2025-07-16 11:55 PM - edited 2025-07-17 12:01 AM
We have a STM32070CBT6 with minimal connections (schematic below) and it appears to be unresponsive to USB enumeration, although it does pull DP low to trigger it. This occurs when hotplugging it or holding reset low for a few seconds. I've checked the input on PF0 and it is getting a clean 16 MHz.
2025-07-17 12:13 AM
On the host side do you see enumeration error or nothing at all? Borrow a hardware USB analyzer.
2025-07-17 12:46 AM
[ 3969.049330] usb 1-1.1: new full-speed USB device number 91 using xhci_hcd
[ 3969.049669] usb 1-1.1: Device not responding to setup address.
[ 3969.253544] usb 1-1.1: Device not responding to setup address.
[ 3969.457301] usb 1-1.1: device not accepting address 91, error -71
[ 3969.457668] usb 1-1.1: WARN: invalid context state for evaluate context command.
[ 3969.457853] usb 1-1-port1: unable to enumerate USB device
With a scope I see the pull down and then the setup packets going through every address from the host but no response from the STM32.
2025-07-17 12:50 AM
You can decode the packet if you like, but I've tried on multiple machines so I doubt this is a USB driver issue. None of the packets are longer than this so I assume they're all setup packets.
2025-07-17 12:59 AM - edited 2025-07-17 1:04 AM
I've also tried another board without an oscillator installed. In this case the pull-down does not occur, so it is not the case that it's just not detecting the oscillator. The MCU is certainly reaching the USB configuration step but then it is just not responding to USB setup packets.
For the sake of completeness I also installed the oscillator on that board, in which case it behaves just like the first one.
2025-07-17 3:32 AM
Hi @liampwll
Would you insert a USB hub?
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2025-07-17 3:37 AM
I tried with a short cable going to a USB port with a hub close by. I should also note that we have practically the exact same board with a STM32F070F6P6 and USB works fine on there. I can not test if the bootloader USB works on that board as the F6 does not switch the shared pins to USB mode.
2025-07-18 2:00 AM
I've also soldered a UART adaptor that is known to work on our F6 variant to pins PA9 and PA10, the same ones we use for programming our F6 variant. In this case when the BOOT0 jumper is installed PA9 is pulled high as you'd expect but the device does not respond to USART messages. I've tried this with the oscillator installed and removed. I'm led to question if the bootloader on this particular model is actually functional at all.