Firmware for the ATTNode v3
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ATTNode v3 Firmware

This is the code repository for ATTNode v3 compatible firmware. At the moment it supports LoRa communication using OTAA and a growing number of sensor, like the BME280 and SHT21 for temperature, humidity and atmospheric pressure, MH-Z19C and SCD30 for CO2 or HM330x for Particulate Matter. It also uses deep sleep to save energy between Measurements.

The firmware is developed using PlatformIO. At least version 5.1.0 is needed for ATTiny3216 support.


The full documentation for firmware options, payload decoders and programming can be found at

Configuration and Programming

To set the fuses for clock speed, BOD levels etc., use the "Set Fuses" operation in PlatformIO. This has to be done once for a "fresh" Node or when the Board Config in platformio.ini was changed. Afterwards it is enough to use the normal "Upload" function for Code or config.h changes.

Before programming a node, copy src/config.h.example to src/config.h and set the used sensor, LoRaWAN keys and other options as needed.

Programming is done using a MicroUPDI Programmer, settings in platformio.ini are set to use it. For other pogrammer options see the PlatformIO Documentation


The firmware has the ability to produce some debug output via the Serial UART as long as there is no sensor using the UART. To enable it, uncomment the line -D DEBUG in platformio.ini. This will produce some debug output showing the state of the node. The following macros are available as a replacement for the normal Serial.print and Serial.println functions:

DEBUG_PRINT("Debug Output");
DEBUG_PRINTLN("Debug Output with Linebreak");

These will only produce additional code in the firmware when the DEBUG-Flag is enabled, and will be entirely removed in the ouput binary if not. The macros work like the normal Serial.print* statements form the standard arduino functions.

Payload Decoder

You need to specify a Payload Decoder fitting for your configured Sensors for a Node. See payload/index.html in this repository. Open it in your Browser of Choice and select the enabled sensors. It will generate the Payload Decoder fitting for the choosen Sensors. You can also use the Online Version at

It is possible to change the sending interval via Downlink-Packets at runtime. Downlinks for setting the transmit interval have to be sent on port 1. The time between Transmits is specified in minutes (or more exactly, 64 Second intervals) and as a 2 byte value, which will be interpreted as an uint. So for example 0x0001 means 1 Minute, 0x0002 means 2 Minutes and so on. Sending 0xFFFF resets the value to the compiled in default.

Sending an arbitrary value on port 2 will activate the calibration sequence for sensors that support it (like some of the CO2-Sensors).


Parts of this code where kindly provided by @shempe