adafruit_i2c_device_micropython

Modifications:

I2CDevice().readinto()

• In that method you will find the following code:

x = buf[start:end]
self.i2c.readfrom_into(self.device_address, x)
buf[start:end] = x

• It might look strange
• But
• CircuitPython has their own C code that writes into the buffer in place, while slicing the buffer in python makes a copy
• When we simply passed buf[start:end] into readfrom_into, not realizing it made a copy, the adafruit library we were using (TODO add link to code) was hanging in a loop
• It seems like that was because the CircuitPython C code was writing into the buffer asynchronously while the main python code waited for the write to happen to buf, which never did
• So we slice the buf and store the new buf in a variable, then we pass that variable into readfrom_into (now the newly written data is in x), and then we write that into the original buf variable
• Also, using the other MicroPython I2C functions were giving us a not implemented for I2C device error (didn't investigate why further)
• Essentially self.i2c.readfrom_into(self.device_address, buf[start:end]) doesn't work because buf[start:end] makes a copy of buf, but we want to write to buf in place