The new uart0 communication baud rate is inconsistent (the baud rate is reduced by 4 times)

Source: Internet
Author: User
If Keil arm is used, vpbdiv = 0x00000000 is automatically generated in startup. S, which leads to fpclk dividing by 4. The baud rate is reduced by four times. The default value of startup. s in Keil is as follows .; // <E> vpbdiv setup
; // <I> Peripheral Bus clock rate
; // <O1.0.. 1> vpbdiv: VPB clock
; // <0 => VPB clock = CPU clock/4
; // <1 => VPB clock = CPU clock
; // <2 => VPB clock = CPU clock/2
; // <O1.4.. 5> xclkdiv: xclk pin
; // <0 => xclk pin = CPU clock/4
; // <1 => xclk pin = CPU clock
; // <2 => xclk pin = CPU clock/2
; // </E>
Vpbdiv_setup equ 0vpbdiv_val equ 0x00000000 we will change it:

Vpbdiv_setup equ 1

Vpbdiv_val equ 0x00000001

Solve the problem.

  1. # Include <lpc20.x. h>
  2. # Include "config. H"
  3. # Define uart_baud (baud) (unsigned INT) (fosc * pll_m)/(baud * 16 ))
  4. Void init_uart0 (unsigned int baud)
  5. {
  6. /* Initialize the serial interface */
  7. Pinsel0 = 0x00000005;/* enable rxd0 and txd0 */
  8. U0lcr = 0x83;/* 8 bits, no parity, 1 stop bit */
  9. U0dlm = (unsigned char) (baud> 8 );
  10. U0dll = (unsigned char) baud;
  11. U0lcr = 0x03;/* dlab = 0 */
  12. }
  13. Void delay (unsigned int I) {/* Delay function */
  14. Unsigned int N;
  15. While (I> 1)
  16. {
  17. For (n = 65535; n> 1; n --);
  18. I --;
  19. }
  20. }
  21. Void sent_byte (unsigned char data)
  22. {
  23. U0thr = data; // send data
  24. While (u0lsr & 0x40) = 0); // wait for the data to be sent
  25. }
  26. Void sent_str (unsigned char const * Str)
  27. {While (1)
  28. {If (* STR = '/0') break;
  29. Sent_byte (* STR ++); // send data
  30. }
  31. }
  32. Void main (void)
  33. {
  34. Init_uart0 (uart_baud (115200 ));
  35. For (;;)
  36. {
  37. Sent_str ("www.dnp.cn/N ");
  38. Delay (200 );
  39. }
  40. }

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