XMC4800 app UART DAVE calculates BRG value wrong when using 18 MBaud

[User7795]

Hi Infineon,

DAVE4.4.2 app UART calculates BRG value wrong when using Baud=18.000.000 and oversampling=8.
Using Baud=9.000.000 and oversampling=8 results in BRG=0x00001c00, which works fine, but doubling baudrate results in BRG=0xF3FF1C00, i.e. PDIV=1024, thats wrong. No initialization error occurs.

At the moment, it's not posssible to open a ticket because of maintenance.

Best Regards
Wolfgang

[jferreira]

Hi,

Thanks for reporting the issue.
In the mean time you can try with the fixes proposed below:

XMC_USIC_CH_STATUS_t XMC_USIC_CH_SetBaudrate(XMC_USIC_CH_t *const channel, uint32_t rate, uint32_t oversampling)
{
  XMC_USIC_CH_STATUS_t status;
  
  uint32_t peripheral_clock;
  
  uint32_t clock_divider;
  uint32_t clock_divider_min;

  uint32_t pdiv;
  uint32_t pdiv_int;
  uint32_t pdiv_int_min;
  
  uint32_t pdiv_frac;
  uint32_t pdiv_frac_min;

  /* The rate and peripheral clock are divided by 100 to be able to use only 32bit arithmetic */
  if ((rate >= 100U) && (oversampling != 0U))
  {
    peripheral_clock = XMC_SCU_CLOCK_GetPeripheralClockFrequency() / 100U;
    rate = rate / 100U;

    clock_divider_min = 1024U;
    pdiv_int_min = 1U;
    pdiv_frac_min = 0x3ffU;

    for(clock_divider = 1024U; clock_divider > 0U; --clock_divider)
    {
      pdiv = ((peripheral_clock * clock_divider) / (rate * oversampling));
      pdiv_int = pdiv >> 10U;
      pdiv_frac = pdiv & 0x3ffU;

      if ((pdiv_int <= 1024U) && (pdiv_frac < pdiv_frac_min))
      {
        pdiv_frac_min = pdiv_frac;
        pdiv_int_min = pdiv_int;
        clock_divider_min = clock_divider;
      }
    }

    channel->FDR = XMC_USIC_CH_BRG_CLOCK_DIVIDER_MODE_FRACTIONAL |
                   ((clock_divider_min - 1) << USIC_CH_FDR_STEP_Pos);

    channel->BRG = (channel->BRG & ~(USIC_CH_BRG_DCTQ_Msk |
                                     USIC_CH_BRG_PDIV_Msk |
                                     USIC_CH_BRG_PCTQ_Msk |
                                     USIC_CH_BRG_PPPEN_Msk)) |
                   ((oversampling - 1U) << USIC_CH_BRG_DCTQ_Pos) |
                   ((pdiv_int_min - 1U) << USIC_CH_BRG_PDIV_Pos);
                    
    status = XMC_USIC_CH_STATUS_OK;
  }
  else 
  {
    status = XMC_USIC_CH_STATUS_ERROR;
  }
  
  return status;
}

Regards,
Jesus

[User7795]

Thanks Jesus for the fast response,

it's running.

A little addition: the modifications have to be done at file
/Libraries/XMCLib/src/xmc_usic.c
(function starts at line 120)

then save the file and compile project again.

Best Regards
Wolfgang