Bot-Logic expansion optionseach expansion board option XP1,XP2 and XP3 have two 6 pin connectors

these pins bring in the following pins for optional expansion boards it is and open expansion slot and boards can be made by anybody. the pin numbers are defined as follows:

1= IOREF, 2= POS5V, 3= VCC(3.3Vdc), 4= OPTION A-B-C, 5= Option A-B-C, 6=GND

7= GND, 8=SPI_MOSI, 9= SPI_MISO, 10= SPI_CLK, 11= SPI_SELECT, 12= IOREF

CARE SHOULD BE TAKEN TO MAKE SURE THAT PIN 1 ON THE BOARD AND THE CONNECTORS MATCH WHEN CONNECTING A NEW XP BOARD.

each Expansion connector has a set of 6 Solder Jumpers to are marked A and two are marked B and the remaining two are marked C. The idea is to select one of the following options and short the jumpers to enable the selected option you must also open the other solder Jumpers.

The options are:
C= Default I2c Buss using 3.3 Volt levels and with a 10K pull-up resistor on both lines to 3.3V.
B= I2C Buss using 5.5 Volt levels and and with a 10K pull-up resistor on both lines to 5.5V.
A= RXn,TXn    where n is the same number as the XP option connectors. (On the UNO and LEO versions of the board RX0,TX0 goes only to XP2. XP1 and XP3 can be used for I2C dunctions only.)

I2C on each XP connector can be selected at 3.3V or 5.5V and the three XP option boards do not need to be using the same levels. the Translation of these signals will be done on the BOT-LOGIC board and then passed to the arduino. the Level Translation is compatible with the full I2C bandwidth. 

PINS 4 and 5 can have different function