BITMAIN APW9 power supply

[tolyan249]

There is a BITMAIN APW9 power supply, and I don't know if anyone has worked with it. It regulates the voltage using i2c, and I can't even scan its address because the 9th SDA pulse is always 0. As a result, the ACK always comes. If I remove the connector from the power supply, the 9th SDA pulse becomes a perfect 1.

[Stephen Moss]

I may help people to resolve your problem if you could supply a link to/data for the I2C protocol, and the code you are using. Without that it would be difficult to see what you may be doing wrong.
After a quick search the only reference I could find was...

The 4-PIN signal connector is the interface between the external control board and the power supply. The SDA/SCL is an I2C bus. The output voltage of the power supply can be adjusted through I2C. EN is the ENABLE signal of the power supply. The control board can enable the power supply through EN, active high.

From that my guess would be that perhaps you have to set the EN pin high to disable the PSU (no output/enable comms?) while you are communicating with it and then set it low to accept and either output the new voltage following correct communications, or the previous voltage if the instructions received were rejected.
But with so little information to go in I may be wrong.