rpdom wrote: ↑
Mon Jul 29, 2019 5:59 am
USB power on the Pi 2B is disabled until the Pi has started to boot, so that's not the problem.
Have you been through the "Not Booting" Sticky post in troubleshooting? (Which is probably where this post should be moved to).
Hi yes I have - basically both LED's on = SD card not found.
My SD card and PSU both work perfectly on another Pi.
That thread did mention this however:
"Booting on a Pi is multi-phased: the majority of the boot process is executed by a small dedicated processing unit (CPU) inside the VideoCore GPU and consist of several stages. The Broadcom SoC contains a very small permanent memory which obtains the code to boot the device. First, it uses simple USB code to try to read a file pushed to it through the USB hardware. If this is unsuccessful, the code aborts, and uses its MMC hardware to attempt to read a file from a MMC compatible device. On the Pi, this is the SD card; the file should be on a FAT16 or FAT32-compatible filing system, and is called bootcode.bin. "
I have not tried USB boot yet - Does anyone know anything more about the 'simple USB code to try to read a file pushed to it through the USB hardware' method? This is the first time I've heard of this.
jbeale wrote: ↑
Mon Jul 29, 2019 6:02 am
I just totally changed my reply, because I believe the photo of the board in the test point link you provide may be a R-Pi 3 (?)
Just be sure which model Pi you are trying to use; by now I have forgotten how many different Pi varieties there are. I checked one under my desk that I thought at first was a Pi 2 but is in fact a B+ V1.2 which does have the numbered test points on the back (unlike the original Pi B which had no test points). On the B+ v1.2 board PP27 exists, but it is simply connected to GPIO21 (physical pin 40, at the bottom outside edge of the GPIO pins) and that is clearly not USB power. Unless you program it differently I would expect that test point on the B+ v1.2 board to be 0 V at bootup.
Interesting I was under the impression that all full size Pi's with 40 pin GPIO's use the same PP test points, from the link I posted.
'Below is a list of test points which can be found on Raspberry Pi 2, 3 and some are also on b+.'
However it's just a random site so not guarenteed to be correct - I'd be interested to know of the other PP test points for the other boards.
On my board is says 'Raspberry Pi 2 Model v1.1' so I think it's one of the earlier Pi 2's, and PP27 seems to be connected to the USB 5V pins.
Thanks for putting it in the right section. Looks like I have a RPi 2B a10141.
I've gone thru the boot problem sticky and tried everything apart from somehow booting using USB instead of SD card, but there are no instructions on how this is done in the thread.
There is no USB power when powered up on the Pi, I found a USB lamp thing for testing so I'm not even sure the USB boot method would work here without USB power on the Pi's pins.