Now to the fun part, the cellular module. THere's a few pins that are used to control
the module. It uses SoftwareSerial to communicate with the microcoller
#8 - used as the FONA TXD (data out from module to AVR). This pin is not
exposed on the Feather
#9 - used as the FONA RXD (data out from AVR to module)
#7 - used as the FONA RI (ring interrupt) pin, you can use this to alert you when
an SMS or phone call comes in. Note that this is interrupt #4 (but on pin #7). This
pin is not exposed on the Feather
#4 - used as the FONA Reset pin. You can pulse this pin low to reset the FONA,
handy when starting up. This pin is not exposed on the Feather
Optional pins:
#5 - This pin is available on the breakout and is also connected to the FONA's
DTR pin if you want to use it for powersaving functionality, which is not enabled
by default
#6 - This pin is available on the breakout and is connected to FONA RTS in case
you want to use flow control, which is not enabled by default
Other Pins!
RST - this is the Reset pin, tie to ground to manually reset the AVR, as well as
launch the bootloader manually
ARef - the analog reference pin. Normally the reference voltage is the same as
the chip logic voltage (3.3V) but if you need an alternative analog reference,
connect it to this pin and select the external AREF in your firmware. Can't go
higher than 3.3V!
Key - this is by default tied to ground, cut the trace on the bottom and wire to a
microcontroller pin to manually turn the module on and off. (Pulse low for a few
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©Adafruit Industries
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