Pulse With Modulation

[espressif]

Pulse With Modulation

hi,
If you want to use RTOS task and timer to implement pwm, it will be very low resolution.
Please refer to pwm.c in IOT_example, which uses FRC1 interrupt to implement pwm, can get us resolution.
OS version SDK uses _xt_isr_unmask, _xt_isr_mask and _xt_isr_attach to handle isr.
We will release FRC1, pwm example later.

[Karang]

Thank you for your answer.
I'm using pwm.c from iot_example, and it worked with _xt_isr_unmask, _xt_isr_mask and _xt_isr_attach. It compiles and doesn't crash anymore but still no pwm ;(
https://github.com/Karang/Ardunet/blob/master/src/ardunetcore/pwm.c
I will continue my experimentations, but an example would be really great.

[qdk0901]

Below code works fine for me

#include "esp_common.h"
#include "esp8266/timer_register.h"
#include "esp8266/ets_sys.h"
#include "driver/pwm.h"

#define US_TO_RTC_TIMER_TICKS(t)
((t) ?
(((t) > 0x35A) ?
(((t)>>2) * ((APB_CLK_FREQ>>4)/250000) + ((t)&0x3) * ((APB_CLK_FREQ>>4)/1000000)) :
(((t) *(APB_CLK_FREQ>>4)) / 1000000)) :
0)

#define FRC1_ENABLE_TIMER 0x80

static struct pwm_single_param pwm_single_toggle[2][PWM_CHANNEL + 1];
static struct pwm_single_param *pwm_single;

static struct pwm_param pwm;

static uint8 pwm_out_io_num[PWM_CHANNEL] = {PWM_1_OUT_IO_NUM, PWM_0_OUT_IO_NUM, PWM_2_OUT_IO_NUM};

static uint8 pwm_channel_toggle[2];
static uint8 *pwm_channel;

static uint8 pwm_toggle = 1;
static uint8 pwm_timer_down = 1;

static uint8 pwm_current_channel = 0;

static uint16 pwm_gpio = 0;

typedef enum {
DIVDED_BY_1 = 0,
DIVDED_BY_16 = 4,
DIVDED_BY_256 = 8,
} TIMER_PREDIVED_MODE;

typedef enum {
TM_LEVEL_INT = 1,
TM_EDGE_INT = 0,
} TIMER_INT_MODE;

void ICACHE_FLASH_ATTR pwm_insert_sort(struct pwm_single_param pwm[], uint8 n)
{
uint8 i;

for (i = 1; i < n; i++) {
    if (pwm[i].h_time < pwm[i - 1].h_time) {
        int8 j = i - 1;
        struct pwm_single_param tmp;

        memcpy(&tmp, &pwm[i], sizeof(struct pwm_single_param));
        memcpy(&pwm[i], &pwm[i - 1], sizeof(struct pwm_single_param));

        while (tmp.h_time < pwm[j].h_time) {
            memcpy(&pwm[j + 1], &pwm[j], sizeof(struct pwm_single_param));
            j--;
            if (j < 0) {
                break;
            }
        }

        memcpy(&pwm[j + 1], &tmp, sizeof(struct pwm_single_param));
    }
}

}

void ICACHE_FLASH_ATTR pwm_start(void)
{
uint8 i, j;

struct pwm_single_param *local_single = pwm_single_toggle[pwm_toggle ^ 0x01];
uint8 *local_channel = &pwm_channel_toggle[pwm_toggle ^ 0x01];

// step 1: init PWM_CHANNEL+1 channels param
for (i = 0; i < PWM_CHANNEL; i++) {
    uint32 us = pwm.period * pwm.duty[i] / PWM_DEPTH;
    local_single[i].h_time = US_TO_RTC_TIMER_TICKS(us);
    local_single[i].gpio_set = 0;
    local_single[i].gpio_clear = 1 << pwm_out_io_num[i];
}

local_single[PWM_CHANNEL].h_time = US_TO_RTC_TIMER_TICKS(pwm.period);
local_single[PWM_CHANNEL].gpio_set = pwm_gpio;
local_single[PWM_CHANNEL].gpio_clear = 0;

// step 2: sort, small to big
pwm_insert_sort(local_single, PWM_CHANNEL + 1);

*local_channel = PWM_CHANNEL + 1;

// step 3: combine same duty channels
for (i = PWM_CHANNEL; i > 0; i--) {
    if (local_single[i].h_time == local_single[i - 1].h_time) {
        local_single[i - 1].gpio_set |= local_single[i].gpio_set;
        local_single[i - 1].gpio_clear |= local_single[i].gpio_clear;

        for (j = i + 1; j < *local_channel; j++) {
            memcpy(&local_single[j - 1], &local_single[j], sizeof(struct pwm_single_param));
        }

        (*local_channel)--;
    }
}

// step 4: cacl delt time
for (i = *local_channel - 1; i > 0; i--) {
    local_single[i].h_time -= local_single[i - 1].h_time;
}

// step 5: last channel needs to clean
local_single[*local_channel-1].gpio_clear = 0;

// step 6: if first channel duty is 0, remove it
if (local_single[0].h_time == 0) {
    local_single[*local_channel - 1].gpio_set &= ~local_single[0].gpio_clear;
    local_single[*local_channel - 1].gpio_clear |= local_single[0].gpio_clear;

    for (i = 1; i < *local_channel; i++) {
        memcpy(&local_single[i - 1], &local_single[i], sizeof(struct pwm_single_param));
    }

