Deadlock when connected i2c device fails. #8
Description
I've connected some Adafruit SHT31-D Temperature & Humidity Sensors to the TCA9548A but once in a while one of the sensors fails to read properly with a remote I/O error. This is probably caused by the long wiring but in my application it's not a big deal as the program just tries again.
At least that was the case before I used the TCA9548A with just 2 sensors on the i2c of my Raspberry Pi. As the reading was done in a try: / except: the program continued to run. The remote I/O error didn't cause the i2c bus to hang so most of the time the next reading was succesful.
But when using the TCA9548A it's causing a deadlock on this error:
Traceback (most recent call last):
File "/home/pi/MainProgram.py", line 332, in ReadTempValue
TemperatureValue = '{0:4.1f}'.format(THsensor.temperature)
File "/usr/local/lib/python3.5/dist-packages/adafruit_sht31d.py", line 120, in temperature
raw_temperature, _ = self._data()
File "/usr/local/lib/python3.5/dist-packages/adafruit_sht31d.py", line 109, in _data
i2c.readinto(data)
File "/usr/local/lib/python3.5/dist-packages/adafruit_bus_device/i2c_device.py", line 97, in readinto
self.i2c.readfrom_into(self.device_address, buf, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/adafruit_tca9548a.py", line 76, in readfrom_into
return self.tca.i2c.readfrom_into(address, buffer, **kwargs)
File "/usr/local/lib/python3.5/dist-packages/busio.py", line 55, in readfrom_into
return self._i2c.readfrom_into(address, buffer, stop=stop)
File "/usr/local/lib/python3.5/dist-packages/adafruit_blinka/microcontroller/generic_linux/i2c.py", line 44, in readfrom_into
readin = self._i2c_bus.read_bytes(address, end-start)
File "/usr/local/lib/python3.5/dist-packages/Adafruit_PureIO/smbus.py", line 155, in read_bytes
return self._device.read(number)
OSError: [Errno 121] Remote I/O error
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/home/pi/MainProgram.py", line 336, in ReadTempValue
TemperatureValue = '{0:4.1f}'.format(THsensor.temperature)
File "/usr/local/lib/python3.5/dist-packages/adafruit_sht31d.py", line 120, in temperature
raw_temperature, _ = self._data()
File "/usr/local/lib/python3.5/dist-packages/adafruit_sht31d.py", line 106, in _data
self._command(SHT31_MEAS_HIGHREP)
File "/usr/local/lib/python3.5/dist-packages/adafruit_sht31d.py", line 100, in _command
with self.i2c_device as i2c:
File "/usr/local/lib/python3.5/dist-packages/adafruit_bus_device/i2c_device.py", line 175, in __enter__
while not self.i2c.try_lock():
File "/usr/local/lib/python3.5/dist-packages/adafruit_tca9548a.py", line 65, in try_lock
self.tca.i2c.writeto(self.tca.address, self.channel_switch)
File "/usr/local/lib/python3.5/dist-packages/busio.py", line 65, in writeto
return self._i2c.writeto(address, buffer, stop=stop)
File "/usr/local/lib/python3.5/dist-packages/adafruit_blinka/microcontroller/generic_linux/i2c.py", line 38, in writeto
self._i2c_bus.write_bytes(address, buffer[start:end])
File "/usr/local/lib/python3.5/dist-packages/Adafruit_PureIO/smbus.py", line 244, in write_bytes
self._device.write(buf)
OSError: [Errno 121] Remote I/O error
When I run a debug I see it's waiting for a lock on the i2c bus:
(gdb) py-list
54 """An object that must be locked to prevent collisions on a microcontroller resource."""
55 _locked = False
56
57 def try_lock(self):
58 """Attempt to grab the lock. Return True on success, False if the lock is already taken."""
>59 if self._locked:
60 return False
61 self._locked = True
62 return True
63
64 def unlock(self):
It seems the busio never releases the lock on the bus when running this setup and an error occures. But as it does without the TCA I assume there is some problem with the error handling in the TCA library.
Any ideas?