djsundog/circuitpython
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

esp8266/esppwm: Fix PWM glitch when setting duty on different channel.

Browse Source 
The PWM driver uses a double buffer for the PWM timing array, one in
current use and the other one to update when changing duty parameters.
The issue was that once the duty parameters were changed the updated buffer
was applied immediately without synchronising to the start of the PWM
period.  By moving the buffer toggling/swapping to the interrupt when the
cycle is done there are no more glitches.
This commit is contained in:
Olivier Ortigues 2020-04-22 13:57:54 +02:00 committed by Damien George
parent cae77daf00
commit e32302c1a6
1 changed files with 18 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

26
ports/esp8266/esppwm.c
View File

@ -57,6 +57,7 @@ STATIC uint8_t pwm_timer_down = 1;
STATIC uint8_t pwm_current_channel = 0;
STATIC uint16_t pwm_gpio = 0;
STATIC uint8_t pwm_channel_num = 0;
STATIC volatile uint8_t pwm_toggle_request = 0;
// XXX: 0xffffffff/(80000000/16)=35A
#define US_TO_RTC_TIMER_TICKS(t) \
@ -126,6 +127,9 @@ pwm_start(void) {
LOCK_PWM(critical); // enter critical
// if a toggle is pending, we reset it since we're changing the settings again
pwm_toggle_request = 0;
struct pwm_single_param *local_single = pwm_single_toggle[pwm_toggle ^ 0x01];
uint8 *local_channel = &pwm_channel_toggle[pwm_toggle ^ 0x01];
@ -188,14 +192,14 @@ pwm_start(void) {
// start
gpio_output_set(local_single[0].gpio_set, local_single[0].gpio_clear, pwm_gpio, 0);
// do the first toggle because timer has to have a valid set to do it's job
pwm_toggle ^= 0x01;
pwm_timer_down = 0;
RTC_REG_WRITE(FRC1_LOAD_ADDRESS, local_single[0].h_time);
}
if (pwm_toggle == 1) {
pwm_toggle = 0;
} else {
pwm_toggle = 1;
// request pwm_tim1_intr_handler to swap the timing buffers
pwm_toggle_request = 1;
}
UNLOCK_PWM(critical); // leave critical
@ -297,12 +301,18 @@ pwm_get_freq(uint8 channel) {
STATIC void ICACHE_RAM_ATTR
pwm_tim1_intr_handler(void *dummy) {
(void)dummy;
uint8 local_toggle = pwm_toggle; // pwm_toggle may change outside
RTC_CLR_REG_MASK(FRC1_INT_ADDRESS, FRC1_INT_CLR_MASK);
if (pwm_current_channel >= (*pwm_channel - 1)) { // *pwm_channel may change outside
pwm_single = pwm_single_toggle[local_toggle];
pwm_channel = &pwm_channel_toggle[local_toggle];
if (pwm_toggle_request != 0) {
pwm_toggle ^= 1;
pwm_toggle_request = 0;
}
pwm_single = pwm_single_toggle[pwm_toggle];
pwm_channel = &pwm_channel_toggle[pwm_toggle];
gpio_output_set(pwm_single[*pwm_channel - 1].gpio_set,
pwm_single[*pwm_channel - 1].gpio_clear,