Design and document test power/radio cable

[gardners]

From the schematics, design and document a test cable that connects to the DSUB-25 port, and allows an ME2.0 prototype to be powered from any of the following:

1. 5V USB
2. 2x LiFePO4 rechargable batteries
3. Solar panel
4. 12V automotive power (car)
5. 24V automotive power (truck)

It should also:

6. Have connectors for the serial console for debugging/flashing, and the means to enable or disable looping the UART back into the unit to connect the serial console to an internal RFD900/RFD868 radio. A DPDT switch is probably the best option here.

7. Have 6 switches to allow pulling-down each of the RFD900/868 GPIO lines for radio country identification.

8. Have a connector that uses three of the RFD900/868 GPIOs to connect to a serial EPROM for sophisticated regulatory domain detection. An example serial EPROM to use would be a 24LC08B from Microchip (US$0.20 per piece):

http://ww1.microchip.com/downloads/en/DeviceDoc/21710K.pdf

9. Have momentary-action disconnect switch for each power source to test operation on power from the super-capacitor.