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Forum Index : Microcontroller and PC projects : 2040 power supply.

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Tinine
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Joined: 30/03/2016
Location: United Kingdom
Posts: 1646
Posted: 03:08pm 22 May 2022
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So I have an external 3.3v supply to my PGA-2040.
For the console connection, I use a USB cable from the PC but no USB connector on the PGA-2040 (I have a more rugged alternative).

Am I good to use just the two data signals and ground on the USB connection?

Craig.
 
Mixtel90

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Joined: 05/10/2019
Location: United Kingdom
Posts: 8300
Posted: 03:22pm 22 May 2022
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Have you checked the circuit of the Pico? It would be a good guide. On there they are connected to the RP2040 via 27R 1% 0603 resistors.

As far as the supply goes, it's probably not good to have signals on the data pins without power to the RP2040. Could you diode your external supply and the USB supply?
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
Tinine
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Joined: 30/03/2016
Location: United Kingdom
Posts: 1646
Posted: 03:43pm 22 May 2022
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  Mixtel90 said  Have you checked the circuit of the Pico? It would be a good guide. On there they are connected to the RP2040 via 27R 1% 0603 resistors.

As far as the supply goes, it's probably not good to have signals on the data pins without power to the RP2040. Could you diode your external supply and the USB supply?


Oh there will always be a 3.3v supply directly to the RP2040. I just want to disable the the on-board buck-booster and still be able to talk USB.
 
Mixtel90

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Posted: 05:15pm 22 May 2022
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As long as it has a supply it doesn't matter where it comes from. It might be ok anyway, but better safe than sorry. All it really needs is a schottky diode from the usb input to the 5V rail. That protects the usb host and makes sure the RP2040 is powered if the main 5V supply to your regulator is off. Assuming you are using a regulator of some sort. :)
Edited 2022-05-23 03:18 by Mixtel90
Mick

Zilog Inside! nascom.info for Nascom & Gemini
Preliminary MMBasic docs & my PCB designs
 
Tinine
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Joined: 30/03/2016
Location: United Kingdom
Posts: 1646
Posted: 11:15am 24 May 2022
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Can't make sense of this  

Supplied by USB 5v and 3V3_EN not tied to ground....No problem.
Tie the 3V3_EN to ground and with-or-without external 3V3, the USB port is no-longer recognised  

Craig


Edited 2022-05-24 21:17 by Tinine
 
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