Implementing time delay without delay(), millis() and delayMicroseconds()

Hi everyone!
I want to implement a timing delay of 1us in my program. But for some reason Timer0 is being disabled, and can't use the delay(), millis() and delayMicroseconds().
So is there a way I can implement a delay of 1us without using these functions?

Thanks in advance :slightly_smiling_face:

Could it be happening in the code that you have not posted ?

Please follow the advice given in the link below when posting code, in particular the section entitled 'Posting code and common code problems'

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Hi, @gourie
Welcome to the forum.

Can you tell us what your project is, what do you want it to do and why you need 1us delay?

Thanks.. Tom.. :grinning: :+1: :coffee: :australia:

are you sure that you want a 1 microsecond delay?
1 microsecond = 0,000001 seconds
Without knowing anything about your project I suggest
take another microcontroller code a ISR that has the desired delay

best regards Stefan

In the task void fDoParticleDetector( void * parameter ), I have a 280us delay, not using delay(), millis() and delayMicroseconds(). The timer delay is non-blocking. Changing esp_timer_start_once( oneshot_timer, 280 ); time from 280 to esp_timer_start_once( oneshot_timer, 1 ); would give a 1us delay.

#include <WiFi.h>
#include <PubSubClient.h>
#include "certs.h" // include the connection infor for WiFi and MQTT
#include "sdkconfig.h" // used for log printing
#include "esp_system.h"
#include "freertos/FreeRTOS.h" //freeRTOS items to be used
#include "freertos/task.h"
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include "Adafruit_BME680.h"
#include <Adafruit_GFX.h>    // Core graphics library
#include <Adafruit_ST7789.h> // Hardware-specific library for ST7789
#include <driver/adc.h>
#include "esp32-hal-ledc.h"
#include <HardwareSerial.h>
#include <SimpleKalmanFilter.h>
#include "MHZ19.h"
#include <ESP32Time.h>
#include <SolarCalculator.h>
////
ESP32Time rtc;
MHZ19 myMHZ19;
////
Adafruit_BME680 bme( GPIO_NUM_5 ); // use hardware SPI, set GPIO pin to use
//Adafruit_ST7789 tft = Adafruit_ST7789( TFT_CS     , TFT_DC    , TFT_MOSI   , TFT_SCLK   , TFT_RST     );
Adafruit_ST7789 tft   = Adafruit_ST7789( GPIO_NUM_15, GPIO_NUM_0, GPIO_NUM_13, GPIO_NUM_14, GPIO_NUM_22 );
WiFiClient   wifiClient; // do the WiFi instantiation thing
PubSubClient MQTTclient( mqtt_server, mqtt_port, wifiClient ); //do the MQTT instantiation thing
//////
#define evtDoParticleRead     ( 1 << 0 ) // declare an event
#define evtWaitForBME         ( 1 << 1 )
#define evtParseMQTT          ( 1 << 3 )
EventGroupHandle_t eg; // variable for the event group handle
//////
QueueHandle_t xQ_WindChillDewPoint;
QueueHandle_t xQ_eData; // environmental data to be displayed on the screen
struct stu_eData
{
  float  Temperature = 0.0f;
  float  Pressure    = 0.0f;
  float  Humidity    = 0.0f;
  float  IAQ         = 0.0f; // Index Air Quality
  float  RM0         = 0.0f; // Remaining Moisture from sensor 0
  float  PM2         = 0.0f; // particles in air
  float  WS          = 0.0f; // wind speed
  String WD          = "";   // wind direction
  float  RF          = 0.0f; // rainfall
  float  WSV         = 0.0f; // weather station volts
  float  WSC         = 0.0f; // weather station current
  float  WSP         = 0.0f; // weather station power
  float  WindChill   = 0.0f; //windchill
  float  DewPoint    = 0.0f; //dew point or dew index
  int    SunRiseHr   = 0;    // sunrise hour
  int    SunRiseMin  = 0;    //sunrise minute
  int    SunSetHr    = 0;    //sunset hour
  int    SunSetMin   = 0;    //sunset minute
  int    DuskHr      = 0;    //dusk
  int    DuskMin     = 0;    //dusk
  int    DawnHr      = 0;    // dawn
  int    DawnMin     = 0;    // dawn
  int    TransitHr   = 0;    // 'noon' time
  int    TransitMin  = 0;    // 'noon' time
  double azimuth     = 0.0f;   // Sun's azimuth, in degrees
  double elevation   = 0.0f;     // Sun's elevation, in degrees
} x_eData; // environmental data
QueueHandle_t xQ_Message; // payload and topic queue of MQTT payload and topic
const int payloadSize = 100;
struct stu_message
{
  char payload [payloadSize] = {'\0'};
  String topic ;
} x_message;
////
const float oGasResistanceBaseLine = 149598.0f;
int mqttOK = 0;
int CO2    = 0;
volatile bool TimeSet = false;
//////
esp_timer_handle_t oneshot_timer; //veriable to store the hardware timer handle
//////
SemaphoreHandle_t sema_MQTT_KeepAlive;
SemaphoreHandle_t sema_PublishPM;
