Hi,
I'm trying to set UART manually (without using mbed lib) for LPC11U24.
Pls read code below:
#include "mbed.h"
extern "C" {
extern void serial_baud(LPC_USART_Type *, unsigned int);
}
static void my_set_br(void)
{
LPC_SYSCON->UARTCLKDIV = 1;
LPC_USART->LCR |= 0x80;
// given that PCLK = 48M, baudrate = 9600
// FR_est = 1.929, divadd = 13, mul = 14, dl_est = 162
LPC_USART->DLM = 0x00000000;
LPC_USART->DLL = 0x000000a2;
LPC_USART->FDR = 0x000000ed;
LPC_USART->LCR &= ~0x80;
}
static void
my_serial_init(void)
{
LPC_SYSCON->SYSAHBCLKCTRL |= 0x1000;
LPC_IOCON->PIO0_19 &= ~0x7; // clear mode bits
LPC_IOCON->PIO0_18 &= ~0x7;
LPC_USART->FCR = 1;
LPC_USART->DLM = 0;
serial_baud(LPC_USART, 9600); // this is OK
//my_set_br(); // this is NOT OK
LPC_USART->LCR = 0x3; // set 8 bits, non-parity and 1 stop
LPC_IOCON->PIO0_19 |= 0x1; // set func to 1 and mode to 0
LPC_IOCON->PIO0_18 |= 0x1;
}
int main() {
const char *s = "Hello World!\n";
int i;
my_serial_init();
for (i = 0; i < 14; i++)
LPC_USART->THR = s[i];
while (1) ;
}
If I use mbed-lib function serial_baud to set the baudrate, then the "Hello World!" is printed to terminal perfectly.
However, if I use my_set_br to set baudrate, the "Hello World!" is printed twice.
As I understood, the official function serial_baud does nothing but set DLL/DLM/FDR. According to algo in the LPC11U24 user manual, I can caculate manually all the values:
PCLK = 48M, baudrate = 9600, FR_est = 1.929, divadd = 13, mul = 14, dl_est = 162
But why the string is printed twice with my baudrate setting?
I also noted that, if I keep the call to serial_baud, and un-comment the next line, i.e., my_set_br, the "Hello World!" is also printed once and only once.
This is a hint that my DLL/DLM/FDR values are correct, isn't it?
thanks in advance
Farrukh Hussain.
4
replies
Hi,
I'm trying to set UART manually (without using mbed lib) for LPC11U24.
Pls read code below:
#include "mbed.h" extern "C" { extern void serial_baud(LPC_USART_Type *, unsigned int); } static void my_set_br(void) { LPC_SYSCON->UARTCLKDIV = 1; LPC_USART->LCR |= 0x80; // given that PCLK = 48M, baudrate = 9600 // FR_est = 1.929, divadd = 13, mul = 14, dl_est = 162 LPC_USART->DLM = 0x00000000; LPC_USART->DLL = 0x000000a2; LPC_USART->FDR = 0x000000ed; LPC_USART->LCR &= ~0x80; } static void my_serial_init(void) { LPC_SYSCON->SYSAHBCLKCTRL |= 0x1000; LPC_IOCON->PIO0_19 &= ~0x7; // clear mode bits LPC_IOCON->PIO0_18 &= ~0x7; LPC_USART->FCR = 1; LPC_USART->DLM = 0; serial_baud(LPC_USART, 9600); // this is OK //my_set_br(); // this is NOT OK LPC_USART->LCR = 0x3; // set 8 bits, non-parity and 1 stop LPC_IOCON->PIO0_19 |= 0x1; // set func to 1 and mode to 0 LPC_IOCON->PIO0_18 |= 0x1; } int main() { const char *s = "Hello World!\n"; int i; my_serial_init(); for (i = 0; i < 14; i++) LPC_USART->THR = s[i]; while (1) ; }If I use mbed-lib function serial_baud to set the baudrate, then the "Hello World!" is printed to terminal perfectly.
However, if I use my_set_br to set baudrate, the "Hello World!" is printed twice.
As I understood, the official function serial_baud does nothing but set DLL/DLM/FDR. According to algo in the LPC11U24 user manual, I can caculate manually all the values:
PCLK = 48M, baudrate = 9600, FR_est = 1.929, divadd = 13, mul = 14, dl_est = 162
But why the string is printed twice with my baudrate setting?
I also noted that, if I keep the call to serial_baud, and un-comment the next line, i.e., my_set_br, the "Hello World!" is also printed once and only once.
This is a hint that my DLL/DLM/FDR values are correct, isn't it?
thanks in advance