[GitHub] [incubator-nuttx] patacongo opened a new issue #1092: LPC17_40: UART set the buadrate jump to the Infinite loop

[GitBox <gi...@apache.org>]

patacongo opened a new issue #1092:
URL: https://github.com/apache/incubator-nuttx/issues/1092


   This was Issue 173 in the old Bitbucket repository
   
   Former user
   created an issue 2019-10-09
   
   In arch/arm/src/lpc17xx_40xx/lpc17_40_serial.c, function ioctrl:
   
       lcr = getreg32(priv->uartbase + LPC17_40_UART_LCR_OFFSET);
       up_serialout(priv, LPC17_40_UART_LCR_OFFSET, (lcr | UART_LCR_DLAB));
   
       /* Set the BAUD divisor */
   
       #ifdef LPC176x
         dl = lpc17_40_uartdl(priv->baud, priv->cclkdiv);
       #else
         dl = lpc17_40_uartdl(priv->baud);
       #endif
   
        up_serialout(priv, LPC17_40_UART_DLM_OFFSET, dl >> 8);
        up_serialout(priv, LPC17_40_UART_DLL_OFFSET, dl & 0xff);
   
       /* Clear DLAB */
   
       up_serialout(priv, LPC17_40_UART_LCR_OFFSET, lcr);
   
   the DLAB can only write during the uart reg 0x7C USR bit 0 is clear。 when the uart is busy the setting will cause the IIR[3:0] = 0111
   
   UART_16550_COMPATIBLE = NO and master has tried to write to the Line Control Register while the DW_apb_uart is busy (USR[0] is set to 1).
   


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