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Fona 3G audio problems
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Fona 3G audio problems

by jules999999 on Sun Jul 10, 2016 10:53 am

Hi. I have a Fona 3G connected to an Arduino Uno. With the Uno test program all functions seem to work (hardware tests, send and receive SMS etc.) except when I make or receive a voice call I have audio problems. When receiving a call, the “bell” sounds through the speaker but on pick up, there is no audio on the speaker (volume is set to 8). Also there is severe interference on the microphone. This seems to vary according to the physical position of the various components. Occasionally the interference can be eliminated and the microphone works and can be picked up on the other mobile making the call (but still no audio on the speaker!) The connections to the speaker and electret are no more than 60mm.
I have connected the (8 ohm) speaker and the electret (correctly polarised, pin connected to case to “-”) to the pins rather than the 3.5 jack. I have tried 3 different electrets and replaced the wiring with no change. (I have also tried an electret on the jack with no difference.) I have moved the Fona to widely different parts of the house in case there is a localised source of RFI but with no improvement.
I have attempted to make changes on the test program for external/internal connection but, of course, these don't apply to the 3G. (Incidentally, the connections given for the jack seem to imply that the microphone and speaker share a common ground but this is not true of the pin connections. Is this the case?)
I must be missing something, but what?

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Re: Fona 3G audio problems

by adafruit_support_rick on Mon Jul 11, 2016 9:47 am

What happens if you execute the 'e' command in FonaTest? Does that make the external audio come on?

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Re: Fona 3G audio problems

by jules999999 on Mon Jul 11, 2016 5:35 pm

Hi. Unfortunately, the "e" command just seems to throw up an error and the lack of sound from the Fona's speaker and the noise transmitted by the Fona remains the same. The curious thing is the way the noise alters as the components are moved around or even my hand moves around (a bit like a Theremin!) As I say, the leads to the microphone and speaker are short. The leads between the Fona and the Arduino are longer but not ridiculously so. All connections are by soldered header plugs and sockets. I haven't used a breadboard. I've examined all the connections under magnification. I am baffled! In these circumstances, there is sometimes a simple mistake which has been overlooked, but if there is one, I can't spot it!

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Re: Fona 3G audio problems

by adafruit_support_rick on Tue Jul 12, 2016 6:29 am

please post some pictures of your soldering and wiring

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Re: Fona 3G audio problems

by jules999999 on Wed Jul 13, 2016 6:13 am

Hi. Thanks for your continuing help! Here are three pictures of the soldering/wiring. You can see what I'm trying to achieve on my page at http://www.mr-r.co.uk/oldphone1.html.
Thanks again!
fona5.jpg
fona5.jpg (290.09 KiB) Viewed 480 times
fona4.jpg
fona4.jpg (359.64 KiB) Viewed 480 times
fona1.jpg
fona1.jpg (387.36 KiB) Viewed 480 times

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Re: Fona 3G audio problems

by adafruit_support_rick on Wed Jul 13, 2016 7:57 am

Gee. I don't know about those connectors. They're soldered on both sides?
What's odd is that the ringer works but not the call audio. That's why I was thinking that external audio wasn't enabled.
The mic interference that comes and goes by waving your hands sounds like a grounding issue. But you seem to have grounds in place.

And, why does the 'e' command in FonaTest give you an error? What error are you getting? Can you post the serial monitor trace?

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Re: Fona 3G audio problems

by jules999999 on Wed Jul 13, 2016 9:13 am

DSCF2018.JPG
DSCF2018.JPG (644.71 KiB) Viewed 473 times
Hi.
The "e" response is:
e
---> AT+CHFA=1
<--- ERROR
Failed
---> AT+CMIC=1,10
<--- ERROR
FONA>
Isn't this command only relevant to the 800 and 808? ("[e] set External audio (FONA800 & 808)" on the menu)
The connectors aren't anything fancy (or, hopefully, anything stupid) - just headers soldered to stripboard. The wires are only soldered on one side - they pass through a hole as strain relief. I've used them for years with no ill effects!
Thanks for your help!

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Re: Fona 3G audio problems

by adafruit_support_rick on Wed Jul 13, 2016 12:04 pm

Oops! You're right. The 'e' command is only for the 800 and 808

On the 3G, I think the command is AT+CSDVC=3
AT+CSDVC=1 goes back to the headphones.

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Re: Fona 3G audio problems

by jules999999 on Thu Jul 14, 2016 5:22 am

Hi. Thanks for your reply.
I'd just make the point that if I connect a microphone to the 3.5 jack connection (and keep the speaker on the external, I get the same noise on the remote phone (also if I disconnect the microphone completely, there is no noise). This seems to suggest in spite of any default settings, both external and internal microphone channels are open in some way. (Still no noise on the speaker except the ring tone.) The noise sounds digital to me, not audio hum.
Is it the case that the AT+CSDVC call is not built into the library? I notice there are three values: 1, handset, 3, external and 4, PCM. This is pulse code modulation?
I would be grateful for any further thoughts.

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Re: Fona 3G audio problems

by adafruit_support_rick on Thu Jul 14, 2016 9:10 am

jules999999 wrote:Is it the case that the AT+CSDVC call is not built into the library?

Yes, that's true. I'll see if I can try it out. If it works, I'll add it to the library.

Let's try a new Fona. Please email support@adafruit.com with a link to this thread for a replacement 3G

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Re: Fona 3G audio problems

by jules999999 on Thu Jul 14, 2016 10:43 am

Thanks for that!

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Re: Fona 3G audio problems

by jules999999 on Fri Jul 15, 2016 4:47 am

Hi
Unfortunately, the FONA 3G is out of stock at Adafruit and I can't find out when new stock is expected. Anyway, I have reached into my wallet and ordered another from our local suppliers in the UK, Pimoroni. I suppose at the end of the day, I will own two FONAs and I expect I can think up some other project to make use of the extra one!
I will let you know what happens with the new FONA.

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Re: Fona 3G audio problems

by adafruit_support_rick on Fri Jul 15, 2016 10:07 am

Let me know if the new one works for you.

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Re: Fona 3G audio problems

by jules999999 on Mon Jul 18, 2016 7:12 am

Unfortunately, neither Adafruit nor Pimoroni have FONAs in stock! However, after a bit of a struggle I managed to to get the driver for the USB AT port to install (I tried so many things, I'm not sure exactly how I did it - it would help if the drivers which are not needed were culled). I then sent AT+CSDVC=3,1 and lo and behold it worked!

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Re: Fona 3G audio problems

by jules999999 on Wed Jul 20, 2016 9:03 am

Hi
Although the AT command seemed to activate the external microphone and speaker, I was still getting audio noise. I tried reducing the length on the connecting leads but it didn't make any difference.
I then dredged up from deep memory something about this sort of antenna needing a ground plane. (I haven't tried the "stick-on" antenna as I can't get a signal with it in this house.) So I tested a piece of aluminium, insulated with gaffer tape as a ground plane. I also added a 100nF capacitor across the microphone leads. This made a big improvement although there is still a slight tendency to noise being apparent when the equipment is moved or an object (like myself) is moved round it. I'm still not really sure what's going on!
[img]
fona6.jpg
[/img]
[img]
fona7.jpg
[/img]
Attachments
fona7.jpg
FONA on ground plane
fona7.jpg (521.35 KiB) Viewed 392 times
fona6.jpg
FONA with shortened leads
fona6.jpg (415.64 KiB) Viewed 392 times

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Please be positive and constructive with your questions and comments.