I am trying to communicate with a bq27510EVM from a target board that is powered with 3.3V. The bq27510EVM has no problem communicating with the bqEasy software that accompanies the EVM. However, when the bq27510EVM is connected to the target board (and no longer connected to the desktop running bqEasy), the bq27510 fails to respond with an ACK upon receiving the slave address. I have removed the pullup resistors from the EVM board since the target board already has pullup resistors. However, the I2C signals are pulled up to 3.3V instead of 2.5V. This is the only difference I can see in the two different setups. Is the bq27510 unable to communicate with a higher pullup voltage? I have included two images that show the scope output of the communication from the desktop running bqEasy and from the target board.
The first image below shows the successful communication from the desktop to the 27510EVM.
The second image below shows the failed communication from the target board to the 27510EVM.
Thanks,
Elizabeth