[GUIDE] 3.5 inch HDMI Display - high energy usage

[salami738]

Great guide - Currently in process of modding the screen to use less power - Thank you for everyones work.

I had a question about the screen - Has anyone gotten HDMI audio working ?

I cant seem to get it to work - does it require the GPIO header to be plugged in ? From what i could tell thats only needed for touch screen options.

I was also unable to get anything from audio on both Ubuntu 16.04 and Mac osx Seirra - both detected (including the pi) that HDMI audio was there but I couldn't hear anything ?

Does it require a special driver or something - I didn't install the 99-fbturbo.conf-HDMI as it fails during the driver install. But isn't this just for touch screen stuff ? https://github.com/goodtft/LCD-show

I would prefer to use the HDMI audio that way I could get rid of the USB DAC I'm using - meaning no usb stuff for my build which would be a great power save.

I'm going to have a look at the HDMI DAC to Headphone IC skematics and see how that works.

Do you need to amplify the signal before hand ?

Hi, on my MPI3508 board the headphone jack worked without any problem. You don't need any drivers.
I tested with earbuds. If you want to drive a speaker you need an amplifier, e.g. a PAM8403 or something similar.

The GPIO is only for the touchscreen functionality. You need a driver for this, but I would recommend to remove the touchscreen layer to get a better picture. Touch is not really usable on this display size.

[salami738]

So I've been able to get the screen up and running - but during the last week I wasn't super careful with the screen and cracked it - at least I thought I had, and I did. I was able to solder off the screen which made desoldering the header alot easier. I've got another screen on order but I''d like to see if I can get a replacement screen minus the controller and solder it on - I would assume that they'd be fairly cheap. Would anyone know of a replacement, and where to buy it ?

I've found this one but Im not 100% sure if its suitable - will need to investigate more - but $10 is better than $30.
https://www.aliexpress.com/item/3-5-inc ... utifyAB=5
I'll upload some pics later with some board alterations.

Hi, maybe the thread https://sudomod.com/forum/viewtopic.php?f=53&t=4831 helps you identify the screen.
I had problems with a broken FPC connector and resoldered it.

I tried to find a replacement screen too, but didn't had any luck finding one. You need one with the exakt same controller and pinout.
On my screen there is no description about the used controller, I only know about the used leds (see picture in above link).

[Vineheart01]

Hey Salami, out of curiosity do you know the pinouts for the headphone jack?
I think i screwed up by pulling the jack off the board ahead of time lol. Having difficulty finding out what pinhole is what.

[salami738]

Hey Salami, out of curiosity do you know the pinouts for the headphone jack?
I think i screwed up by pulling the jack off the board ahead of time lol. Having difficulty finding out what pinhole is what.

Hi, i dont have the gameboy around currently. But you can use this image:

[Vineheart01]

well...thats unnerving...thats the pins i used.
Crap lol...

Ugh that means either the pins w/o the jack are different than just tapping off the top of the jack, i damaged it removing it (doesnt look like i damaged it), or my amp is messed up. I hear popping noises in the speaker, which is usually a sign of bad wiring work.

[salami738]

well...thats unnerving...thats the pins i used.
Crap lol...

Ugh that means either the pins w/o the jack are different than just tapping off the top of the jack, i damaged it removing it (doesnt look like i damaged it), or my amp is messed up. I hear popping noises in the speaker, which is usually a sign of bad wiring work.

Hi, why don't you soldered the cables on top of the jack. Would have saved you a lot of work

You can check the following: Use a multimeter in AC mode between the GND and LEFT or RIGHT.
Then turn on the output by starting a game.
If you measure AC voltage higher than a few millivolt you have a good chance, that the display sound output is ok.
Then try to connect it to another amplifier or cut the cord of an old headphone and connect it.

Hope this helps, fingers crossed!

[moosethemucha]

So I've been able to get the screen up and running - but during the last week I wasn't super careful with the screen and cracked it - at least I thought I had, and I did. I was able to solder off the screen which made desoldering the header alot easier. I've got another screen on order but I''d like to see if I can get a replacement screen minus the controller and solder it on - I would assume that they'd be fairly cheap. Would anyone know of a replacement, and where to buy it ?

I've found this one but Im not 100% sure if its suitable - will need to investigate more - but $10 is better than $30.
https://www.aliexpress.com/item/3-5-inc ... utifyAB=5
I'll upload some pics later with some board alterations.

Hi, maybe the thread https://sudomod.com/forum/viewtopic.php?f=53&t=4831 helps you identify the screen.
I had problems with a broken FPC connector and resoldered it.

I tried to find a replacement screen too, but didn't had any luck finding one. You need one with the exakt same controller and pinout.
On my screen there is no description about the used controller, I only know about the used leds (see picture in above link).

Thank you for your help, I actually cracked the LCD screen on that one - and now I've actually severed that entire connector described in that thread - I'll continue my discussion there.

[salami738]

...

Thank you for your help, I actually cracked the LCD screen on that one - and now I've actually severed that entire connector described in that thread - I'll continue my discussion there.

You're welcome! The difficult part is now to find a exact matching replacement screen with the correct number of pins and pin assignment. Please post a link to a replacement screen, if you find one. I think you need one with 48 pins. Maybe you can ask a aliexpress-seller, usualle they are very helpful.

[Vineheart01]

Welp, i poked at it with a voltmeter and yeah i had the right pins (or atleast the 2 that are output, no idea if i got L vs R right lol).
I get this really weird popping noise when i play a game, making me think i wired something wrong or my amp is bad. Time to dig around and try to find veterangamer's audio rig, since im using that amp he likes from china, and verify i wired it right lol (i found one image of it before, but it was incorrectly written, he has another floating around somewhere where the vol knob is before the amp)

edit: its the amp....
Took the amp off the circuit and just direct drove the speaker from the audio jack on the screen. While its quiet as heck because no amp, i can hear it and its crystal clear.
Dang it...fortunately i do have a mono amp lying around i can use...guess my brother will have to deal with no stereo headphones lol
Thanks for the help!

[jakejm79]

You could try driving the headphone jack directly and then just using the amp for the speaker. Quite often there will be enough power to power headphones (I'm thinking ear buds) but not enough for a speaker.