Logic pins
This is the general purpose I/O pin set for the microcontroller. All logic is 3.3V
#0 / RX - GPIO #0, also receive (input) pin for Serial1 and Interrupt #2
#1 / TX - GPIO #1, also transmit (output) pin for Serial1 and Interrupt #3
#2 / SDA - GPIO #2, also the I2C (Wire) data pin. There's no pull up on this pin
by default so when using with I2C, you may need a 2.2K-10K pullup. Also
Interrupt #1
#3 / SCL - GPIO #3, also the I2C (Wire) clock pin. There's no pull up on this pin
by default so when using with I2C, you may need a 2.2K-10K pullup. Can also do
PWM output and act as Interrupt #0.
#5 - GPIO #5, can also do PWM output. Also connected to the FONA's DTR pin if
you want to use it for powersaving functionality, which is not enabled by default
#6 - GPIO #6, can also do PWM output and analog input A7. Also connected to
FONA RTS in case you want to use flow control, which is not enabled by default
#9 - GPIO #9, connected to FONA RXD.
#10 - GPIO #10, also analog input A10 and can do PWM output.
#11 - GPIO #11, can do PWM output.
#12 - GPIO #12, also analog input A11 and can do PWM output.
#13 - GPIO #13, can do PWM output and is connected to the red LED next to the
USB jack
A0 thru A5 - These are each analog input as well as digital I/O pins.
SCK/MOSI/MISO - These are the hardware SPI pins. Also used to reprogram the
chip with an AVR programmer if you need.
Cellular Module
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