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adafruit / Adafruit_CircuitPython_SGP40

CircuitPython library for the Adafruit SGP40 Air Quality Sensor
MIT License
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Reset not working with Blinka MCP2221 #7

Closed caternuson closed 3 years ago

caternuson commented 3 years ago

Re this thread: https://forums.adafruit.com/viewtopic.php?f=19&t=182647

Tested locally with an MCP2221 and SGP40 connected via STEMMA QT cable.

(blinka) hellokitty@bench:~$ python3
Python 3.8.10 (default, Jun  2 2021, 10:49:15) 
[GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import board
>>> import adafruit_sgp40
>>> sgp = adafruit_sgp40.SGP40(board.I2C())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_sgp40.py", line 115, in __init__
    self.initialize()
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_sgp40.py", line 144, in initialize
    self._reset()
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_sgp40.py", line 152, in _reset
    self._read_word_from_command(delay_ms=50)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_sgp40.py", line 243, in _read_word_from_command
    i2c.write(self._command_buffer)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_bus_device/i2c_device.py", line 84, in write
    self.i2c.writeto(self.device_address, buf, start=start, end=end)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/busio.py", line 157, in writeto
    return self._i2c.writeto(address, memoryview(buffer)[start:end], stop=stop)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_blinka/microcontroller/mcp2221/i2c.py", line 19, in writeto
    self._mcp2221.i2c_writeto(address, buffer, start=start, end=end)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_blinka/microcontroller/mcp2221/mcp2221.py", line 315, in i2c_writeto
    self._i2c_write(0x90, address, buffer, start, end)
  File "/home/hellokitty/blinka/lib/python3.8/site-packages/adafruit_blinka/microcontroller/mcp2221/mcp2221.py", line 233, in _i2c_write
    raise RuntimeError("I2C slave address was NACK'd")
RuntimeError: I2C slave address was NACK'd
>>>

The _reset func looks a bit hack-ish, like it expects some kind of exception to be thrown. And for MCP2221, this ends up being a different exception. Otherwise, traffic looks nominally the same for MCP2221 and a QtPy running native CP.

QTPY image

MCP2221 image

caternuson commented 3 years ago

Hopefully fixed with #8