Thanks a lot tomdv !
This greatly helped me to get my QDY30A working.
I used a cheap RS485-to-USBserial adapter:
https://www.amazon.de/dp/B0BV7DVKR5?ref=ppx_yo2ov_dt_b_product_details&th=1
and the great open source tool:
https://pymodbus.readthedocs.io/en/latest/source/repl.html
After installation with:
pip3 install “git+https://github.com/pymodbus-dev/repl”
started with: pymodbus.console serial --port /dev/cu.usbserial-A50285BI --baudrate 9600 --bytesize 8
Then within the running console:
client.read_holding_registers address=0 count=7 slave=1
which delivered:
{
“registers”: [
1,
3,
1,
1,
629,
0,
2000
]
}
which delivers correct pressure readings.
However the sensor reported some minor false infos:
Pressure unit as “1 = cmH2O”, but in fact uses “2 = mmH2O”
Decimal places as “1 = ###.#” but in fact uses “0 = ####”
Eventually realized to integrate in ESPhome for use in HomeAssistant:
Water level sensor QDY30A modbus RS485 with ESP32 S2 mini