real time page ?

3 years 9 months ago - 3 years 9 months ago #2110 by phil123456
real time page ? was created by phil123456
Hello,

I tried to find the page talking about optimizing the RPI

can someone post the link to me ?

can't find it anymore

thanks

edit : this concerns pedal pi with rpi zero, not pedal pi uno, dont even know what that is

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3 years 9 months ago #2113 by phil123456
Replied by phil123456 on topic real time page ?
anybody ?

so far I patched the kernel for RT and managed to obtain 5 Mhz GPIO flip flop

I got a clean sound just forwarding input to output, but trying to do decent DSP effects without nois is impossible with the provided code

when it's about reading the mcp3002, that thing is super slow

anyone made any improvement to the code ?

thanks

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3 years 9 months ago #2116 by Boris
Replied by Boris on topic real time page ?
I wrote a long code for 4 independent effects.
The conversion delay is 30 μs. This is quite sufficient to get a clean enough sound.
As I understand it, this time is obtained due to the output conversion. Optimization of the ADC does not lead to faster conversion.
I’m making a device for a bass guitar, maybe for this reason speed is not so important for me.

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3 years 9 months ago - 3 years 9 months ago #2119 by phil123456
Replied by phil123456 on topic real time page ?
yes, I noticed high frequencies were chopped off

but the issue is that, even by recompiling linux with the real time patch, I still had the sound chopped off for 50ms every second
could'nt figure out why

so now I go bare metal (no linux) just wrote a short little program , and it's the only thing that runs

I had to port the bcm2835 lib (keeping only SPI and PWM features)

still the high frequencies are hard to keep, the issue comes mainly from the mcp3002 wich is quiet slow

but the fact is that pedal pi is definitely not a ready to go solution to make guitar digital effects

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3 years 9 months ago #2120 by Boris
Replied by Boris on topic real time page ?
Sorry my english is not very good.
Pi pltforma is not very suitable. It does not have a hardware ADC and therefore requires additional components. The processor clock speed does not matter since you still run into the speed of ports working with the ADC. Considering all the above, 50 μs is an excellent result.
I settled on a hardware solution using Arduino. I am using the nano version. If you want to get really high quality sound, the DUO version is suitable for you. It has unsurpassed performance of a 12-bit ADC and an integrated hardware DAC.

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3 years 9 months ago #2121 by phil123456
Replied by phil123456 on topic real time page ?
50ms, not µs

first I used a teensy 3.6, I need something small, but the ADC is garbage on that board

so I have no choice but using a raspberry pi. I also found other small boards, but RPI has a 1ghz processor, I count on it :-)

I still can use i2s instead of pci if it's too slow

what I dont understand is that pedalpi is virtualy useless in the world of autio, it's too slow and makes too much noise

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3 years 9 months ago - 3 years 9 months ago #2122 by Boris
Replied by Boris on topic real time page ?
As an artist to an artist, I would use PI as a control element that will provide a large screen, mouse and keyboard, and I would perform sound conversion using Arduino DUO.
We get a high hardware speed DUO and user-friendly interface under the control of PI.


Here is my idea using NANO. I use a small 64 * 128 screen and an encoder with a button to select the operating mode. I use about 30% of the controller resources NANO.
Pi is an incredibly powerful platform for this task, but it is loaded with the OS because working with it is not very effective.

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