serial_baudrate_dividers - Program to dump out dividers for a UART, after it…

Users » simon » Code » serial_baudrate_dividers

Program to dump out dividers for a UART, after it being set up

main.cpp@0:9343a4c09e4d, 2010-10-13 (annotated)

User	Revision	Line number	New contents of line
simon	0:9343a4c09e4d	1	#include "mbed.h"
simon	0:9343a4c09e4d	2
simon	0:9343a4c09e4d	3	DigitalOut myled(LED1);
simon	0:9343a4c09e4d	4
simon	0:9343a4c09e4d	5	Serial s(p9, p10);
simon	0:9343a4c09e4d	6
simon	0:9343a4c09e4d	7	int main() {
simon	0:9343a4c09e4d	8
simon	0:9343a4c09e4d	9	// setup the baudrate to 4800
simon	0:9343a4c09e4d	10	s.baud(4800);
simon	0:9343a4c09e4d	11
simon	0:9343a4c09e4d	12	// extract the resulting divider values that were setup
simon	0:9343a4c09e4d	13
simon	0:9343a4c09e4d	14	LPC_UART3->LCR \|= (1 << 7); // set LCR[DLAB] to get access to dividers
simon	0:9343a4c09e4d	15	int dlm = LPC_UART3->DLM;
simon	0:9343a4c09e4d	16	int dll = LPC_UART3->DLL;
simon	0:9343a4c09e4d	17	int div = LPC_UART3->FDR & 0xF;
simon	0:9343a4c09e4d	18	int mul = LPC_UART3->FDR >> 4;
simon	0:9343a4c09e4d	19	LPC_UART3->LCR &= ~(1 << 7); // clear LCR[DLAB]
simon	0:9343a4c09e4d	20
simon	0:9343a4c09e4d	21	int pclk = 96000000;
simon	0:9343a4c09e4d	22
simon	0:9343a4c09e4d	23	// from LPC1768 User Manual, 14.4.12 :
simon	0:9343a4c09e4d	24	float baudrate = pclk / (16.0 * (float)(256 * dlm + dll) * (1.0 + ((float)div / (float)mul)));
simon	0:9343a4c09e4d	25
simon	0:9343a4c09e4d	26	printf("dlm = %d, dll = %d, div = %d, mul = %d\n", dlm, dll, div, mul);
simon	0:9343a4c09e4d	27	printf("baudrate = %f\n", baudrate);
simon	0:9343a4c09e4d	28	}