How do i use the standalone USB (CN11) for Discovery board B-L072Z-LRWAN1?

[JWieb]

I am trying to use the standalone USB (CN11) for Discovery board B-L072Z-LRWAN1. But nothing seems to be happening. I have shorted the two jumper SB16 and SB15 and measured a solid 3.3v on VDD_USB_LRA and VDD_MCU_LRA. The USB lines dont seem to waiver at all from 0v.

My intent is to use the onboard bootloader (with BOOT0 HIGH) for programming.

This question was answered before but there isn't much of an answer.

https://community.st.com/s/question/0D50X00009XkWODSA3/bl072zlrwan1-cn11-usb-conn-device-mode

[Tesla DeLorean]

@Community member​ has had a USB CDC running from the Murata part, I believe he used CubeMX to bring up the port.

For the system boot-loader, I'd perhaps check the OSC_IN source (SB13 ?)

Perhaps port

STM32Cube_FW_L0_V1.11.2\Projects\STM32L073Z-EVAL\Applications\USB_Device\CDC_Standalone

[JWieb]

I figured it out. There is another solder bridge SB37 that needs to be cut. This connects the target MCU RESET to the ST-link RESET so without powering the ST-link the reset line gets pulled low.

Why wasnt this a regular jumper?!

Thanks for the help!

[xarion]

Hello @JWieb​ Just wondering what firmware you used, did it enumerate a serial port?

[Tesla DeLorean]

Yes, it can come up as a VCP/CDC, there isn't a stock firmware.

You'd basically have to make a generic STM32L0 CDC, perhaps look at the examples for the EVAL series boards, or have CubeMX generate some boiler-plate code, and then merge that into a LoRa project.

Figure several hours to get something clean and workable.