My New PCB Prototypes
Posted: Wed Aug 01, 2018 8:36 pm
Hey all,
For a couple of months now I've been working on some new boards that I think will be useful in non-AIO builds. I think there are plenty of AIO boards out there now, and I have no intention of competing with Kite's. But I still think these will be pretty handy, especially for first-time builders.
Since I started building GBZs, I've thought the biggest drawback of the Pi0w is the single USB port. Stripping down USB hubs is annoying, though in some cases it's pretty easy, plus you get some extra wire out of the deal. The compact options like the nanohub and Tinkerboy's bare hub are the perfect size for a GBZ build, but (even when they're in stock) you can get 3-4 strippable hubs for similar cost. (And the Tinkerboy one wasn't even an option when I started working on this.) So I came up with some options.
First, this was pretty much my prototype design. It's a basic 4-port USB 2.0 hub. Like other FE1.1s hubs, it doesn't work with combinations of high speed and full speed devices, but it seems to do the job nevertheless.
It's small, at 0.5x1.4 inches, but that's pretty boring, plus you still need to run 4 wires to it, taking up space inside the build. So how about we kick things up a notch, and alleviate that problem?
Now we're talking. This one sits flush with the back of the Raspberry Pi. It connects to the same four pads we're used to. A couple of the boards to follow also connect this way, because having tried it a few times I think it works fantastically.
As you might've been thinking, this is probably best suited if you're using a screen bracket like the one Hoolyhoo came up with that places the SD card at the contrast port. You'd be right, with the next couple of boards especially-so. The one above doesn't necessarily need to be placed there, but I'd recommend it for the next two.
This one is really intended toward new GBZ builders. It sheds the USB hub and focuses on simply providing easy pads for connecting the most-commonly-used attachments, like a composite display, PWM audio, an ADS1015 and safe shutdown button. And I'm sure you've noticed the through-hole pads at the bottom for connecting the button board to the GPIO pins without long wires. If the Pi0w is aligned with the contrast port, those wires only need to be about a half- to one-inch long. (picture later) I went with the ABXY positioning used by the common button board sold on Amazon (which was my first build) and also included with a bunch of kits (like the ones from thegodofgaming on ebay). It still works great with other arrangements though.
You might also notice the lack of connections to the GPIO pins at the top. I wanted to leave the SPI pins open, so this will work with VeteranGamer's SPI connectors. And that space in the middle of the board... It *should* be possible to solder down that first USB hub I showed there. (I haven't had the opportunity to test that yet.) And if you plan to use a Teensy or Pro Micro, you don't even need to solder most of the GPIO pins.
Next up is, in my opinion, the best of the bunch. It combines the last two boards, and adds in USB audio using the CM102S+ audio chip, which has an integrated amp. This addresses the second biggest issue with the Pi0w (I think), and that's that the PWM audio isn't good enough. In my testing, the Hub+CM102 draws 35-50mA, and can go up to 60mA if you crank it up. Here it is:
But wait, there's more! These are still prototypes, but I designed a couple SPI screen connectors also. They require wires to be run to the GPIO pins on the Pi, so they're not as convenient as VeteranGamer's design, but that also makes it so the parts should be easier to acquire.
And lastly, before I post a few real-world photos, here is the common ground PCB I came up with. I wanted to put a fun and unique (I hope) spin on it, and also have one with six button pads where the through-hole pins all line up with the earlier boards. Tada!
I seriously considered putting holes in the extra buttons to use as a drill guide, but the darn hockey puck tried to bite my hand off.
Here's my initial prototype of the USB backplate. This one only has the USB hub without the CM102. I came to the conclusion that having the USB hub, with GPIO inputs and PWM audio kind of defeated the purpose. In this iteration, I was powering the hub with the 3.3V, which required 1 less capacitor. When I added the CM102 audio, I really didn't have room to run those extra traces and switched it all to 5V. You can just make out the micro-USB power port on the Pi underneath.
And here's my minimal USB hub prototype with the CM102S+ test. I was trying out different resistors and capacitors. Using the 47uF capacitors just before the speakers, it makes a vwooosh sound while powering up. I'm expecting to use smaller ones on the PCB.
Here's one of the builds I'm putting together now using the twin of the above prototype board. (Can't let them go to waste, right?) You can see just how short the wires running to the button board are. That's a prs-tech button board.
And finally, here's the reflow oven I built for baking all that SMD goodness. This was a fun build. I did put a stainless steel mesh over the baking rack since that picture though, because some of these boards are pretty small and can fall through without it while trying to place the PCB. (Gravity, amirite?) At first I had considered the one on Amazon that was just over $200 and still needed a bunch of modifications, but then I found just the right video on youtube. It was the best video I'd seen for building a reflow oven, from about four years ago, and it only had a couple hundred views. The new parts for this one ran just under $100, and I used just a few parts I had lying around.
My next batch of prototype PCBs is set to arrive next week, which includes the board that contains the combined USB hub+CM102, the button board, and the SPI boards. I've got a small batch of the minimal hub (blue), backplate USB (green) and basic GPIO assist boards too, so hopefully those'll get into the hands of the community sooner rather than later.
I'd love to know what you think. Thanks!
PS. And I'd like to give a special thanks to this outstanding community and my appreciation for your willingness to answer questions, share information, and help everyone learn new skills so they go beyond their limits. Since I started working on these builds, it's motivated me to learn Sketchup (I'd never designed a 3d model before), and I'd never designed a PCB before either, or understood nearly as much about electronics or soldering as I do now. And I know I've still got a long way to go, but it's a journey I'm looking forward to.
Also, please let me know if you have any questions. I'm usually hanging out in the Retropie Handhelds group on Facebook these days, but I'll keep an eye on this thread.
