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gcallipo / RadioDSP-Pico

Audio Filter DSP for Shorthwave Receiver. This Is a Digital Signal Processing to compute the audio of a Radio receiver. The project Is based on the Raspberry Pico pi board. The project implements some usefull filters and show how to setup a simple audio dsp realtime processing chain using ADC In and I2S Out.
Creative Commons Zero v1.0 Universal
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Migration to the Earlephilhower's Arduino core. #3

Closed nezumi-tech closed 1 year ago

nezumi-tech commented 1 year ago

The Earlephilhower's Arduino core is based on RPi Pico C/C++ SDK so it supports overclocking. https://github.com/earlephilhower/arduino-pico

To enable migration to the Earlephilhower's Arduino core, I added include hardware/pwm.h statement.

gcallipo commented 1 year ago

Moved to Earlephilhower's Arduino core.

gcallipo commented 1 year ago

Hi, I'm starting to think to the next test o perform in the next weekend. At the current sample rate ( 48 kHz ) we hame no more than 20 uSec to complete the filter chain eleboration, With the overclock you speedup the processor to perform the fir calculatuon fast but the 20 uSec remain a constant. Then we Need to operate in two directions : 1) increase the slot time to perform the filter elaboration , changing the sample rate from 48 to 24 kHz , this allow to increase the slot time to 41 uSec. 2) with a lower sample rate we can recalculate the filters with a decimation by 2 , the new sample rate decimated will be 12kHz , low samplerate = more filter efficency.

Another approach could be to use a fir calculatuon optimization.

For example : if I works with a fir with 100 taps and use a decimation factor by 4, I Will produce a sample output every 4 input samples , this mean that for 3 audio interrupt I don't performs elaboration. The idea Is to divide the elaboration of all 100 taps to each audio interrupt the I Will decrease the filter complexity by a factor of 4 . I think that this can helps to obtain the right bandwidt.

I Hope that this can help to understood the problem.

In the next weekend I Hope to have some spare time to mele the tests.

Bye. Giuseppe.

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