I use I2C to read UCD90120A, but the CLK pulls down about 34ms during the transmission.
Should I adjust some settings about UCD9020A?
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UCD90120A is a PMBus-Centric device and follow the PMBus protocol.
if the host's transaction does not follow PMBUs protocol, there could be a issue.
For example: if host sends the following :
START BIT + (DEVICE_ADDRES + Wbit) + STOP
This kind of protocol is not supported by UCD.
I believe that's how I2C detect works to scan the address on the bus.
Thanks, I check the detect waveform just like you said.
I had another two questions about stretching > if clock stretching happened can we use i2cget command to get the waveform?
the other question is when we use a logic analyzer to check the waveform, the clock stretching happened, should we do something on our host device?
and after timeout is 0xff normal condition?
Yes, your understand is right.
if you use the i2Cread as the following, device will not respond since this is not a pmbus protocol.
START BIT+ ADDRESS+Rbit
The read shall always start with Write first then repeat start to get the data.