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Forum Index : Microcontroller and PC projects : CMM1.5-TH - through-hole version
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
Inspired by Peter's CMM1.5, and fitting into the same case. I was wondering yesterday if it would be possible to fit a normal through-hole version in. This is what I came up with. The design isn't complete yet, it's not ready for building as without a case I can't be certain about the fit. The available drawing for that case is pretty poor. Peter used some of the normally reserved pins, which was a bit of a challenge. I've used GP25 as the SD card CS line so there's no heartbeat signal. I've connected the Pico's USB to a USB-A socket on the rear panel. That means taking the top off for installing the firmware at first - but you need to to get at the Boot button anyway. I decided that as half the GPIO connector would be rarely used I could halve it's length. I also reverted it to the original pattern on the first version of the CMM1.5 as that's the correct way up for those connectors. I don't care what you can get JLCPCB to use. :) Of course, there's no GP29, but I connected the same pin. If a modified YD-RP2040 is used then it should be possible to get GP29 back. I left out the power amp and replaced it with a LM4881 high quality headphone amp. This uses a common ground for the outputs. I added an option to power it from 5V (about 200mW max output) or 3V3 (about 90mW max output). Min. impedance is 8R so it will drive small speakers.  Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
Very nice Mick! When you can get the modules (LM4881 etc) that is a neat solution. You can even replace the SD reader with a module. What made you decide for the CH340 solution, and not the (second) pico zero that converts USB to PS2? Then you could use the proven VGA code. P.s. you could also have sacrificed GP28. The adc’s are rarely used all 3 Volhout Edited 2024-05-29 05:56 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
The CH340 is about 80p on AE and is smaller. It's also how the original CMM1.5 works and I specifically designed this to be similar. The LM45881 module is around 2 UKP by the time you've added shipping. I'm sure I found it with inclusive shipping when I got one, but I can't find it now. Getting microSD modules in can be a bit of a pain because of the depth they take up. Very often the edge of the socket is too flush to the edge of the module's PCB. Even on this design I've had to overhang the socket to get enough of the card through the front panel. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9306 |
Nice work, Mick.  The case for the CMM1.5 is even smaller then the case used for the CMM2, so there is not a whole heap of room to move on the PCB, to get everything in there. I would never had thought about a TH version - I probably would have deemed it too hard or damn near impossible unless you use SMD!  Smoke makes things work. When the smoke gets out, it stops! |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
Nice work, Mick Big fan of TH, myself. Too much happening for me to keep up with so please remind me: We can use a USB keyboard and the VGA for editing directly on the PicoMite, right? |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
Oh yeah. Using the USB version of MMBasic you can plug in a USB hub. It'll support keyboards, mice and game controllers. You load the USB MMBasic firmware in the usual way. Once running the Pico's USB is in Host mode so it can't be used as the console. A USB-TTL adapter connects a serial port on GP8/GP9 a5 115200 baud to another USB. This is the new console connection. You then plug your USB hub into the Pico's USB port. I like TH because I can still see the components even when they fall on the floor and (usually) read the numbers on them. :) ----------------------------- I'm just playing with yet another design.... :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| Amnesie Guru Joined: 30/06/2020 Location: GermanyPosts: 396 |
I like the idea of a TH-version! Nice design! Greetings Daniel |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
If people like it I'll finish it off. Beware of a few issues though: If you want the WII socket I got a couple on stupidly long delivery. I've been unable to find them anywhere apart from that one Chinese supplier. I don't think I can modify the board for a PCB edge design because of height issues in this particular enclosure. I'm tempted to change this for a RJ11 simply because of availability. It's possible to either make an adapter lead (from a WII extension lead) or chop off the WII plug and put a piece of RJ11 lead on. I *think* it will work with the YD-RP2040 nut you have to modify it by shorting out two diode pins. If it will work then you get GP29 back and 16MB of flash. There is a problem in connecting to the USB on this board though, which may need some sort of butchered connector. The LM4881 module and the CH9340C module are both available from AliExpress. The LM4881 may cost a little more than you first expect though due to postage charges. The GPIO connector isn't compatible with the current version of the CMM1.5. The audio should drive sensitive speakers ok, but 200mW per channel isn't a lot. It would be ok for a quiet room but don't expect loud bangs and crashes from games. It's more than enough for headphones up to 64R though. You'd be surprised how loud 1W is, and 200mW isn't 1/5th as loud as 1W. It's a lot more. ---------------------- @Grogster I added a WII connector just to rub it in. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
Absolutely and I was reading something related to industrial controls and the bottom-line was that TH was more resilient "with SMD, solder is merely a conductive adhesive" (paraphrased). |
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