Hi,
It was my mistake, before setting period PWM_Start() or PWM_Init() must have been called.
Note: PWM_Init() is called at the first time PWM_Start() is called
And in the PWM_Init(), period is overwritten to the value set in the GUI.
So I should have written
=================
PWM_Start() ;
PWM_Stop() ; /* before changing the period, PWM must be stopped */
PWM_WritePeriod(PWM_PERIOD) ;
PWM_WriteCompare(led_level) ;
PWM_Start() ;
=================
To test if PWM_WritePeriod() really works,
I made following test program.
schematic
pins
main.c
Note: To handle UART interactions I cheated by using my tty_utility
tty_utils a utility sample for CLI type program
================
#include "project.h"
#include "stdio.h"
#include "tty_utils.h"
#define PWM_PERIOD 1000 /* 65535 (0xFFFF) was too much for this purpose */
#define LED_OFF 0
#define LED_DIM 10 /* could be anywhere from 1 to 1000 */
uint16_t led_period = PWM_PERIOD ;
uint16_t led_level = LED_DIM ; /* set default to ON */
void config_pwm(uint16_t period, uint16_t compare) ;
typedef void (*func_ptr_type)(char *str) ;
void do_help(char *str) ;
void do_period(char *str) ;
void do_compare(char *str) ;
void do_pwm(char *str) ;
void do_status(char *str) ;
typedef struct _cmd_func_st {
char *cmd ;
func_ptr_type func ;
char *description ;
} cmd_func_type ;
cmd_func_type cmd_list[] = {
{ "help", do_help, "Print Help Message" },
{ "period", do_period, "Set PWM Period value, period 1000" },
{ "compare", do_compare, "Set PWM Compare value, compare 10" },
{ "pwm", do_pwm, "Set PWM Config period and compare, pwm 1000 10" },
{ "status", do_status, "Show current setting" },
{ 0, 0, 0 }
} ;
void do_help(char *str)
{
(void) str ;
int i = 0 ;
print("=== command ===\n\r") ;
for (i = 0 ; cmd_list.cmd ; i++ ) {
snprintf(str, STR_BUF_LEN, "%10s : ", cmd_list.cmd) ;
print(str) ;
print(cmd_list.description) ;
print("\n\r") ;
}
}
void do_period(char *str)
{
sscanf(str, "%*s %hd", &led_period) ;
config_pwm(led_period, led_level) ;
}
void do_compare(char *str)
{
sscanf(str, "%*s %hd", &led_level) ;
config_pwm(led_period, led_level) ;
}
void do_pwm(char *str)
{
sscanf(str, "%*s %hd %hd", &led_period, &led_level) ;
config_pwm(led_period, led_level) ;
}
void do_status(char *str)
{
uint16_t period, compare ;
period = PWM_ReadPeriod() ;
compare = PWM_ReadCompare() ;
print("=== PWM Status ===\n\r") ;
snprintf(str, STR_BUF_LEN, "Period: %hd\r\n", period) ;
print(str) ;
snprintf(str, STR_BUF_LEN, "Compare: %hd\r\n", compare) ;
print(str) ;
}
void init_hardware(void)
{
CyGlobalIntEnable; /* Enable global interrupts. */
CapSense_1_Start() ;
UART_Start() ;
tty_init() ;
splash("CapSense and LED PWM Test") ;
PWM_Start() ;
}
void config_pwm(uint16_t period, uint16_t compare)
{
PWM_Stop() ;
PWM_WritePeriod(period) ;
PWM_WriteCompare(compare) ;
PWM_Start() ;
}
func_ptr_type get_func(char *cmd)
{
int i ;
for (i = 0 ; cmd_list.cmd ; i++ ) {
if (strcmp(cmd, cmd_list.cmd) == 0) {
break ;
}
}
return( cmd_list.func ) ;
}
void do_command(char *str)
{
char command[STR_BUF_LEN+1] ;
func_ptr_type func ;
sscanf(str, "%s", command) ;
func = get_func(command) ;
if (func) {
func(str) ;
} else {
do_help(str) ;
}
}
int main(void)
{
init_hardware() ;
config_pwm(led_period, led_level) ;
prompt() ;
for(;;) {
if (get_line()) {
do_command(str) ;
prompt() ;
}
if (!CapSense_1_IsBusy()) {
CapSense_1_ProcessAllWidgets() ;
if (CapSense_1_IsSensorActive(CapSense_1_BUTTON0_WDGT_ID, CapSense_1_BUTTON0_SNS0_ID)) {
if (led_level == LED_OFF) {
led_level = LED_DIM ;
} else {
led_level = LED_OFF ;
}
PWM_WriteCompare(led_level) ;
CyDelay(500) ; /* cheap debouncing */
}
CapSense_1_ScanAllWidgets() ;
}
}
}
================
Tera Term log
When the program started, as Period = 1000, Compare = 10 and the PWM Clock = 2MHz
About 2KHz pulse(s) are generated
When I entered "pwm 2000 1000" to the prompt (>)
Now frequency is 2KHz and as compre value is 1000 the duty is 50%
When I entered "pwm 3000 1000"
The frequency was about 668Hz and duty is about 30%
When I entered "pwm 1500 1000", frequency was about 1.336 kHz
and duty is about 67%.
So the bad news is that I had a bug in my previous program,
and the good news is PWM_WritePeriod() does its work 😉
moto
