Pi in a Gameboy Advance Build - WIP
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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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@obsidianspider looking good! I take it the beads have totally cured the sound issues?
The power calculations can be done simply. If we use basic wattage calculation. You half hour test used 250ma (rounded of course) so we can assume 500ma for the hour. If we multiply that by the voltage (in guessing 5.1, can't see the image right now) then that gives us a total of 2.55 watts.
We can then divide that by the battery voltage to reverse calculate it. The battery voltage will range from 4.2-3.2ish so if we use 3.7v as an average, we can take the 2.55 watts, divide that by the 3.7 and that gives us the magical number of 689mah so we can round that up to 700mah.
This may be slightly more in real world usage. Most boost converters loose some power in operation, but you should be over 3 hours with a 2500mah battery
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@obsidianspider
A "USB current tester" ... I didn't know such a thing like this existed...but I need one now!! -
@backstander they are petty handy. Nice and cheap, although I think mine reads about 10% low
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@backstander said in Pi in a Gameboy Advance Build - WIP:
@obsidianspider
A "USB current tester" ... I didn't know such a thing like this existed...but I need one now!!I'm also going to get a female JST connector and connect it to a female USB plug so I can test current draw directly from a LiPo.
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