Pi in a Gameboy Advance Build - WIP
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Some investigation into using capacitors to clean up electrical noise prompted me to try attaching a 0.1 µF capacitor to the power input of the amp. I can't tell how much it helped, but that combined with the 10-Ohm resistors coming off the headphone jack to bridge the stereo into mono has sound that has a level of hissing that I would say won't bring this project to a halt, but I am going to look into buying some ferrite beads to use on the power input as well as the speaker output to try to help clean things up a bit more.
Next up it's a matter of the two things I've been putting off: The power circuit (soft shutdown, low battery warning/shutdown) or modding the case...
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Why would you need a sound card for a Pi 3? couldn't you just wire into the headphone jack pins and get the sound that way? Or is that not possible? Anyway the project is looking fantastic BTW. =]
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@thedudester80 It's possible. I initially decided to use USB sound to try to reduce the hiss I was getting when I was doing some testing. The USB soundcard has zero hiss, and for how cheap it was, sounds really great with these old games. Considering that I'm getting some hiss with the Adafruit amp even with the USB soundcard as the source of the audio I'm not sure if it would be better or worse going right off the Pi. It might be worth trying things without the USB soundcard and saving that for my Gameboy Color project. I'll have to think about it.
And thanks for the kind words. This is a whole lot of figuring it out as I go, and I really have no idea what I'm doing.
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@obsidianspider ooooooh oooooooh oooooh lightbulb moment! Your currently powering the amp from the 5v input to the pi. What happens if you try powering the amp from the usb 5v output? Maybe that is cleaner?
want to get a tft into your project, look no further than here https://retropie.org.uk/forum/topic/7464/ili9341-tft-screen-guide
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@moosepr it's worth a try. The amp itself is rated to pull up to 800mA at full tilt, it I'm running a tiny speaker and the whole system is only going to be getting 1A from the PowerBoost, so the fact that the USB ports only output 500mA max shouldn't be an issue. I think what I'll try is tagging off the power that's connected to the sound card, at the sound card. Since they'll both be next to each other inside the case that would also cut down on wires in the case if this works. I'll report back, but first, some coffee.
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@moosepr Going to USB for power has basically eliminated the CPU/disk access related buzzing! I did leave the 0.1 µF capacitor in there, as I figured it can't hurt. There's still a little bit of hiss from the amp (just general background white noise when no sound is playing), but I'm thinking some ferrite beads on the speaker wires will take care of that.
Now to read up on options for power circuitry…
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Up next: Pi in a DS.
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I remember hearing something about using a capacitor for a hiss noise for your amp. I'm not sure what kind off the top of my head but it might be something to look into.
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@itsnitro Hahaha, I have already thought of that one!
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@moosepr Huh.
But here's the thing; RetroPie needs to be compatible with 2 monitors.
Cause ya know, the DS has two screens. -
@itsnitro yeah it wouldn't be a 2 screen job. More like the people who cut the top screen off a DS to turn it into a skinny square GBA
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There could be a way to remove the screen on the bottom and keep the one at the top, keeping the original shape of the DS. All we are doing is just removing the screen.
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@itsnitro said in Pi in a Gameboy Advance Build - WIP:
@moosepr Huh.
But here's the thing; RetroPie needs to be compatible with 2 monitors.
Cause ya know, the DS has two screens.Might be possible for a 2ds project then? If I remember correctly the screen for it is just one big one.
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There's a 2DS.
Still has 2 screens, but it would be considerably easier to fit everything inside. Just a thought. -
@itsnitro I believe the 2DS has 1 screen
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It looks like the 2DS uses one screen. If someone wants to put a Pi in one, let us know how it goes.
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@itsnitro It should be one big tn panel inside. I believe they did this to save costs.
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Oh, I did not realize that.
So, what would fit? A Raspberry Pi 3? Or is that too big? -
I finally got around to shopping for some ferrite beads today, and wow, shop around online. The ones I was looking for were part number 86-1570 as referenced on sudomod. I found a shop in Connecticut that had them for $2/pack instead of the $9/pack they were selling for on eBay. If I lived anywhere near a Fry's, that would have been an option too, but sadly, I do not. They should be here in a few days to a week. I also see that Camble's safe shutdown circuit will fit in my case as it's 30mmx15mm. Hopefully they will be available for purchase soon as that will solve my "how do I shut this thing off nicely?" problem.
I'm not sure how I want to go about getting the LED to work. Ideally I'd love it to display in the original spot and be green when on and orange when charging, but I'm not sure if there's a good way to go about doing that.
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I love when parts come in the mail!
My ferrite beads arrived, and wow, they're really tiny. I didn't get out my micrometer, but a quick measurement with a ruler has them at just a shade over 3mm in diameter.
I also got a USB current tester. I wanted to see how much this rig was pulling with the screen, USB sound card, amplifier, and wifi enabled, and with SFA 3 playing on lr-mame2003 and the amp turned ALL the way up, it was peaking at 520mA at 5V. I don't think I'll be having issues with the PowerBoost 1000c not being able to keep up.
I did find that when I switched over to lr-genesis-plus-gx, again, with the volume totally maxed out, that I would get the lightning bolt, the red light would blink, and things would sputter. I turned down the volume at the knob (not on the amp itself) and things cleared up. That told me that the amp was the issue. Even though my current tester said the whole system wasn't drawing more than 460mA at the time, I know that the USB ports are limited in power output, and since I have to power the amp from USB to avoid the buzzing from the power supply/SOC, I decided to see if increasing the maximum output to the USB ports would help.
I set
max_usb_current=1in/boot/config.txtand rebooted. Same problem. I then turned down the volume on the amplifier from "all the way up" (It doesn't go to 11), down to about half way, and everything works fine, no lightning bolt, even wit the volume knob turned all the way up and the ALSA mixer turned up to 80.With the amp setting dialed in I decided to see how much power everything would use over time. Letting Ghouls 'n Ghosts run its demo loop in lr-genesis-plus-gx for 30 minutes, with the volume all the way up, I saw on the current tester that it used 244mA at 5V. I'm not sure how to convert that to 3.7V, or to factor in the efficiency of the PowerBoost, but with a 2500mAh battery, I should get a few hours of play time out of this. At least I think so.
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