Lots of SBCs out there are NOT bus 1 for the default I2C bus.
Can I suggest changing:

def __init__(self):
    # Initialize AHT20
    self.cmd_soft_reset()

to

def __init__(self, I2CBusNum=1):
    # Initialize AHT20
    self.I2CBusNum = I2CBusNum
    self.cmd_soft_reset()

and all SMBus(1) to SMBus(self.I2CBusNum) ?
That should maintain backwards compatibility for anyone using this module and flexibility for people using boards like the Rock Pi 4

Hi !

I try to write some python code for reading the AHT25 sensor.
The sensor is nothing special - only a humidity / temp sensor.

It´s connected to the Pi 4 directly with 15cm of wire cable to the I2C port of the Pi (Pin 3, 5).

If I use i2cdetect I can see the sensor:

pi@Pi4Test:~/python_sensor_aht20 $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- 38 -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Using i2ctransfer works also with no problems:

pi@Pi4Test:~/python_sensor_aht20 $ i2ctransfer -y 1 w3@0x38 0xac 0x33 0x00 r6
0x98 0x74 0xeb 0x35 0xe4 0x92

And if I decode the resulting bytes I get plausible readings. I even can see that the temp rises when I touch the sensor.

Now I tried to read the sensor with your python lib but without any luck ...
I always got errors like this:

    i2cBus.write_i2c_block_data(AHT20_I2CADDR, 0x0, AHT20_CMD_SOFTRESET)
  File "/home/pi/messy/.virtualenvs/Source/lib/python3.11/site-packages/smbus2/smbus2.py", line 643, in write_i2c_block_data
    ioctl(self.fd, I2C_SMBUS, msg)
OSError: [Errno 121] Remote I/O error

Sometime I see Error 5, too (Input Output error)

I tried pullups with 2k2, 4k7 and 10k. But nothing seems to help.

Do you have any idea what can cause this errors? It´s frustrating ... All other sensors I try work like a charm. But this sensor drives me crazy :-)

Hope on any hint.

Dominik

Hello,

This looks like an awesome Python module to go along with the AHT20. Thanks for your work on this!

It looks like you are using hex values in the AHT20.py to define the pins on the Pi that the sensor is connected to.

Would it be possible to provide a pinout or picture of which pin is connected where?

That would be very helpful!

Thank you,
Cody Hill