[GreenKeys] Minimal DSP TU Working!

[gil baudot.net]

Hi Harold:

That dsp-tu is a great idea, and looks like a fun bit of coding.  I am currently playing with an stm32f4 part to see if I can figure out the cmsis-dsp library for some filtering and such.  I think someone said something about a rabbit hole -- it does indeed seem to consume a fair bit of time.

gil

________________________________
From: greenkeys-bounces at mailman.qth.net <greenkeys-bounces at mailman.qth.net> on behalf of Harold Hallikainen via GreenKeys <greenkeys at mailman.qth.net>
Sent: Friday, March 18, 2022 7:44 AM
To: steve bennett <raleigh_ranger at yahoo.com>
Cc: greenkeys at mailman.qth.net <greenkeys at mailman.qth.net>
Subject: Re: [GreenKeys] Minimal DSP TU Working!

They did not have any DSP classes when I was in school long ago. In my
work, I worked with DSP consultants who made the chips do what I needed. I
then communicated with the chips over SPI for control. I am now trying to
learn some DSP. The TU seems like a good learning experience. With the
biquad code I found online, implementing biquad filters is pretty easy.
The code provides an easy way to initialize the filter and then a short
function to run on each sample. A lot of DSP stuff uses DMA ping pong
buffers and then processes the data in batches. In my TU, I am doing
everything on a sample by sample basis. The system uses a timer to
generate an 80 kHz PWM output. Every 10 cycles of that timer (8 kHz), an
ADC sample is pulled, the ADC restarted for the next sample, then the
sample run through the DSP code. I will be adding code to set a pin high
at the start of the DSP code and low on the way out so I can see how much
processor time is being taken.

This project is one of many, so at times it is slow going.

Harold


On Fri, March 18, 2022 6:13 am, steve bennett wrote:
>  Harold,
> Â  I took a DSP class in college. I wrote some code to process signals off
> line.How do you write code that works in real time?I'm sure entire books
> have been written on the subject so it would be hard to answerin a single
> email.
> -Steve
>     On Friday, March 18, 2022, 12:30:09 AM EDT, Harold Hallikainen via
> GreenKeys <greenkeys at mailman.qth.net> wrote:
>
>  I'm using Microchip MPLAB-X for a PIC32MZ microcontroller. The compiler
> is
> a microchip version of gcc.
>
> The biquad C code is attached.
>
> Harold
>
>
> On Thu, March 17, 2022 9:01 pm, brad at bfayette.com wrote:
>> Can you tell us what your dev environment is, and which compiler? Also,
>> I
>> am interested in the biquad class. Thanks!
>>
>> Regards,
>> Brad Fayette
>> Blessed are the geeks, for they shall inherit the earth.
>> Sent from my MEK6800D1.
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