I/O Connections

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Primary Cell Connections

USB Connector

A USB micro-B cable must be connected between this connector and a USB power source to provide power to the board.


When the USB Disable jumper is installed (factory default), this connector is for power only. If the USB Disable jumper is removed, then the Development Kit will appear to the host computer as a Silicon Labs CP210x USB-to-serial converter, connected to serial port SerialA on the Cell.


Reset Button

Press to reset the Cell.


SD Change Button

Connected to the SD CHG pin of the Cell; functionality determined by the Cell.

I/O Device Connections

RS-232 Connector

When both the USB Disable and RS-232 Enable jumpers are installed, this connector provides RS-232 signaling levels to serial port SerialA on the Cell.


This is a male connector with "DTE" pinout, the same as you would find on a computer or USB-to-serial converter. As such, it can be directly connected to serial devices that have a female serial connector intended to connect to a computer.


Button A3 and Button A4

These buttons apply a low logic level to the corresponding Cell pin when pressed. If using these buttons, the Cell pin should be set for input with pull-up. These buttons will not interfere with alternate uses of the Cell pins as long as they are not pressed.


LED A5 and LED A6

These LEDs will light when the corresponding Cell pin outputs a low level and the corresponding jumper is in place.



The potentiometer allows a variable voltage to be applied to Cell pin A0 when the Pot - A0 jumper is in place. The voltage from the potentiometer can be varied over the approximate range 0 - 2.5V, depending on resistor tolerance and supply voltage variations. The Cell analog reference input Aref is connected to the high side of the potentiometer, so the 100% setting will always correspond exactly to the max ADC value if the Aref pin is selected as the analog reference voltage.


LM73 Temperature Sensor

This temperature sensor is connected to the I2C port on the Cell.


Digi XBee Radio Module Location

These pads provide a place to connect a Digi XBee radio module. The connections provide power and serial I/O connected to serial port SerialB on the Cell.