Sound crackle during boot with PCM5102 DAC

[omersiar]

Investigate if it can be silenced with software.

[soyersoyer]

PCM5102 DAC has an XSMT pin that might be good for this.

XSMT Pin (Soft Mute and Soft Un-Mute)

For external digital control of the PCM510x, the XSMT pin must be driven by an external digital host with a specific/minimum rise time (tr) and fall time (tf) for soft mute and soft un-mute. The PCM510x requires tr/tf times of less than 20ns. In the majority of applications, this shouldn’t be a problem, however, traces with high capacitance may have issues. When the XSMT pin is shifted from high to low (3.3V to 0V), a soft digital attenuation ramp is started. –1dB attenuation will be applied every 1tS from 0dBFS to –∞. This attenuation takes 104 sample times. When the XSMT pin is shifted from low to high (0V to 3.3V), a soft digital “un-mute” is started. 1dB gain steps are applied every tS from –∞ to 0dBFS. This ramp-up takes 104 sample times.

Currently, this is set to HI on the solder bridge 3 of the GY PCM5102 module, but (without the bridge) it could be set via pin 3 after boot. I haven't tried it, it's just an idea.

[soyersoyer]

https://github.com/probonopd/MiniDexed/pull/912