Follow up I2S 32bit word errors

[Josh Grob]

Hello Nordic staff (or anyone in the know),

I saw this post from @newtom almost a year ago which concluded that I2S master library does not support 32bit words from mics like the Knowles SPH0645. Is there any update or work around (not using I2S slave mode) since then? Thank you for the time and help.

Josh

[Jørn]

Hello Josh Grob

Unfortunately we do not have any work-around or update on this at the time being, and the conclusion in the post you link to is still valid today.

Best regards

Jørn Frøysa

[Josh Grob]

Thank you for the follow up and confirmation. If it helps influence prioritization for the next release I am very keen on seeing this fixed. It is definitely limiting the type of microphones I desire to use for my applications. Thank you

[Greg Tomasch]

Hello All,

I think there is a work-around of sorts now... Like everyone else, I was attempting to collect audio data from a modern 24-bit I2S MEMS microphone and ran into the hard-coded limitation of 48 SCK pulses per stereo I2S frame in I2S master mode. It dawned on me that there really is precious little difference between I2S master and slave modes... Except where the LRCK and SCK pulses come from.

My solution was to augment the PWM library to set the PWM carrier period directly in 16MHz ticks, not milliseconds. So I use two PWM channels; one to generate SCK and the other to generate LRCK and connect the PWM outputs to the I2S SCK and LRCK pins. I set the LRCK PWM channel period to be 64X that of the SCK PWM chanel period. I have a functioning peripheral application for SDK 13.0.0 and the pca10040 DK board located here:

github.com/.../master

I was using the Invensense ICS43432 microphone. There is a sample ".wav" audio file that demonstrates typical audio quality....

This may be considered as an ugly work-around but it doesn't require any other external devices to generate the clock signals...

Best Regards, Greg Tomasch