Diode de-soldering?

[rlafuente]

Hi, thank you for an amazing project! I was looking into ways to control the Frekvens and only knew about Frumperino's arduino efforts.

I'm about to hook this up according to your instructions, but wanted to doublecheck this detail:

If USB connection is used, one must de-solder diode that are between VUSB and VSYS from Pico PCB.

I searched online about this and all indications are that the diode is necessary to not fry the host USB machine. I'm very sure you know what you are doing, but ruining my laptop (and/or my Frekvens) is a tough prospect :-)

To be sure, is this the right one to take off?

And is there any security caution I should take with the Pico after removing the diode?

Thank you in advance!

[ah01]

Hi,

Short answer:

Yes. That is the diode you should remove.

Long answer:

Diode D1 is there for multiple purpose. Mainly to ORing external power supply (connected on VSYS pin) and from USB with priority on VSYS. Also it will protect USB host from back-feeding from VSYS.

But in case of this ikea box, original power supply has 4.5 V. So this diode will be always on (VUSB is 5V) when USB is connected. So device will be powered from USB and now is the question how the 4.5 V power supply will behave when you feed 5V to its output... will it work, will magic smoke escape. I prefer not to try this and remove D1 ;)

(picture from datasheet, chapter 4.4)

[rlafuente]

I'm really grateful for your reply -- thank you!

I went ahead, and I think I blew my Frekvens in the process since I had previously connected another RPico with the diode on. It's been a long while since I picked up a hardware project so I'm okay with the loss :) A few new cubes arrived today and I'll give this another shot.

I'm super eager to get this to work and write some graphics experiments. It's great to have an alternative to the arduino route, so thank you again for publishing these steps, and being around to clear things up :)

[jpe2ch]

I am wondering: would adding a diode into the feed from the Frekvens power to VSYS not work as well? This would prevent any current from VBUS into the Frekvens power supply, avoid soldering on the PI Pico and still keep some level of protection of the USB. Any educated guess?

[jpe2ch]

I had some time at hand this weekend and checked the documentation: the RPI Pico manual describes using multiple power sources by adding a Schottky diode to each supply. I did not have a Schottky diode at hand and just used a normal one which I found lying around. Works flawlessly. Thanks for the Micropython code, this was good to have as a starting point for tinkering.