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Forum Index : Microcontroller and PC projects : PicoMite USB versions - power advice please
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6787 |
I'm playing with a(nother) design for the PicoGAME 4. As the system is powered by the USB-C converter, is it advisable to put a switch in the 5V rail from here? It would mean that with the Pico powered off the USB-TTL converter would probably still be putting out 3V3 (at limited current) to GP8 / GP9. I'm not happy with this at all. You get the same problem if you switch off the 3V3 by shutting down the switching supply using 3V3EN. The only safe way to power off is to pull the USB-C plug. 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 |
Hi, there are USB C connectors with a built in switch. May this solve your problem? Otherwise I see no solution for this. Edit: Since you design your own board, why not just putting a switch right after the USB C connector? Greetings Daniel Edited 2024-02-18 06:56 by Amnesie |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6787 |
I'm intending to use a USB-C to TTL converter module - I doubt if I can solder a USB-C socket. I can switch the 5V coming from it, but the chip is already powered by that stage and the TTL lines will be pulled up. That will attempt to power the Pico via the ESD protection diodes if it's not powered up. It probably wouldn't be dangerous to the chip if the pullups have a high enough value, but it may prevent it from booting up normally. If I can't think of something I'll just leave it to the user to either unplug the USB lead or switch it off. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
what's wrong with usb to usb converter and ttl to usb sir?  |
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| aFox Regular Member  Joined: 28/02/2023 Location: GermanyPosts: 76 |
This could make the NSA suspicious. |
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TassyJim Guru Joined: 07/08/2011 Location: AustraliaPosts: 6098 |
Put a 1k resistor in each of the signal lines between the USB/TTL and the pico. Then measure the voltage with 5V off. I don't think there will be much to worry about. I might even try it later today but some house-work first. If you don't like that idea, make the power switch double pole and switch the pico Rx line as well as power. Jim Edited 2024-02-18 14:15 by TassyJim VK7JH MMedit MMBasic Help |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6787 |
Thanks for the ideas, folks. :) Stan: I want it all mounted on the PCB, in one of those nice Hammond cases that I've used for the other PicoGAME boards. I can't fit one of those long CP2102 boards in. Jim: That sounds like a sensible idea. I might allow for those resistors anyway. To anyone thinking of using those tiny USB-C to TTL converter boards - Note that the 5V and GND are reversed between the 2102 and 340 types! Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
I want to mount the usb to ttl horizontal on strip board. don't think desoldering pins and replacing easy, maybe straighten them and mount upside down or remove the plastic joining the pins and bend them 90deg |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6787 |
These, Stan. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| stanleyella Guru Joined: 25/06/2022 Location: United KingdomPosts: 2129 |
Thanks Mick, more sensible for vero. |
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