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Topic: GSM Noise Problem in Voice Calls (Read 1 time) previous topic - next topic

tmkeng

Has anyone had any luck using a GSM shield and Arudino to make voice calls?  I am having no problem with SMS messages or establishing voice calls.  However voice calls have severe audio buzzing interference that makes the voice unintelligible.  I can hear the voice under the noise so i know the connection is working.  I have read in numerous places that you can simply add a headset and/or speaker and microphone to the audio jacks on the GSM shield, but not much info on how to eliminate the GSM noise.  It is obviously coming from stray RF pickup in the audio circuits. I've tried shielding the speaker and microphone wiring and adding the RF bypass caps suggested in the board's application notes, but that didn't help.  I've even tried making voice calls without any speaker or microphone connected and still hear the loud buzzing (on the calling phone), indicating the pickup is on the GSM shield itself and not in the (non-existent) external microphone/speaker wiring.  I have used a couple of different GSM shields from different manufacturers with the same result (e.g. Geeetech and Itead).  I am about to give up on including voice call capability in my project because nothing seems to make it go away.  So I'm hoping someone out there in Arduino land can offer some advice.  I am interested primarily in advice from someone who has actually done this successfully rather than speculation on what "might" work, however all suggestions are most welcome.

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