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Over UART

The serial port is the interactive way to use the driver: you type a command, the driver answers in text. It is the only way to calibrate, and the quickest way to try a setting. For real-time control of several motors use CAN.

The protocol

A command is #, a name, optionally a space and one number, and a line ending:

#P 16384
#P
#Cal
  • The name is case-sensitive and matches the firmware's spelling exactly (#Kpiq, not #kpiq); at most 19 characters, the number at most 19 characters, both together at most 20.
  • The line ends with LF (\n); a CR before it is accepted. Terminals send CR+LF when you press Enter, with the setting described in The serial terminal.
  • A Set/Get command with a number sets the value and prints it; without a number it only prints it. #P 16384 moves to position 16384 and prints the position; #P prints the position. One exception: #Openloop without a number starts the motor at the stored open-loop speed.
  • An action command takes no number: #Cal, #Save, #Idle.
  • A command the parser does not know is answered with Unknown command. So are the few names the parser accepts but has no handler for; the UART reference lists them.
  • 256000 baud, 8N1, 3.3 V.

The driver only answers

The driver never sends anything on its own, except with the cyclic commands: #Cyc 100 makes it print position, speed and Iq every 100 ms as $ <position> <speed> <Iq> (for BetterSerialPlotter), #Cyca 100 as Position:x,Speed:y,Iq:z (for the Arduino plotter); #Cyc or #Cyca without a number stops it.

Typical sessions

A first test after calibration:

#Ilim 1500        current limit for the motor
#V 16384          one revolution per second
#V 0
#P 0              back to the start
#Idle

Tuning:

#Kpv 0.02
#Kiv 0.001
#V 30000
#Save

Status:

#Info
#Error
#Temp
#Vbus

Every command is in the UART reference, grouped by what it does.

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