For a couple of months now I've been working on some new boards that I think will be useful in non-AIO builds. I think there are plenty of AIO boards out there now, and I have no intention of competing with Kite's. But I still think these will be pretty handy, especially for first-time builders.
Since I started building GBZs, I've thought the biggest drawback of the Pi0w is the single USB port. Stripping down USB hubs is annoying, though in some cases it's pretty easy, plus you get some extra wire out of the deal. The compact options like the nanohub and Tinkerboy's bare hub are the perfect size for a GBZ build, but (even when they're in stock) you can get 3-4 strippable hubs for similar cost. (And the Tinkerboy one wasn't even an option when I started working on this.) So I came up with some options.
First, this was pretty much my prototype design. It's a basic 4-port USB 2.0 hub. Like other FE1.1s hubs, it doesn't work with combinations of high speed and full speed devices, but it seems to do the job nevertheless.
It's small, at 0.5x1.4 inches, but that's pretty boring, plus you still need to run 4 wires to it, taking up space inside the build. So how about we kick things up a notch, and alleviate that problem?
Now we're talking. This one sits flush with the back of the Raspberry Pi. It connects to the same four pads we're used to. A couple of the boards to follow also connect this way, because having tried it a few times I think it works fantastically.
As you might've been thinking, this is probably best suited if you're using a screen bracket like the one Hoolyhoo came up with that places the SD card at the contrast port. You'd be right, with the next couple of boards especially-so. The one above doesn't necessarily need to be placed there, but I'd recommend it for the next two.
This one is really intended toward new GBZ builders. It sheds the USB hub and focuses on simply providing easy pads for connecting the most-commonly-used attachments, like a composite display, PWM audio, an ADS1015 and safe shutdown button. And I'm sure you've noticed the through-hole pads at the bottom for connecting the button board to the GPIO pins without long wires. If the Pi0w is aligned with the contrast port, those wires only need to be about a half- to one-inch long. (picture later) I went with the ABXY positioning used by the common button board sold on Amazon (which was my first build) and also included with a bunch of kits (like the ones from thegodofgaming on ebay). It still works great with other arrangements though.
You might also notice the lack of connections to the GPIO pins at the top. I wanted to leave the SPI pins open, so this will work with VeteranGamer's SPI connectors. And that space in the middle of the board... It *should* be possible to solder down that first USB hub I showed there. (I haven't had the opportunity to test that yet.) And if you plan to use a Teensy or Pro Micro, you don't even need to solder most of the GPIO pins.
Next up is, in my opinion, the best of the bunch. It combines the last two boards, and adds in USB audio using the CM102S+ audio chip, which has an integrated amp. This addresses the second biggest issue with the Pi0w (I think), and that's that the PWM audio isn't good enough. In my testing, the Hub+CM102 draws 35-50mA, and can go up to 60mA if you crank it up. Here it is:
But wait, there's more! These are still prototypes, but I designed a couple SPI screen connectors also. They require wires to be run to the GPIO pins on the Pi, so they're not as convenient as VeteranGamer's design, but that also makes it so the parts should be easier to acquire.
And lastly, before I post a few real-world photos, here is the common ground PCB I came up with. I wanted to put a fun and unique (I hope) spin on it, and also have one with six button pads where the through-hole pins all line up with the earlier boards. Tada!
I seriously considered putting holes in the extra buttons to use as a drill guide, but the darn hockey puck tried to bite my hand off.
Here's my initial prototype of the USB backplate. This one only has the USB hub without the CM102. I came to the conclusion that having the USB hub, with GPIO inputs and PWM audio kind of defeated the purpose. In this iteration, I was powering the hub with the 3.3V, which required 1 less capacitor. When I added the CM102 audio, I really didn't have room to run those extra traces and switched it all to 5V. You can just make out the micro-USB power port on the Pi underneath.
And here's my minimal USB hub prototype with the CM102S+ test. I was trying out different resistors and capacitors. Using the 47uF capacitors just before the speakers, it makes a vwooosh sound while powering up. I'm expecting to use smaller ones on the PCB.
Here's one of the builds I'm putting together now using the twin of the above prototype board. (Can't let them go to waste, right?) You can see just how short the wires running to the button board are. That's a prs-tech button board.
And finally, here's the reflow oven I built for baking all that SMD goodness. This was a fun build. I did put a stainless steel mesh over the baking rack since that picture though, because some of these boards are pretty small and can fall through without it while trying to place the PCB. (Gravity, amirite?) At first I had considered the one on Amazon that was just over $200 and still needed a bunch of modifications, but then I found just the right video on youtube. It was the best video I'd seen for building a reflow oven, from about four years ago, and it only had a couple hundred views. The new parts for this one ran just under $100, and I used just a few parts I had lying around.
My next batch of prototype PCBs is set to arrive next week, which includes the board that contains the combined USB hub+CM102, the button board, and the SPI boards. I've got a small batch of the minimal hub (blue), backplate USB (green) and basic GPIO assist boards too, so hopefully those'll get into the hands of the community sooner rather than later.
I'd love to know what you think. Thanks!
PS. And I'd like to give a special thanks to this outstanding community and my appreciation for your willingness to answer questions, share information, and help everyone learn new skills so they go beyond their limits. Since I started working on these builds, it's motivated me to learn Sketchup (I'd never designed a 3d model before), and I'd never designed a PCB before either, or understood nearly as much about electronics or soldering as I do now. And I know I've still got a long way to go, but it's a journey I'm looking forward to.
Also, please let me know if you have any questions. I'm usually hanging out in the Retropie Handhelds group on Facebook these days, but I'll keep an eye on this thread.