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Forum Index : Microcontroller and PC projects : CMM2 - audio not working

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x4nd
Newbie

Joined: 05/07/2020
Location: United Kingdom
Posts: 11
Posted: 11:40am 23 Aug 2020
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Hi,

First-time poster here; I have searched the forum looking for a previous question but didn't see one covering my exact problem.

We can't get any sound out of our CMM2.  We have populated the board ourselves (my son did the soldering while I checked his work).  It's the version with plug-in Waveshare and resistor-packs (PCB v3.0).

Everything else seems to work fine - board flashed, boots, we can use the SD Card and run/save programs and the board keeps time, etc.  All great except it's mute.

I confess that we plugged in headphones initially because we didn't read the section in the manual about the 3.5mm jack being a line out.  But since then plugged into speakers and still nothing.

The audio jack looks like it's soldered in OK.

Is there anything we could have done wrong with the board jumpers, software, etc.? Is there anything we can check on the board to fault-find?

Any help greatly appreciated.

-Stuart
If only there were more hours in the day..
 
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10580
Posted: 12:00pm 23 Aug 2020
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When the firmware is running you should see a voltage of approximately 1.65V on pins PA4 and PA5 on the Waveshare. Then use the command DAC 1,0 and PA4 should drop to 0V
DAC 1,3.3 and it should go to 3.3V. Use DAC 2,voltage to test PA5
 
x4nd
Newbie

Joined: 05/07/2020
Location: United Kingdom
Posts: 11
Posted: 03:07pm 23 Aug 2020
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Thanks for your quick reply.

I have tested PA4 and PA5 both in and out of the maximite board and I get 0v on both pins.  The DAC command seems to do nothing for either pin.  Do I need to set the waveshare board jumpers at all?  I have no jumpers on there and the two switches set to FLASH and 5VIN.

I have buzzed the PA4 and PA5 pins and found the PA4 is connected to the tip of the audio jack OK and the PA5 pin is connected to both pins near the front of the 3.5mm connector (the side next to the 40-pin connector).  So I assume the CMM board is OK, but there is a problem with the firmware/waveshare?
If only there were more hours in the day..
 
matherp
Guru

Joined: 11/12/2012
Location: United Kingdom
Posts: 10580
Posted: 03:09pm 23 Aug 2020
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Install the VREF link on the waveshare and try again. If this works and I suspect it will then you are missing the resistor on the motherboard that supplies VRef or it is the wrong value
Edited 2020-08-24 01:10 by matherp
 
x4nd
Newbie

Joined: 05/07/2020
Location: United Kingdom
Posts: 11
Posted: 06:11pm 23 Aug 2020
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THAT'S IT!

Thankyou so much Peter!

I'll go and check the resistors now.  I also notice that the video signal is a little more stable (did have some small glitches).

Son is happily playing Wolfenstein with audio! :)
If only there were more hours in the day..
 
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