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Forum Index : Microcontroller and PC projects : 5in SSD1936 + PGA2350B = A fun sort of a design. :)
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
This is a design that I started ages ago but never got anywhere with it. The tracks just wouldn't work out. A few days ago I realized that the answer is to put all the components between the PCB and the display and mount the display on 15mm spacers. The back of the PCB has nothing mounted on it unless you add an optional expansion connector. 16-bit parallel display, of course. I had enough GPIO pins to play with. :) It's still at the design stage so nothing is fixed yet.   EDIT: Incidentally, just in case anyone is wondering at my choice of mini USB and the PGA2350B, it's because I already have them. :) Additionally, soldering a USBC socket to a PCB is something of a challenge and only for masochists! The on-board LED can be either a 3mm LED connected as a Heartbeat indicator or a WS chip lifted off a piece of strip, in which case it's useless for Heartbeat but you can have pretty colours. :) Edited 2025-08-29 03:59 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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panky Guru Joined: 02/10/2012 Location: AustraliaPosts: 1116 |
Mick, I have successfully soldered down to 0.4mm by hand but not had any experience with ball grid - do you flow solder in from the back? Doug. ... almost all of the Maximites, the MicromMites, the MM Extremes, the ArmMites, the PicoMite and loving it! |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 1511 |
You use regular headers. Can be a bit of a struggle to pull out if needed. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
It's not a ball grid, Doug. The PGA2350 is a module from Pimorini. It comes without any headers soldered on. I used the "snap off" turned pin headers. The 2-row ones don't just snap off, by the way, they are a bit of a pig! To use them on a PCB plug the male and female headers together, drop them into the board, put the module onto them, solder a pin on each, turn it over, solder a pin on each on the bottom with some pressure on. That gets everything aligned. Now you can solder them properly. Once they are soldered in and correctly aligned they aren't too bad to unplug. It takes a lot of pressure to plug in so many pins though. Last time I put the pcb on the floor, put the module onto it carefully then pressed it in with my foot! Everything still worked. :) Soldering BGA is best done on a hot plate. Put the solder paste on, put the board on the hot plate, align the chip and switch the hot plate on. Let it cool before disturbing it. It's also the safest way to get the things off as even hot air puts too much thermal stress on some components. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| dddns Guru Joined: 20/09/2024 Location: GermanyPosts: 563 |
Hello Mixtel, this design looks really nice! It has everything to be a full featured self contained computer. Very useful. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
It's still progressing: Optional separate series resistors on GP40-GP47 GP25 now available on rear expansion connector - it can be disconnected from the LED stuff with a solder blob link Choice of different piezo sounders Optional "true" power switch link, might be useful for battery applications Optional LM4040 VREF added (but it had to be SMD to fit it in!) Added a "Standby" LED off the back contact of the power switch Quite a few track changes, some just because it was prettier. :) I'm sorting out the circuit diagram at the moment. A couple of mistakes fixed. :) It's sort of a cross between a stand-alone boot to BASIC computer and a controller with a built-in touch display. My idea is that once assembled you wouldn't need to take it to bits too often. The rear expansion connector could take I2C, RS485, multi-drop COM, HC12 or Bluetooth - or just left off. The RTC doesn't need its supplied battery - the CR2032 will keep it running for years. It's a good use for an old module, although I'd probably take the battery off a new one and solder the module in solid. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 10386 |
On holiday so not looking at the backshed much. If you made 15 I/O available in a block of 5 and an block of 10 then you could connect my Palm Pico keyboard. Also needs one extra output for the caps-lock LED. I could make the pins selection flexible and then it would be fully supported by MMBasic.  |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
I could only do that by sacrificing all the GPIO and the console. Is that a fair swap? TBH I'd prefer a wireless USB keyboard personally, but others may feel differently. Nice little keyboard though! Or, how about converting your keyboard to some sort of serial, using a RP2040-Zero? Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
A rather big set of changes today: Rotating the PGA2350 through 45 degrees to reduce most trace lengths on the board and neaten it. I rather wish I'd thought of that earlier. :) The LM4040 can now be either SOT-23 or TO92. There is now space and fixing holes for a 23mm piezo sounder. A diode across the piezo pads allows an external 5V/6V relay to be added if anyone wanted to. Well, the space was available. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| dddns Guru Joined: 20/09/2024 Location: GermanyPosts: 563 |
Hello Mixtel, nice to hear, that you further develop this project! If you are willing to release the gerber's once you are finished my plan is, to mill and build a prototype. I think this should be done as the trace length of rd,ws,rs needs to be tested to have an error free picture. I experienced problems with full standard PicoMite colours like R,G,B but a photo with RGB888 with the same setup looks good because only colours set to 255 cause these problems. On the other side I found, that once the electrical conditions are met, it runs very solid. Maybe it would be an idea, to implement the "CS combined" circuit to free one more GP and to have display's reset pin permanently high and free another GP. Maybe with a jumper. I have with your setup 17 free GP's The idea with Peter's keyboard is great and on top yours to have a 2040 being the keyboard driver which converts to PS/2 is even nicer and you have another project..to develop the firmware :) maybe a XL version in future? I think it's worth mentioning, that I think that any size of ssd1963 displays with this interface type can be driven with your board. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 8051 |
After some playing about today it now has a fixing position (2 if you leave off one USB) to mount the 4.3" version of the display. I've also added a micro SD socket with a CS link to select either/or. This can be useful if the unit is panel-mounted. I'm not going to mess with the GPIO now. TBH I don't think it's worth it. I'd much rather have 8 ADC ports and GP1 available than have the ability to add Peter's keyboard. That could be a completely different project. This design should work fine with USB keyboards, mice and game controllers. GP31 and GP25 can now be disconnected by links and used for other purposes if required. They are only operating the piezo and LED. There's not a lot that can be done with those trace lengths, they'll either work or they won't. :) Using 16 pins for the data lines restricts what you can do, particularly when GP0 and GP1 aren't available.  Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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