to be carved away but I think the effort was worth it - especially since there is not a commercial case for the board.

Now that I have the "computer" mounted within a case to protect it the next order of business will be to build the "world" interfaces for it. That will be the subject of a future blog entry!

Does Size Matter - You Bet It Does!

OK - I guess the title could be read as "something" from a certain type of "Television Commercial" but I could not resist!

The Overo Earth, mounted on the Summit Expansion board is still a very small computer system. If you don't believe this statement then take a look at the picture to the right!

Yes - that is an American Quarter and that is a Double-A (AA) Ni-Cad battery below the board.

If you look real close you can make out the outline of the actual Overo Earth board - it is just below the 40-pin holes under the Quarter and above the audio, HDMI, USB Host connectors on the Summit Expansion board.

The configuration shown in the picture is the most likely one most hobbiests or experimenters will use. You don't have to have "Leet" soldering skills or Microscopic Vision to build and solder the 70-pin connectors to access most of the capabilities of the Overo Earth computer - and - as a bonus you have video, audio, USB and console access directly off the Summit Expansion board - not to mention you don't have to build power conversion circuits for the 3.3-VDC/1.8-VDC power supplies needed to run the Overo Earth computer. For the price the Summit Expansion board is well worth it - just in the reduction of the "frustration factor" alone.

If you decide to access some of the more interesting interfaces, such as the SPI, I2C, 1-wire, PWM, ADC and the rest of the input/output connections brought off the Overo Earth computer you will need to keep the following points in mind:

  1. All of the voltages to the different interfaces are 1.8-VDC. If you exceed this by very much you probably will let the "magic smoke" out of the Overo Earth OMAP-3503 integrated circuit as most of the interface connections go directly to the integrated cirtcuit.
    ( I will be describing a method to "translate" the 1.8-VDC logic levels to something more in line with current inexpensive sensor technologies - read: 3.3 - 5.0 VDC in a later blog entry)

  2. You will need to supply the power externally to any interface devices you want to connect to the Overo Earth computer interfaces - the Overo Earth computer does not have the additional power capacity to run very many sensors, if any at all. The on-board power regulator does not have much additional reserve power capacity so it would be wise to power external sensors with an external power source.

  3. If you decide to put a socket in the 40-pin holes on the Summit Expansion board instead of soldering wires directly to the hole locations put the socket on the BOTTOM side of the expansion board. The reason for the bottom placement location is to allow you access to the micro-SD location without requiring the removal of the Overo Earth computer from the Summit Expansion board. The 70-pin connector connections are pretty fragile and each time you remove and insert the Overo Earth on the Summit Expansion board you run a risk of damaging one or both 70-pin connectors. Better safe than sorry!

Sunday, March 29, 2009

Overo Connections - reaching the outside world....

While the Overo Earth computer, in it's present form, has a great potential for all sorts of applications it has a "minor" drawback... Very little in the way of outside communications! While the computer has two 70-pin connectors with all sorts of input and output capabilities most, with the exception of companies with the skilled workforce, will have problems connecting to the computer!

To aleviate this problem Gumstix has an expansion board the Overo Earth plugs into that brings all sorts of connectivity to the miniscule computer board - Enter the Summit Expansion Board.

As you can see from the image to the right there are several connecitons available on the expansion board that allow you to access different aspects of the Overo Earth computer:


  1. USB OTG mini-AB

  2. USB host mini-A (experimental)

  3. DVI-D (HDMI) video out

  4. Audio In / Audio Out (stereo)

  5. USB Serial Console

  6. 40-Pin connector location on board
    (Signals available on 0.100-inch through-holes at 1.8V logic levels)

  • Two (2) two-wire serial ports

  • One 1-wire port

  • 6-ea. PWM output lines

  • I2C port

  • SPI Bus

  • 6 ea. A/D lines (at 1.8-V logic)

  • processor control signal lines.

Power: 4V to 5.5V input

Connectors: 2-ea. 70-pin AVX 5602-24 connectors
(interface to Overo Earth board)

Size: 80mm x 39mm

Mounting: Four (4) x #2 mounting holes

Points of Interest:

  1. As delivered the Overo Earth/Summit USB-OTG port is configured as a host port - you will need either a mini-A USB to mini-B cable (available from Gumstix for a reasonable price) or you will need to perform a modification (add a jumper) to the USB-OTG port. If you have really good soldering skills (the connector pins are really small!) you can put a solder bridge between pin-4 and pin-5 on the circuit board side of the USB-OTG connector to fool the computer into detecting a mini-A connector when you have a mini-B connector plugged into the USB-OTG port (this is exactly what the mini-A connector does). Personally I think it is better to just spend the small amount of money and order the correct cable - and if you plan to use the USB Host connection you will need a mini-A to mini-B cable anyway as the USB Host connector is designed for mini-A USB connector ONLY.

  2. While the video output port is labeled "HDMI" and the Overo Earth is capable of HD-720P the factory configuration is currently 1024 X 768. If you want a different resolution you will need to setup a development environment and recompile the kernel to make the change to a different display resolution. If you don't have a monitor which supports DVI-D (or HDTV) then you will need to get a DVI-D to RGB converter to see the display.

  3. The USB Console port is just that - the console connection to access the Overo Earth operating system during bootup or as a local terminal. In the Linux/Unix world there is a "console" that can be seperate from the normal display, and usually is. This allows debugging and initial configuration or configuration changes without the need for the system to be booted completely up where the connected keyboard, mouse and or display may not be active yet. Normally you don't need to have a "console" connected but it sure can come in handy if there is no other way to communicate with the system (provided the operating system is running and recognizes the console). During the bootup process messages are printed to the console so this port is very handy during bootup troubleshooting.

Friday, March 27, 2009

So Little Info - So Much Capability!

The Overo Earth by Gumstix is a very powerful, and VERY small computer capable of performing a great many tasks - if you know how to use it!

My reasons for building this blog about the device are two-fold.

1. I needed a "place" to put information as I found it that would be rather safe and easy to access (beats doing backups all the time and I tend to reformat things a lot).

2. I wanted to "share" the information with anyone interested in it. From the discussions I have seen on some of the mailing lists dealing with the Gumstix machines I thought this would be a pretty good way of sharing the information.

As I find information I will be posting it here. Hopefully you will find it helpful or at least entertaining.

Now, one thing that should be pretty apparent is the Overo Earth computer does not have any obvious interfaces available to allow you to see the display (neither a console or video display), any form of recognizable connectors to allow you to connect a keyboard or mouse to the unit, nor any form of additional connectors for such things as USB or audio (microphone or headphone/speaker). Hmmm - all of that is actually available, but not in the "form" you are used to seeing! If you look real close at the picture you will notice two connectors on the bottom of the circuit board. Each connector is a 70-pin connector with all sorts of input/output connections to the computer system.

I know - you are probably thinking you have to fire up the ole soldering iron (micro-tip please), get out the microscope (these pins are REALLY REALLY SMALL!) and make an interface board just so you can use the computer. Well, you can do all of that if you want to but I am basically lazy and the ole eyes are not what they used to be! You can purchase an expansion board from Gumstix which already has the different interfaces built on-board and is also configured with a 5-VDC power supply that converts the 5-VDC to the 3.3-VDC needed to power the Overo Earth board. The Overo board has it's own 3.3-VDC to 1.8-VDC triple-converter built directly on the Overo Earth board but requires only 3.3-VDC to operate. More on this in a following posting as this is the key to allowing low-power operation that extends battery life.

The expansion board is called the Summit Expansion board and is directly available from Gumstix, the same folks who build the Overo Earth computer.