Hello Community!
I have worked in several version of a RP2040 custom board and I have not success making it work. This is a RP2040 powered through a CR2032 coin cell (3V). The problem I have is that, in datasheet: “USB_VDD supplies the chip’s USB PHY, and should be powered at a nominal 3.3V. To reduce the number of external power supplies, USB_VDD can use the same power source as the digital IO supply (IOVDD), assuming IOVDD is also powered at 3.3V. If IOVDD is not powered at 3.3V, a separate 3.3V supply will be required for the USB PHY“.
This suggest that USB_VDD doesn’t be wired directly to USB 5V. In the other hand, I have not a 3V3V LDO, since my nominal voltage will be always less or equal to 3V. I tried not connecting the 5V form USB, but didn’t worked the UCB communication. Now I don’t know if I can wire together USB_VDD and USB voltage or not. Any suggestion?
Hi there, Fabian,
I’ve moved this post to its own thread as it felt like enough of a thematic change that it deserved its own thread.
Fabian, I’m not sure if your idea is tenable in practice. You should never tie USB_VDD to the 5 V from the USB, you will fry the chip’s PHY which can accept a maximum voltage of at most 3.6V.
If you are wanting a working USB you must generate a ~3.3 V rail from USB VBUS (or another regulator) and feed it to both IOVDD and USB_VDD.
A CR2032 at 3 V just isn’t sufficient to support USB connections unfortunately.
Hi Fabian,
Welcome to the forum!!
The battery might also not be able to supply enough wattage to the RP2040 to let it power up.
Could you please provide some more info about your board? A screenshot of the schematic and board layout should help.
PS: This video has been making the rounds in my algorithm, a worthwhile watch for any low-power MCU projects: https://youtu.be/TGbtzlWb-Kc?si=teAf-b5S4LsHGFCJ
Liam
