My New PCB Prototypes

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infinitLoop
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Re: My New PCB Prototypes

Post by infinitLoop » Fri May 03, 2019 1:11 pm

RxBrad wrote:
Fri May 03, 2019 12:58 pm
infinitLoop wrote:
Fri May 03, 2019 12:49 pm
btw - did you go for the spi screen, or are you going to do composite?
I'm using one of the Gearbest composite screens (and I'm planning to do this brightness adjustment mod -- though I'll need to set it up with a different PWM).

Having used both, I actually prefer the simplicity of the composites when I need to fiddle with graphics settings inside/outside Libretro. And maybe it's just placebo effect, but I feel like a lot of games run slower through the Pi Zero on SPI.
that's interesting. i just tried spi for the first time, and i felt like that affected performance too, especially on the 16bit games, compared to the composite builds i've done, but i wasn't sure if it was just me, or something i might have messed up on the build, or what. plus the interlacing affect / view angle for the one i got is terrible, since i didnt realize those were meant to be mounted vertically normally. i ordered another with "wide angle" viewing so hopefully that helps with the next one.

Dividion
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Re: My New PCB Prototypes

Post by Dividion » Fri May 03, 2019 1:23 pm

On the Ultra, GPIOs 4, 17 and 27 are all circled, so you should solder those.
4 is set as the "switch off" (or "shutdown") pin
17 is set as the "signal on" (or "keep alive even if the power switch is off") pin
27 is set as the "toggle battery icon" pin

The two Safe Shutdown pads on the face of the Ultra are for connecting a button that you can use for toggling. That uses GPIO 27.

If you're using the MintyBatteryMonitor, you'll want to update the script to make sure the toggle button is GPIO 27, and the shutdown button is GPIO 4.

The /boot/config.txt should contain the line to power off GPIO 17 when the shutdown cycle completes:
dtoverlay=gpio-poweroff,gpiopin=17,active_low="y"

If you don't have a separate toggle button for GPIO 27, you can dual-purpose GPIO 4 so that "when_pressed" it acts as the toggle button, and "when_held" it triggers the shutdown. Then, if you slide the power switch off and then back on really quickly, it'll toggle the battery icon. But you'll want to modify the monitor script to either slow down the polling (increase the sleep timers to a few seconds) or ignore sudden radical changes so that you don't accidentally trigger the system off while just trying to toggle the battery icon. (increasing the sleep timers from 0.3 to 2 or 3 seconds still carries a risk of triggering a shutdown, but requires less coding) :)
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RxBrad
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Re: My New PCB Prototypes

Post by RxBrad » Fri May 03, 2019 1:38 pm

Thanks.. So if I understand correctly:

If configured as Toggle=4, Shutdown=4 (plus slow the polling)
- Slide power switch off: initiates safe shutdown
- Slide power switch on: turns unit on
- Quickly slide power switch off & back on: toggle battery monitor

If configured as Toggle=27, Shutdown=4
- Slide power switch off: initiates safe shutdown
- Slide power switch on: turns unit on
- Press button wired to GPIO 27: toggle battery monitor

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Re: My New PCB Prototypes

Post by Dividion » Fri May 03, 2019 2:42 pm

RxBrad wrote:
Fri May 03, 2019 1:38 pm
Thanks.. So if I understand correctly:

If configured as Toggle=4, Shutdown=4 (plus slow the polling)
- Slide power switch off: initiates safe shutdown
- Slide power switch on: turns unit on
- Quickly slide power switch off & back on: toggle battery monitor

If configured as Toggle=27, Shutdown=4
- Slide power switch off: initiates safe shutdown
- Slide power switch on: turns unit on
- Press button wired to GPIO 27: toggle battery monitor
Correct!

If you don't care about the battery monitor icon, you can just use the two lines in the config.txt which makes things super easy. The Ultra has a built in ADS1015 though, so might as well use it. :)
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RxBrad
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Re: My New PCB Prototypes

Post by RxBrad » Wed May 22, 2019 8:47 am

So, I'm about to start soldering up my kit. One question: what's the best way to go about soldering the through-holes on the Pi Zero to the through-holes on the GPIO Assist? I get the impression that there's no header involved? Attaching a through-hole to a pad, I get. This: I feel like it's gonna be tough to simultaneously heat up the contacts on both boards and get a good solder.

Maybe I'm just overthinking it...

