SIM900 Microphone Issue

[sreeram25]

Hi,

I connected PWM output (VOUT1 and VOUT2) pins of aP8942A (pre recorded voice) to SIM900 MIC pins via filter circuit.

When I first power on the board and make a call to SIM900 I am not able to listen the voice.

After that if I power OFF and ON the module, I am able to listen the voice.

Reset by using PWRKEY,NRESET is also not helping. Microphone works only after I power off and on module.

To again re-produce the issue, I had to power off the board for 15 mins and then power on.

Regards,
Sreeram

 

[BradtheRad]

There's a chance your source device is sending a glitch to the receiving device, causing it to malfunction.

A likely type of glitch would be a negative spike, or else a positive spike which is greater than the supply V.