基于Standard Firmata，C# SerialPort.Write()调用Arduino触发的Firmata函数咨询

Hey there! I’ve spent plenty of time tinkering with Standard Firmata and Arduino serial communication, so let me break this down clearly for you.

First off, Standard Firmata doesn’t trigger random custom Arduino functions you might have written—instead, it processes incoming serial data through its own built-in library logic, which runs in the Arduino’s loop() function. Here’s exactly what happens:

• Core Entry Point: Every byte you send via SerialPort.Write() gets picked up by the Arduino’s serial buffer. The Firmata library’s loop() code repeatedly calls Firmata.processInput(), which reads from this buffer and starts parsing the data.
• Protocol-Driven Function Triggers: What specific Firmata function runs next depends entirely on the format of the data you send (you need to follow the Standard Firmata protocol for this to work):
  • If you send a digital pin write command (e.g., setting pin 13 HIGH), Firmata.processInput() will parse the message and call handleDigitalMessage(), which ultimately executes digitalWrite() on the target pin.
  • For analog pin write commands (like PWM output), it will trigger handleAnalogMessage(), which calls analogWrite().
  • If you send a SysEx (System Exclusive) message (used for custom or extended commands), it will invoke handleSysexMessage(). You can even register your own custom callback for SysEx messages using Firmata.attachSysexCallback() if you need to add custom behavior.
• Invalid/Non-Protocol Data: If you send raw bytes that don’t match the Standard Firmata protocol structure, Firmata.processInput() will likely ignore them or skip over unrecognized bytes—no specific function will trigger in that case.

A quick example: If you construct the correct Firmata frame to set digital pin 13 HIGH and send it via SerialPort.Write(), the Arduino’s Firmata library will:

1. Read the bytes in loop() via Firmata.processInput()
2. Recognize it as a digital message
3. Run handleDigitalMessage() to execute the pin state change

内容的提问来源于stack exchange，提问作者TIsConfused