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cs_it
cs_it
Associate II
May 16, 2026
Question

Wrong code in stm32f4xx_ll_usb.c line 2004

  • May 16, 2026
  • 3 replies
  • 118 views

Hello,

In this file, the line:

USBx_HC((uint32_t)ch_num)->HCSPLT |= USB_OTG_HCSPLT_XACTPOS_Pos;

wrongly alters bits 1 to 3 of register HCSPLT

That can be fixed simply by removing this line, since middle payload is encoded by bits 00 in the XACTPOS field.

 

    3 replies

    Pavel A.
    Pavel A.
    Super User
    May 16, 2026

    Link to the source:

    https://github.com/STMicroelectronics/stm32f4xx-hal-driver/blob/61d71646b8e8d7ff76404fbbc95f03d38bcaa938/Src/stm32f4xx_ll_usb.c#L2004

    Do you mean that these bits should not be touched after assignment to HCSPLT in line 1972 ?

     

    Exactly same code for STM32H7 , here,   here

    Exactly same code for STM32H5,  here.

    Possibly in other MCUs too.

    @mƎALLEm 

     

     

      cs_it
      cs_itAuthor
      Associate II
      May 17, 2026

      Yes, it's what I think. The coding style here is to set appropriate bits to one in the XACTPOS field, and all XACTPOS bits are zero for middle payload.

      F
      FBL
      Technical Moderator
      May 18, 2026

      Hi @cs_it 

      I assume middle payload must be encoded as 00 as described in register description fields

      An internal ticket CDM0062710   is submitted to dedicated team to report this potential bug.

      To give better visibility on the answered topics, please click on Accept as Solution on the reply which solved your issue or answered your question.Best regards,FBL
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