PWM Audio causing screen noise

[doomydoomer]

I've been having an issue with PWM audio causing screen noise/static/lines/etc win my Gameboy Zero. My GBZ setup:
- Raspberry Pi Zero
- Adafruit TFT composite screen with 5v mod (same as Wermy's build)
- Adafruit PowerBoost 1000c
- Adafruit 2600 mAh battery
- Helder's AIO (v2) board
- audio dither is set to 1 in my config

The problem:



When I remove the PWM GPIO wires from my build, the static completely goes away - zero noise on screen. I've also removed the AIO board from the equation by going directly to the speaker and as soon as the PWM wires are connected I see the static again. I've swapped wires, isolated wires from the components, checked soldering points (I'm not new to soldering and have been doing it since 2003 when I worked with Xenium and Xecuter chips). My multimeter gives me a steady 5.15v from the Adafruit powerboost 1000c 5v line out. And finally, I do not see this issue via HDMI even with PWM audio forced. I have a spare crap screen from Amazon which exhibits the same static on screen ruling out the Adafruit screen as being defective or wired incorrectly for the 5v mod. This leads me to believe the combination of the composite screen and PWM Audio is the issue but outside of that general assumption, I can't seem to figure out how to fix it. I've search this forum and in general via Google but there doesn't seem to be anything exactly like this. Has anyone else seen this on their builds?

Just an FYI, I'm not new to the Rasp Pi, moding, soldering, small electronics scene. I've built a few different Raspberry Pi projects over the years using the Pi 1, Pi 2, Pi 3, and Pi Zero but this is a new one for me.

[flashpc]

I too am having the same issue, the screen is perfectly clear if pmw is not in use.

I believe I read in a previous post that moving the ground away from the composite output can introduce interference. I doubt this is the cause but there must be some sort of interference from the pmw audio.

I am also using Helders AIO board with the integrated audio amp.

[doomydoomer]

I believe I read in a previous post that moving the ground away from the composite output can introduce interference. I doubt this is the cause but there must be some sort of interference from the pmw audio.

I've tried a bit of everything including moving the LCD ground to and from the Pi but it didn't help.

I am also using Helders AIO board with the integrated audio amp.

Are you getting a good amount of static or noise over the headphone jack?

[flashpc]

Are you getting a good amount of static or noise over the headphone jack?

TBH I didn't check the headphone jack, as the speaker show'd no real issue, sorry

[doomydoomer]

No problem. And for what it's worth, I have no issues with volume coming out of my speaker either.

[dezent]

I have the same issue.
"Waves" on the screen like the "channel" isn't set 100% - just very close ...
Sometimes more sometimes less.

This was my first and def last helder Build.... Just trouble no benefit. USB sucks, Sound sucks...So annoying! This is my 8th GBz btw.

[144TECH]

I have the same issue.
"Waves" on the screen like the "channel" isn't set 100% - just very close ...
Sometimes more sometimes less.

This was my first and def last helder Build.... Just trouble no benefit. USB sucks, Sound sucks...So annoying! This is my 8th GBz btw.

A composite screen is always vibrating, it's never gonna be still image, this is a fact.
Usb works brilliant, sound works brilliant, you just gotta know what you are doing.

[dezent]

I have the same issue.
"Waves" on the screen like the "channel" isn't set 100% - just very close ...
Sometimes more sometimes less.

This was my first and def last helder Build.... Just trouble no benefit. USB sucks, Sound sucks...So annoying! This is my 8th GBz btw.

A composite screen is always vibrating, it's never gonna be still image, this is a fact.
Usb works brilliant, sound works brilliant, you just gotta know what you are doing.

i have build 14 GBzeros.
With more or less all screen variants 320,640,HDMI
Original PCB, Helder V2.2, just button PCB
GPIO, Teensy and Arduino nano Pro
Blackberry Trackball
and maaany more variants

i think i do know what i am doing....

[144TECH]

I have the same issue.
"Waves" on the screen like the "channel" isn't set 100% - just very close ...
Sometimes more sometimes less.

This was my first and def last helder Build.... Just trouble no benefit. USB sucks, Sound sucks...So annoying! This is my 8th GBz btw.

A composite screen is always vibrating, it's never gonna be still image, this is a fact.
Usb works brilliant, sound works brilliant, you just gotta know what you are doing.

i have build 14 GBzeros.
With more or less all screen variants 320,640,HDMI
Original PCB, Helder V2.2, just button PCB
GPIO, Teensy and Arduino nano Pro
Blackberry Trackball
and maaany more variants

i think i do know what i am doing....

It's just composite screens that always flickering, you can see it when you look very close.
But you can use another wire with more ''wire'' inside, or re route the wire some other way beside the other components.
You are very fast building 6 gbz's in about 2 months ! so you probably figured it out already.

Greets 144Tech

[doomydoomer]

Just a quick friendly reply to all of this. My issue was not related to typical composite flicker. Once I moved away from PWM audio and Helder's onboard audio both my audio and video issues were resolved. For anyone with this issue, it's worth trying a USB audio solution.