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:
- 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)
- 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.
- 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!