Colibri iMX7D 512MB WinCE analog audio ouput issue

Technical Support
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1

Hi Support Team,

We are testing analog output function of Colibri iMX7 under WEC7 V1.3b2, test condition is clicking volume bar of Start/Setting/Control Panel/Volume&Sound to play default system sound, meanwhile using oscilloscope probing pin-2 of C4 on Colibri Eva Board(Headphone-L output) to capture the sound waveform.

Then an interesting thing is found that when single click the volume bar with aournd 2s interval time, the output wave volume is significantly weaker than continiously clicking (for example, double click, but increase the trigger level to capture the second time clicking sound waveform), here below is some comparing captured waveform for reference.

1). WinCE default volume setting (volume bar on 60% position)

./ single click -

./ double click -

  1. WinCE biggest volume setting (volume bar on 100% position)

./ single click -

./ double click -

3). WinCE default volume setting (volume bar on 60% position), but with HPVolume registry key added to Audio driver registry with value 0.

./ single click -

./ double click -

4). WinCE biggest volume setting (volume bar on 100% position), but with HPVolume registry key added to Audio driver registry with value 0.

./ single click -

./ double click -

the backgroung for this testing is we will connect an amplifier to headphone_L pin to drive a speaker, and same time we have a resistive touch screen, when pressing touch screen, there is default system sound output, but when single pressing like above testing, the sound is very samll, then continiously pressing, the sound becomes too loud compareing the first pressing, this gives bad experience.

Thanks and Best Regards

Simon

2

Hi Simon,

I’m looking at the issue. i’m pretty sure that the problem you are seeing comes from a special feature in the Audio Coded (SGTL5000). It has a soft start ramp feature to reduce click/pop sounds when starting to play samples.
This can be disabled, but unfortunately the imX7 driver does not allow any customization of Codec Registers yet. I will add this feature (which we have on other SOCs already) and this will allow you to disable the Soft Ramp feature)

3

Hi @germano.tx ,

Thanks a lot for the reply, great to know the details of this issue and will waiting for your updating solution of the new BSP feature to disable the soft ramp.