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infinitLoop
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Re: My New PCB Prototypes

Post by infinitLoop » Wed May 22, 2019 9:02 am

RxBrad wrote:
Wed May 22, 2019 8:47 am
So, I'm about to start soldering up my kit. One question: what's the best way to go about soldering the through-holes on the Pi Zero to the through-holes on the GPIO Assist? I get the impression that there's no header involved? Attaching a through-hole to a pad, I get. This: I feel like it's gonna be tough to simultaneously heat up the contacts on both boards and get a good solder.

Maybe I'm just overthinking it...
what i usually do is use some screws and nuts to hold the pi against the board, then using fine solder, solder one side, then flip it over and do the other a little to make sure its good. I push and hold the tip in the hole for a second or two first to heat it up (and a lot of times, just push and hold the back side when i flip, unless the solder looks low). Usually you don't need a whole lot of solder, so i'd err on the side of a little less, because you can also just re-flow it or add a little if the connection isn't great. I haven't had a case where I've bridged anything, except the usb once when i shifted the board after lining it up, but if you have the pi and board snug, i think it's hard to bridge the gpio.

you could use a header tho, if you wanted to clip off all the pins, but i don't think you need it.

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Re: My New PCB Prototypes

Post by Dividion » Wed May 22, 2019 11:16 am

I agree with what inifitLoop just wrote. I've tried a bunch of different variations. I normally stick some header pins through the GPIO holes to get a good alignment, and then start with the two USB pads, since they're the closest together. You want to make sure you don't see any of the Pi's green PCB at the bottom before you solder those.

Screwing the boards onto a screen bracket helps keep them together. (It doesn't need to be in the shell.)

For the GPIO holes, here are a couple of methods that I've had good success with:
1 - Using 0.8mm solder and a not-too-fine conical tip, poke it through the hole from the Pi side until it's just at the edge of the other side, and then press the soldering iron into the hole all the way. Feed the solder in until it's a liquid at the edge of the Pi. Withdraw the iron, use it to cut the solder wire (which should be stuck on the Pi side), and then poke in from that side for a second. You should have a good connection all the way through.
2 - Using a fine conical tip, heat up the hole and add solder on the GPIO Assist side (since you only need to add it to the marked holes). Then flip the board and add solder to the same holes on the other side. Since it's a fine soldering tip, you should be able to press it in and make sure both sides achieve good contact.

After you're done, you can check for continuity from the button board inputs at the bottom of the GPIO Assist board to the GPIO pads on the Pi side. You should be able to reflow any incomplete connections. You can also check for any bridges between adjacent pins, but keep in mind that the Ultra board can report a false positive because of the safe shutdown at GPIO 4 (pin 7 I think) which connects to ground when the switch is in the off position.
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infinitLoop
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Re: My New PCB Prototypes

Post by infinitLoop » Wed May 22, 2019 11:49 am

Dividion wrote:
Wed May 22, 2019 11:16 am
After you're done, you can check for continuity from the button board inputs at the bottom of the GPIO Assist board to the GPIO pads on the Pi side.
i was coming back to say that :D definitely make sure you use the pi side when checking.

it's not too hard as long as you get that initial alignment, and you have something keeping it in place and against the pi. the usb is really the only tricky one, so definitely do that first. something like half a mm is all it takes to shift those and bridge it.

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Re: My New PCB Prototypes

Post by RxBrad » Thu May 30, 2019 9:32 am

Hey, Dividion.. I notice that you have a jumper on the DMG button board to combine the L & R audio channels for mono speaker output. I'm wondering if adding resistors into the mix might be advised to prevent backfeeding into the L/R channels of the onboard amp? Not sure if there's some sort of protection already built in for this.

More info here: http://www.rane.com/note109.html

Image

Dividion
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Re: My New PCB Prototypes

Post by Dividion » Thu May 30, 2019 12:00 pm

RxBrad wrote:
Thu May 30, 2019 9:32 am
Hey, Dividion.. I notice that you have a jumper on the DMG button board to combine the L & R audio channels for mono speaker output. I'm wondering if adding resistors into the mix might be advised to prevent backfeeding into the L/R channels of the onboard amp? Not sure if there's some sort of protection already built in for this.

More info here: http://www.rane.com/note109.html

Image
You can definitely throw a resistor in there if you want, but I don't think it's necessary. There are pull-down resistors on the outgoing channels after the amp and I haven't run into (or heard of anyone else having) any backfeeding problems. :)
Check out my store for GBZ boards and accessories: http://pocketadventures.com

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