I've a custom L476 board (battery powered,MSI 48MHz system clock, no HSE, no PLL) to implement USB MSC (OTG-FS). I'm using L4 Nucleo ST link extender to upload code on my Custom board. I've noticed that, when the custom board is connected with Nucleo with ST link, USB recognition has always been successful. But when I remove ST link debugger cables from my custom board and reconnect battery (to emulate power on reset), USB does not recognize at all. Code 43 error: Device Description Request Failure. I tried USB VCP code. It also works only when ST link debugger connected.
What could be the solution? My schematic is as follows.
I've put vbus_sensing_enable =0 and using PA9 as a GPIO EXTI interrupt to change USB states (from VCP to MSC) and staying in USB mode as long as USB available using: while(LL_GPIO_IsInputPinSet(GPIOA,LL_GPIO_PIN_9));
Also I put USB_ID pin in internal Pull Up configuration.
I have a 1k Pull up resistor on board. To test, I replaced with 1.5K on another board, but its the same issue.
I request your kind guidance to solve this issue.
Thanks in advance.