    (*local_channel)--;
}

// if timer is down, need to set gpio and start timer
if (pwm_timer_down == 1) {
    pwm_channel = local_channel;
    pwm_single = local_single;
    // start
    gpio_output_set(local_single[0].gpio_set, local_single[0].gpio_clear, pwm_gpio, 0);

    // yeah, if all channels' duty is 0 or 255, don't need to start timer, otherwise start...
    if (*local_channel != 1) {
        pwm_timer_down = 0;
        WRITE_PERI_REG(FRC1_LOAD_ADDRESS, local_single[0].h_time);
    }
}

if (pwm_toggle == 1) {
    pwm_toggle = 0;
} else {
    pwm_toggle = 1;
}

}

/******************************************************************************

• FunctionName : pwm_set_duty
• Description : set each channel's duty params
• Parameters : uint8 duty : 0 ~ PWM_DEPTH

•            uint8 channel : channel index
  

• Returns : NONE
  *******************************************************************************/
  void ICACHE_FLASH_ATTR pwm_set_duty(uint8 duty, uint8 channel)
  {
  if (duty < 1) {
  pwm.duty[channel] = 0;
  } else if (duty >= PWM_DEPTH) {
  pwm.duty[channel] = PWM_DEPTH;
  } else {
  pwm.duty[channel] = duty;
  }
  }

/******************************************************************************

• FunctionName : pwm_set_freq

• Description : set pwm frequency

• Parameters : uint16 freq : 100hz typically

• Returns : NONE
  *******************************************************************************/
  void ICACHE_FLASH_ATTR pwm_set_freq(uint16 freq)
  {
  if (freq > 500) {
  pwm.freq = 500;
  } else if (freq < 1) {
  pwm.freq = 1;
  } else {
  pwm.freq = freq;
  }

  pwm.period = PWM_1S / pwm.freq;
  }

/******************************************************************************

• FunctionName : pwm_set_freq_duty

• Description : set pwm frequency and each channel's duty

• Parameters : uint16 freq : 100hz typically

•            uint8 *duty : each channel's duty
  

• Returns : NONE
  *******************************************************************************/
  void ICACHE_FLASH_ATTR pwm_set_freq_duty(uint16 freq, uint8 *duty)
  {
  uint8 i;

  pwm_set_freq(freq);

  for (i = 0; i < PWM_CHANNEL; i++) {
  pwm_set_duty(duty[i], i);
  }
  }

/******************************************************************************

• FunctionName : pwm_get_duty
• Description : get duty of each channel
• Parameters : uint8 channel : channel index
• Returns : NONE
  *******************************************************************************/
  uint8 ICACHE_FLASH_ATTR pwm_get_duty(uint8 channel)
  {
  return pwm.duty[channel];
  }

/******************************************************************************

• FunctionName : pwm_get_freq
• Description : get pwm frequency
• Parameters : NONE
• Returns : uint16 : pwm frequency
  *******************************************************************************/
  uint16 ICACHE_FLASH_ATTR pwm_get_freq(void)
  {
  return pwm.freq;
  }

/******************************************************************************

• FunctionName : pwm_period_timer

• Description : pwm period timer function, output high level,

•            start each channel's high level timer
  

• Parameters : NONE

• Returns : NONE
  *******************************************************************************/
  void LOCAL pwm_tim1_intr_handler(void)
  {
  CLEAR_PERI_REG_MASK(FRC1_INT_ADDRESS, FRC1_INT_CLR_MASK);

  if (pwm_current_channel == (*pwm_channel - 1)) {
  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,
                  pwm_gpio,
                  0);
  
  pwm_current_channel = 0;
  
  if (*pwm_channel != 1) {
      WRITE_PERI_REG(FRC1_LOAD_ADDRESS, pwm_single[pwm_current_channel].h_time);
  } else {
      pwm_timer_down = 1;
  }
  

  } else {
  gpio_output_set(pwm_single[pwm_current_channel].gpio_set,
  pwm_single[pwm_current_channel].gpio_clear,
  pwm_gpio, 0);

  pwm_current_channel++;
  WRITE_PERI_REG(FRC1_LOAD_ADDRESS, pwm_single[pwm_current_channel].h_time);
  

  }
  }

void ICACHE_FLASH_ATTR pwm_init(uint16 freq, uint8 *duty)
{
int i;

_xt_isr_attach(ETS_FRC_TIMER1_INUM, pwm_tim1_intr_handler);
TM1_EDGE_INT_ENABLE();

//enable timer1 interrupt
_xt_isr_unmask((1 << ETS_FRC_TIMER1_INUM));

CLEAR_PERI_REG_MASK(FRC1_INT_ADDRESS, FRC1_INT_CLR_MASK);
WRITE_PERI_REG(FRC1_CTRL_ADDRESS,  //FRC2_AUTO_RELOAD|
              DIVDED_BY_16
              | FRC1_ENABLE_TIMER
              | TM_EDGE_INT);

WRITE_PERI_REG(FRC1_LOAD_ADDRESS, 0); 

PIN_FUNC_SELECT(PWM_0_OUT_IO_MUX, PWM_0_OUT_IO_FUNC);
PIN_FUNC_SELECT(PWM_1_OUT_IO_MUX, PWM_1_OUT_IO_FUNC);
PIN_FUNC_SELECT(PWM_2_OUT_IO_MUX, PWM_2_OUT_IO_FUNC);

for (i = 0; i < PWM_CHANNEL; i++) {
    pwm_gpio |= (1 << pwm_out_io_num[i]);
}

pwm_set_freq_duty(freq, duty);

pwm_start();

}