Stm32 usb and hsi - not sure what is wrong.

CaptainJL · ‎2023-06-30

Hey all,
I am wondering if anyone has some insight into why i cannot get a usb connection working (trying as HID).
I can power up and debug the MCU (STM32F103RBT6), but cannot get the USB to connect.

For the HSI I am using 10pF for C1 and C2, and a 1000 ohm resistor for Rext (Rosc). My oscillator is the 7M16000024 (16Mhz, 10pF load capacitance according to https://www.digikey.com/en/products/detail/txc-corporation/7M16000024/5954370 )

I have been following https://www.youtube.com/watch?v=tj1_hsQ5PR0&t=877 to get a USB connection happening (which fails to connect).
Some images below show the circuit and i hope are useful.

AScha.3 · ‎2023-06-30

as gbm said: you need a 1.5 kohm pullup to 3v3 , to start enumeration as device on usb .

and maybe - damping resistors in data lines, 22...27 ohm.

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View solution in original post

gbm · ‎2023-06-30

1. Use the debugger to check if HSE has initialized correctly (osc status).

2, Make sure that you have a 1.5 pull-up resistor on DP.

My STM32 stuff on github - compact USB device stack and more: https://github.com/gbm-ii/gbmUSBdevice

AScha.3 · ‎2023-06-30

as gbm said: you need a 1.5 kohm pullup to 3v3 , to start enumeration as device on usb .

and maybe - damping resistors in data lines, 22...27 ohm.

If you feel a post has answered your question, please click "Accept as Solution".

CaptainJL · ‎2023-07-01

Ah thanks guys. The 1.5k pullup on DP fixed it!