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Topic: Workaround for missing I2S transmit connection on SARA-U201 (Read 252 times) previous topic - next topic


I have several questions regarding a workaround for the missing transmit connection on the MKR board.

I am working on a security device that can listen to the surroundings and alarm via SMS text if sound levels exceed preset limits. The SMS recipient is notified of course with preprogrammed messages. I then start a timer and if the alarm is not acknowledged within a preset time limit then another text is sent. This continues until another preset limit is reached at which time I wanted to place a voice call and, if answered, gate the speaker through to the caller so they could hear what was causing the alarm. I thought at first to simply identify the pin on the SARA-U201 chip and make a connection to it myself. If later revisions of the board include this feature then I could eliminate the modification at that time.
The other idea I had was to make a recording of the disturbance and store it on an SD card as a WAV file. Then when the call is connected I could send the WAV file through. This serves dual purposes in that the disturbance might not be there anymore when the timers finally call for the voice system to be activated and so the actual sounds that caused the system to trip are preserved. It also creates a physical record for forensic analysis at some point in the future.
So here are my requests:
1) If there are any references to the procedure for creating a WAV file from a microphone board attached to the system I would appreciate a link.
2) If there are references to the process for sending a WAV file through I would also appreciate a link.
3) Would it be feasible to make the connection to the SARA-U201 I2C transmit line and approach it from that perspective?

Thanks for your attention and/or help.


I am replying to my own post.
A previous poster claimed voice calls via the MKR GSM were impossible due to a missing connection to the SARA-U201 TX terminal.  This is not correct.  If it were correct then why would the MKRGSM library GSM Voice Call Class have two functions named enableI2SInput() and disableI2SInput() ?  Simply stated, it would not.  I am now looking for an I2S based microphone to either take the place of my microphone attached to an analog input or merely support the voice call function.
For the poster asking how to use the GSM 1400 to make voice calls I suggest you use the sound and I2S libraries to figure it out.  That is what I plan to do.
I will probably post some code snippets showing how I did it.  That is, once I do it. :-)


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