Datasheet

This is the general purpose I/O pin set for the microcontroller.

All logic is 3.3V

Nearly all pins can do PWM output

All pins can be interrupt inputs

#0 / RX - GPIO #0, also receive (input) pin for Serial1 (hardware UART), also can be analog input

#1 / TX - GPIO #1, also transmit (output) pin for Serial1, also can be analog input

#20 / SDA - GPIO #20, 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.

#21 / SCL - GPIO #21, 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.

#5 - GPIO #5

#6 - GPIO #6

#9 - GPIO #9, also analog input A7. This analog input is connected to a voltage divider for the lipoly battery so

be aware that this pin naturally 'sits' at around 2VDC due to the resistor divider

#10 - GPIO #10

#11 - GPIO #11

#12 - GPIO #12

#13 - GPIO #13 and is connected to the red LED next to the USB jack

A0 - This pin is analog

input

A0 but is also an analog

output

due to having a DAC (digital-to-analog converter).

You can set the raw voltage to anything from 0 to 3.3V, unlike PWM outputs this is a true analog output

A1 thru A5 - These are each analog input as well as digital I/O pins.

SCK/MOSI/MISO (GPIO 24/23/22)- These are the hardware SPI pins, you can use them as everyday GPIO pins

(but recommend keeping them free as they are best used for hardware SPI connections for high speed.

RFM/SemTech Radio Module