Window Shopping Firmata: Connect Microcontrollers To Computers

Reading about LabVIEW LINX stirred up memory of something with a similar premise. I had forgotten its name and it took a bit of research to re-discover Firmata. Like LINX, Firmata is a protocol for communicating between microcontrollers and desktop computers. Like LINX, there are a few prebuilt implementations available for direct download, such as their standard Arduino implementation of Firmata.

There’s one aspect of the Firmata protocol I found interesting: its relationship to MIDI messages. I had originally thought it was merely inspired by MIDI messages, but the Firmata protocol documentation says it is actually a proper subset of MIDI. This means Firmata messages have to option to coexist with MIDI messages on the same channel, conveying data that is mysterious to MIDI instruments but well-formed to not cause problems. This was an interesting assertion, even with the disclaimer that in practice Firmata typically runs at a higher serial speed on its own bus.

Like LINX, Firmata is intended to be easily implemented by simple hardware. The standard Arduino implementation can be customized for specific projects, and anything else that can communicate over a serial port is a candidate hardware endpoint for Firmata.

But on the computer side, Firmata is very much unlike LINX in its wide range of potential software interfaces. LINX is a part of LabVIEW, and that’s the end of the LINX story. Firmata can be implemented by anything that can communicate over a serial port, which should cover almost anything.

Firmata’s own Github hosts some Python sample code, and it is but one of five options for Python client libraries listed on the protocol web site and they carry along some useful tips like using Python’s ord()/chr() to convert hexadecimal data to/from Firmata packets. Beyond Python, every programming language I know of are invited to the Firmata party: Processing, Ruby, JavaScript, etc.

Since I had been playing with C# and .NET recently, I took a quick glance at their section of Firmata. These are older than UWP and use older non-async APIs. The first one on the list used System.IO.Ports.SerialPort, and needed some workaround for Mono. The second one isn’t even C#: It’s aimed at Visual Basic. I haven’t looked at the third one on the list.

If I wanted to write an UWP application that controls hardware via Firmata, writing a client library with the newer async Windows.Devices.SerialCommunication.SerialDevice API might be a fun project.

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