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mozzie
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Joined: 15/06/2020
Location: Australia
Posts: 142

Posted: 02:07am 29 Mar 2023

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@Stanleyella
That filter does work exceedingly well, I too have just put one together and it is far better than any of the other R/C filters mentioned. As Volhout suggests, try some music but can I suggest posting the results in the Low Pass Filter thread that has been started.

@Phil99
The PWM block in the RP2040 does have registers for phase control but not for the individual outputs of a single slice (if I'm reading it correctly) so only logical inversion of each output is possible.

Using Address &h40050000 (PWM0 control register)
&h01 is normal mode
&h05 is Invert output A
&h09 is Invert output B

This also assumes that the MMbasic program doesn't re-write this value at some given time and reset it, only Peter or someone who can read the source code can answer that, hence the reason for the original question. So far its been fine.

I found the info in the datasheet, but as JohnS suggests, there will be info out there on the interwebs.

Regards,
Lyle.

phil99

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Joined: 11/02/2018
Location: Australia
Posts: 2642

Posted: 03:03am 29 Mar 2023

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Thanks Mozzie and JohnS for the information.

homa

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Joined: 05/11/2021
Location: Germany
Posts: 471

Posted: 08:40pm 29 Mar 2023

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Hello,
the days I finally had time to build the sound output (low pass filter) for the PicoMite VGA.
Picture 1, 2 and 3:

Question to @Stanleyella:

stanleyella said

Is the used 3.5 mm stereo socket as in the picture of you to use immediately without modification on the breadboard of you?
On mine (https://www.reichelt.de/klinkeneinbaubuchse-3-5-mm-stereo-ebs-35-p7301.html) I had to clip off pins and drill additional holes beside the pitch :-(

The sound quality is as noted really very good.
However, there are short noise at the beginning of a wav playback. Also, the output on the mixer is very noisy. The gain must remain quite low.
I have here a recording as an example: PlaySoundNoise.zip

Is it possible to improve this behavior?

I still saw these threads:

https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=15758
https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=15716
https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=15771 I also had the question ...
https://www.thebackshed.com/forum/ViewTopic.php?FID=16&TID=15748

Greetings
Matthias

Edited 2023-03-30 06:49 by homa

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