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> eMMC boot pin jumper, picture via [Jeff Geerling][2]
### The issue
I prepared the board with a jumper, micro USB cable and installed
the `rpiboot` tool, all as [per the official documentation][5].
But when I powered on the board, no USB device showed up. The
tool kept hanging on `Waiting for BCM2835/6/7/2711...`.
The strange thing however was that the cm4 module booted up fine,
I saw Raspbian on my HDMI display, network was available and I
could `ssh` into the cm4 just fine. Only when I tried to flash
the storage it failed. The red 'D1' LED turned on, no green ACT led,
but no USB device shows up.
Sometimes I did get `dmesg` logs on Linux, but they were full of errors:
usb 1-5: new full-speed USB device number 17 using xhci_hcd
usb 1-5: Device not responding to setup address.
usb 1-5: Device not accepting address 8, error -71
usb 1-5: device descriptor read/64, error -71
usb usb1-port5: unable to enumerate USB device
usb usb1-port5: attempt power cycle
I didn't always get log errors like this, sometimes nothing happened.
* I tried a different power supply (12v, 2A) but that didn't help. Board
booted just fine, but no USB flashing.
* I tried a few different Micro USB cables.
* I tried a Windows PC. Installed drivers, but no storage / usb appeared.
* Tried a USB 2.0 port as opposed to a USB 3 port.
* Tried a different Linux version (Debian vs. Arch)
I found [this topic][5] on the Raspberry Pi forums where they received a
broken module, a new one (swapped by Farnell) worked just fine. I was running
out of options to try, so I was on the brink of requesting a waranty swap of
my module.
The weirdest part was that the cm4 worked just fine in normal mode, Raspbian
showed no errors, everything worked, except for the eMMC flashing.
### The solution
**The cm4 was not mounted correctly in the I/O board, it was screwed in too tight.**
I used m2.5 standoffs to screw the compute module into the I/O board. These
were so tight, that the compute module was not flat, but a bit convex. Not a
lot, but still visibly convex (not flat).
I'm used to screwing in modules, as at work we also have a SOM module that
does require tight screws. That is a SO-DIMM socket however, the compute
module 4 has two high-speed, high-density 100-pin mezzanine connectors.
I saw a video of Jeff where he just clicked in the cm4, no
screwing whatsoever, so I took a closer look at my module, and decided to try
it without screws.
After removing the screws and re-seating the board (just a click, no screws),
the issues went away and I can now flash the board as intended with `rpiboot`:
$ sudo ./rpiboot
RPIBOOT: build-date Feb 22 2022 version 20220208~181027 042cd145
Waiting for BCM2835/6/7/2711...
Loading embedded: bootcode4.bin
Sending bootcode.bin
Successful read 4 bytes
Waiting for BCM2835/6/7/2711...
Loading embedded: bootcode4.bin
Second stage boot server
Loading embedded: start4.elf
File read: start4.elf
Second stage boot server done
This is `dmesg` output when everything is working correctly:
usb 3-1.2: new high-speed USB device number 34 using xhci_hcd
usb 3-1.2: New USB device found, idVendor=0a5c, idProduct=0001, bcdDevice= 0.01
usb 3-1.2: New USB device strings: Mfr=2, Product=1, SerialNumber=3
usb 3-1.2: Product: Compute Module
usb 3-1.2: Manufacturer: Raspberry Pi
usb 3-1.2: SerialNumber: xxxxxxxx
usb-storage 3-1.2:1.0: USB Mass Storage device detected
scsi host4: usb-storage 3-1.2:1.0
scsi 4:0:0:0: Direct-Access RPi-MSD- 0001 PQ: 0 ANSI: 2
So make sure your cm4 module is not screwed in tightly. It should be flat in the I/O
board, not convex.
Here's a photo of my cm4 after the [bootloader update was successful][7]:
![green screen][6]
[1]: /s/inc/img/j2-emmc-jumper.jpeg
[2]: https://web.archive.org/web/20220226203155/https://www.jeffgeerling.com/blog/2020/how-flash-raspberry-pi-os-compute-module-4-emmc-usbboot
[3]: https://github.com/raspberrypi/usbboot
[4]: https://web.archive.org/web/20220223025655/https://www.raspberrypi.com/documentation/computers/compute-module.html#setting-up-the-cmio-board
[5]: https://web.archive.org/web/20220226205117/https://forums.raspberrypi.com/viewtopic.php?t=82905
[6]: /s/inc/img/cm4-green-bootloader.jpg
[7]: https://web.archive.org/web/20220226205626/https://www.jeffgeerling.com/blog/2022/how-update-raspberry-pi-compute-module-4-bootloader-eeprom
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