@bagfalls: Hittade detta på nätet när elektroniktyper på hackaday diskuterade RPi4
- och de hade speciellt haft problem med Pi3 B+, så det är inte så att du valt fel nätadapter utan du kanske bara haft otur med just din modell.
I did voltage measurements of RasPi 3 bus for a client and found that the voltage drop through the micro USB port put the bus voltage perilously close to the brownout voltage. During boot the bus voltage would sag enough to cause memory card read errors.
After lots of hardware debugging we decided it was the USB port and associated circuitry on the board – ie, the cable and supply were not the source of the problem. We also decided that the onboard capacitors were probably a little small as well.
For development I now power all my boards through the I/O connector and add a big electrolytic on the 5v and 3.3v rails.
This is why RasPi 3 supplies sold online have a 5.25 volt output.
benemorius says:
June 24, 2019 at 10:03 am
I arrived at the same conclusion – if you put only 5 volts at the usb port, you won’t be getting enough voltage on the other side of it under load.