Grove I2C TB6612 Motor Driver source code

Is the source code for the microcontroller firmware on the Grove TB6612 Motor Driver available for examination some place?

I am working on a stepper motor device driver for Ada on Linux, and seeing some discrepancies between what is in the Arduino library and the actual behavior of the board I have. I would like to figure out what is going on by looking at the firmware source code.

Among other things, I can’t get the board to drive full steps, and STANDBY and NOT_STANDBY appear to be reversed.