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Can 1.536MHZ PDM clock generate 16kHz output sample rate

Posted: Thu Dec 15, 2016 4:25 am
by xyx361100238
Hi, all
According the Microphone array library V2.0.0 manual,feature 1&2:
1、48kHz, 24kHz, 16kHz, 12kHz and 8kHz output sample rate by default (3.072MHz PDM clock),
2、44.1kHz, 22.05kHz, 14.7kHz, 11.025kHz and 7.35kHz output sample rate by default (2.8224MHz PDM clock)
Is this means I cann't generate 16kHz sample rate output through 1.536MHZ(half of defualt) PDM clock?If it can be, how to modify src code.
THX!

Re: Can 1.536MHZ PDM clock generate 16kHz output sample rate

Posted: Thu Dec 15, 2016 10:43 am
by andrew
In order to set up the mic_array library for a 1.5MHz PDM clock and 16kHz output sample rate you need a total decimation factor of 32x3 = 96. This is not by default supported, however, if you read the advanced filter design section of the docs then it explains that you can generate any output decimation factor you desire. The script is currently being updated to make it easier to use but for now you should be able to achieve the result you want with:

python fir_design.py --add-third-stage 3 0.42 0.52 my_decimator

to generate a filter that will do a final stage divide by three. Hope this helps. Let me know if you have any problems as I tested it on 'not version 2.0.0'

Re: Can 1.536MHZ PDM clock generate 16kHz output sample rate

Posted: Mon Dec 19, 2016 3:55 am
by xyx361100238
THX,andrew
According to your cmd,I generate a filter divide by 3,and it works,thx a lot.