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Using Firmata board with mraa {#firmata}

Mraa can use a Firmata board as a subplatform. This means one can access the native IO as well as the IO on a firmata compatible board

Supported Firmata boards

  • Genuino/Arduino 101 running either CustomFirmata or StandardFirmata
  • Other Arduino boards will likely work but are as of yet unsuported

Using the subplatform API

Using the subplatform API is relatively simple, simply add '512', the platform offset to any IO calls. I2c 0 becomes I2c 512+0 etc... The API works from UPM or mraa in any of the bindings as long as you compiled mraa with -DFIRMATA=ON. Currently -DFIRMATA is not compatible with USBPLAT. Multiple subplatforms are not yet supported

Sending custom SYSSEX messages

You can use the firmata API to send custom SYSEX messages.

CurieImu Plugin

Using Customisable firmata we're able to use the onboard IMU to get data. This uses the public SYSEX firmata API from mraa and there is a UPM module that exposes this capability in a simple way. To use it your board needs to use CustomFirmata with the CurieIMU plugin

Limitations

Only one instance of mraa (one process linking to mraa) can communicate to an firmata subplatform. This is a limitation due to only having one application using the Uart at once. In order to get around this a daemon type methodology has to be used. Technically you can mirror the TTY port from firmata but this is likely going to cause issues