Hi - I'm using PTN5150A in a USB peripheral. It's configured as a UFP.
The only function I need is to detect what current is advertised by the host, so I can determine how much I can pull from the USB port.
I'm using I2C to communicate with the device. The relevant bit of the schematic is shown below. R306 and R399 are 10K. There are appropriate pull-ups on the I2C bus. Supply voltage looks fine.
All I need to do is read from register x01 and register x04. I understand that individual byte write/reads are required. I can read register x01 but register x04 always returns 0.
I do do dummy write to register x01, followed by a single byte read. x0B is returned (as expected)
I then do a dummy write to register x04, followed by a single byte read. x00 is returned. In fact all the other registers seem to return x00.
I'm pretty familiar with I2C protocol, so I don't think I'm doing something stupid (but it's always possible of course!) Is there anything obvious to anyone else's eyes that I haven't considered?
Many thanks.
I see your test waveform which have glitch below picture green oval marked, can you eliminate this?
Waveforms attached...
I'm not sure which bit of the schematic would be helpful. Here's a bit more context. The big chip is an FTDI 4222H which is acting as I2C master. R304 and R305 are pull-ups, 4.7k each. C309 is 100nF, close to the chip. All the other slave chips on the board work fine, so I'm pretty certain there's nothing wrong with reading & writing to I2C slaves.
