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Forum Index : Microcontroller and PC projects : Raspberry Pi-coMite
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
Yes, I've been playing again. Having taken a swipe at Arduino with the ArdoMite, I thought I'd have a go at Raspberry Pi too, since they got me into all this. :) Hence:  I'm still playing with this. The board size and fixings are bang on. Generally all IO is, at least, in the right places even if it's the wrong shape. It might be possible to modify the "layered plastic sheets" cases to take this by trimming holes bigger. There's not enough IO on the PicoMite to fill the 28-pin connector and I've taken a liberty or two, but by and large it isn't too bad. Power pins, grond pins, serial port and a SPI port are in the right place but the SPI only has one CS pin. At the moment the other SPI is missing, but I might parallel the SD card one onto it if I can. Just at the moment I wouldn't regard it as buildable because I haven't debugged it much. 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: 4256 |
Mick, Put gp14 and gp15 at the same pins as the pi has for i2c. So you can use shields/hats... Volhout Edited 2023-03-16 23:16 by Volhout PicomiteVGA PETSCII ROBOTS |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
I don't think there is I2C on the 26-pin connector. It's on pins 27 and 28 of the bigger one. I said 28 pins above, sorry. None of them have 28 pins. :) Edit: OOPS! It looks like it's on 3 and 5 (looking at a different drawing). Edited 2023-03-16 23:30 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| pwillard Senior Member  Joined: 07/06/2022 Location: United StatesPosts: 292 |
Glad you caught it. I was pretty certain that my tiny PI QWIIC adapter only needed a few of the lowest-numbered pins. |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
GPIO pinout is now: 3V3 P0WER 1 - 2 5V POWER I2C SDA GP4 3 - 4 5V POWER I2C SCL GP5 5 - 6 GND GP27 SD MOSI 7 - 8 COM1 TX GP0 GND 9 - 10 COM1 RX GP1 GP26 SD SCLK 11 - 12 NC GP28 SD MISO 13 - 14 GND GP2 15 - 16 GP3 3V3 POWER 17 - 18 GP13 SPI2 MOSI GP11 19 - 20 GND SPI2 MISO GP12 21 - 22 NC SPI2 SCK GP10 23 - 24 SPI2 CS0 GP15 GND 25 - 26 SPI2 CS1 GP14 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: 6814 |
This is getting fun. :) If you aren't interested in the uSD card (and it's not essential) you now have GP22 and all three ADC inputs available (eat your heart out, Raspberry Pi :) ). Note that the "tiny" RTC module is right at home here, it plugs directly onto pins 1,3,5,7,9 of the GPIO. GPIO changes: 3V3 P0WER 1 - 2 5V POWER I2C SDA GP4 3 - 4 5V POWER I2C SCL GP5 5 - 6 GND GP27 SD MOSI 7 - 8 COM1 TX GP0 GND 9 - 10 COM1 RX GP1 GP26 SD SCLK 11 - 12 SD CS GP22 GP28 SD MISO 13 - 14 GND GP2 15 - 16 GP3 3V3 POWER 17 - 18 GP13 SPI2 MOSI GP11 19 - 20 GND SPI2 MISO GP12 21 - 22 GP6 SPI2 SCK GP10 23 - 24 SPI2 CS0 GP15 GND 25 - 26 SPI2 CS1 GP14 You can now build this as a "headless" board, omitting the video resistors and/or PS2 keyboard components. In this case the GPIO header can be expanded to the full 40 pins: RESERVED 27 - 28 RESERVED GP16 29 - 30 GND GP18 31 - 32 GP17 GP19 33 - 34 GND GP21 35 - 36 GP20 GP9 37 - 38 GP8 GND 39 - 40 GP7 Note that it's also possible to leave off the audio stuff, but one pin is on the shortened header and the other is on the full one. Still useful though if you want maximum IO. Edited 2023-03-18 20:51 by Mixtel90 Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3816 |
Just checking - not quite at the stage of sending off to get PCBs yet? John |
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| matherp Guru Joined: 11/12/2012 Location: United KingdomPosts: 9139 |
Just FYI, I designed Pi format boards for the MM2, MM+ and MMX including a Pi-Zero format MM2. Take-up -zero. Search the board if interested |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
Probably not far off now, John. I'm not sure if I can squeeze much more outt of it. :) Thanks Peter, I'll have a look. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3816 |
I've just realised that the large footprint bottom left may not be what I guessed. What is meant to plug in there? John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
Bottom left? The PicoMite? Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Hans Senior Member Joined: 18/10/2022 Location: CanadaPosts: 116 |
@Mixtel90 When ready, I would certainly take one of these! Hans ...  |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
Getting nearer. Just a final bit of checking, I think. It seems to be OK (famous last words).  And we now have a circuit. Raspberry Pi-coMite circuit.pdf Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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NPHighview Senior Member Joined: 02/09/2020 Location: United StatesPosts: 200 |
Hi, Mick - are R3 and R4 47kohm? The PDF shows them as 4k7... Live in the Future. It's Just Starting Now! |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
Most people probably won't need them. 4k7 is a guesstimate and will depend on the amplifier. In theory they just load the output a bit - I hadn't got room for a series resistor to form a potential divider. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3816 |
Yes. I thought it was that but the naming Pi-... made me wonder if it was a Pi not a Pico. John |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6814 |
It's Pi-sized, with Pi-compatible fixings and more-or-less-Pi-compatible GPIO. :) Hopefully the latest pic makes more sense. I've turned it round because a real Pi has the lettering arranged like that. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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