Unresponsive Pico

Hi, I think I might have broke the pico I received a few days ago.
I was attaching the pico to unsoldered wires on GND and VCC (or was it 3v?) and an error messaged appeared on my macbookair saying that usb was drawing too much power and it did something about it (i didn't look, as it was very similar to another error I receive often with my prettymuch constantly attached SDcard randomly disconnecting), and after that the pico does not seem to react on inserting (that quick red led blink) nor showing up on serial port.

Holding down the button on trying to go into bootloader does not respond either.

I've tried rebooting to no vail.

suggestions?

1) Does the USB port still work? You may need to shutdown + restart it to make it reappear again.
2) Does the Pico work in a USB port on another computer?

It sounds like you slipped when connecting wires and shorted together two of the power pins (or you connected something that was shorted). How much damage that did remains to be seen (I'm pretty sure I've briefly shorted one of my picos - power to ground - and it did the same thing as the original board did, ie, make the USB port non-functional until system restart, but otherwise not impact anything).

I believe it's totally dead then, the usb port on the computer is still working fine, I've rebooted the computer twice and tried again, but to no vail. I recently tried it on another computer, without software, didn't do it's normal blinky routine.

Damn!

With it plugged into USB, measure voltage between ground and VBat. It should be 4.7ish. If it is, measure 3v3 (3.3v). It should be 3.3ish.

I predict one or both of those will be 0. If VBat is 0 with it plugged into USB, check voltage on the diode closest to the USB connector, on the side closer to the BAT_IN pin. That will almost certainly give you 5v, indicating that the diode is an open circuit. The schottky diode on the USB supply often is the weakest link (in general, not specific to Espruino - this seems to happen a lot on the Arduino forums)

If you have the 4.7, but no 3.3, the regulator was what you fried.

The regulator actually has automatic shutdown, so it's almost certainly the diode that's blown (I'd check as @DrAzzy says to make sure though).

If that's the case then you have a few options:

• Replace the diode (any diode will do to get it to work, and they're cheap!)
  
• Short out the diode - potentially easy, but it'll mean you won't be able to power the Espruino from batteries any more. Also if you short the board out with it shorted, something else will end up getting hot!
  
• Replace the diode with a PPTC (self-resetting) fuse. Again, you won't be able to use batteries, but it will at least save you from future problems
  
• Or if you don't want to do any soldering you should still be able to power your board by putting a 5V supply between GND and VCC/5V pins
  

just to be sure, you're talking about the diode labeled S4?
I also measured the GND and VCC/3v3, it had something like 1.8v, and not 0 as suggested here.

Yes, S4 is the one. If GND to VCC is 1.8v then the diode is almost certainly the problem (unless you still have something connected to the board that could be drawing too much power from it?).