I built a setup with a WP7607 mounted on a mangOH green board and a µC to send and receive audio data using the PCM WP7607 interface.
The µC acts as Master and the WP7607 as slave. To match the required voltage level of the slave, a level shifter is used to shift down the signal of the master from 3.3 V to 1.8 V. Another level shifter shift the level of the PCM_OUT signal up.
With this configuration, the PCM_OUT pin from the WP7607 sends correctly the data to the µC. However, as soon as I connect the PCM_IN signal between the mangOH board and the level shifter, the voltage drops to 300 mV. Consequently, a signal can’t be correctly transmitted between the µC and the WP7607, and, after establishing a call, the modem doesn’t produce any audible signal. The other signals (PCM_SYNC and PCM_CLK) keep their level (1.8 V) without any voltage drop.
To setup the PCM interface I used the following commands
Is there any other related command to correctly setup the interface?