SemaphoreHandle_t sema_mqttOK;
////
//serial(2) = pin25 RX, pin26 TX
HardwareSerial co2Serial ( 2 );
//////
// interrupt service routine for WiFi events put into IRAM
void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
{
  switch (event) {
    case SYSTEM_EVENT_STA_CONNECTED:
      log_i("Connected to WiFi access point");
      break;
    case SYSTEM_EVENT_STA_DISCONNECTED:
      log_i("Disconnected from WiFi access point");
      break;
    case SYSTEM_EVENT_AP_STADISCONNECTED:
      log_i("WiFi client disconnected");
      break;
    default: break;
  }
} // void IRAM_ATTR WiFiEvent(WiFiEvent_t event)
//////
void IRAM_ATTR oneshot_timer_callback( void* arg )
{
  BaseType_t xHigherPriorityTaskWoken;
  xEventGroupSetBitsFromISR( eg, evtDoParticleRead, &xHigherPriorityTaskWoken );
} //void IRAM_ATTR oneshot_timer_callback( void* arg )
//////
void IRAM_ATTR mqttCallback(char* topic, byte * payload, unsigned int length)
{
  memset( x_message.payload, '\0', payloadSize ); // clear payload char buffer
  x_message.topic = ""; //clear topic string buffer
  x_message.topic = topic; //store new topic
  int i = 0; // extract payload
  for ( i; i < length; i++)
  {
    x_message.payload[i] = ((char)payload[i]);
  }
  x_message.payload[i] = '\0';
  xQueueOverwrite( xQ_Message, (void *) &x_message );// send data to queue
} // void mqttCallback(char* topic, byte* payload, unsigned int length)
////
void setup()
{
  co2Serial.begin( 9600 , SERIAL_8N1, 25, 26 ); // pin25 RX, pin26 TX
  x_eData.WD.reserve(50);
  x_message.topic.reserve( payloadSize );
  xQ_WindChillDewPoint = xQueueCreate( 1, sizeof(stu_eData) );
  xQ_Message  = xQueueCreate( 1, sizeof(stu_message) );
  xQ_eData    = xQueueCreate( 1, sizeof(stu_eData) ); // sends a queue copy of the structure
  //
  sema_PublishPM = xSemaphoreCreateBinary();
  xSemaphoreGive( sema_PublishPM );
  sema_mqttOK    =  xSemaphoreCreateBinary();
  xSemaphoreGive( sema_mqttOK );
  //
  ledcSetup( 4, 12000, 8 ); // ledc: 4  => Group: 0, Channel: 2, Timer: 1, led frequency, resolution  bits
  ledcAttachPin( GPIO_NUM_12, 4 );   // gpio number and channel
  ledcWrite( 4, 0 ); // write to channel number 4
  //
  eg = xEventGroupCreate(); // get an event group handle
  // output mode
  gpio_config_t io_cfg = {}; // initialize the gpio configuration structure
  io_cfg.mode = GPIO_MODE_OUTPUT; // set gpio mode
  io_cfg.pin_bit_mask = ( (1ULL << GPIO_NUM_4) ); //bit mask of the pins to set
  gpio_config(&io_cfg); // configure the gpio based upon the parameters as set in the configuration structure
  gpio_set_level( GPIO_NUM_4, LOW); // set air particle sensor trigger pin to LOW
  // input mode
  io_cfg = {}; // reinitialize the gpio configuration structure
  io_cfg.mode = GPIO_MODE_INPUT; // set gpio mode. GPIO_NUM_0 input from water level sensor
  io_cfg.pin_bit_mask = ( (1ULL << GPIO_NUM_0) | (1ULL << GPIO_NUM_27)  ); //bit mask of the pins to set, assign gpio number to be configured
  gpio_config(&io_cfg); // configure the gpio based upon the parameters as set in the configuration structure
  // set up A:D channels, refer: https://dl.espressif.com/doc/esp-idf/latest/api-reference/peripherals/adc.html
  adc1_config_width(ADC_WIDTH_12Bit);
  adc1_config_channel_atten(ADC1_CHANNEL_0, ADC_ATTEN_DB_11);// using GPIO 36
  // https://docs.espressif.com/projects/esp-idf/en/latest/esp32/api-reference/system/esp_timer.html?highlight=hardware%20timer High Resoultion Timer API
  esp_timer_create_args_t oneshot_timer_args = {}; // initialize High Resoulition Timer (HRT) configuration structure
  oneshot_timer_args.callback = &oneshot_timer_callback; // configure for callback, name of callback function
  esp_timer_create( &oneshot_timer_args, &oneshot_timer ); // assign configuration to the HRT, receive timer handle
  //
  xTaskCreatePinnedToCore( fparseMQTT, "fparseMQTT", 7000,  NULL, 5, NULL, 1 );
  xTaskCreatePinnedToCore( MQTTkeepalive, "MQTTkeepalive", 5000, NULL, 6, NULL, 1 );
  xTaskCreatePinnedToCore( DoTheBME680Thing, "DoTheBME280Thing", 20000, NULL, 5, NULL, 1);
  xTaskCreatePinnedToCore( fDoParticleDetector, "fDoParticleDetector", 6000, NULL, 3, NULL, 1 );
  xTaskCreatePinnedToCore( fmqttWatchDog, "fmqttWatchDog", 5000, NULL, 3, NULL, 1 );
  xTaskCreatePinnedToCore( fDoTheDisplayThing, "fDoTheDisplayThing", 23000, NULL, 3, NULL, 1 );
  xTaskCreatePinnedToCore( fScreenBlanking, "fScreenBlanking", 2000, NULL, 2, NULL, 1 );
  xTaskCreatePinnedToCore( fGetCO2, "fGetCO2", 4500, NULL, 2, NULL, 1 );
  xTaskCreatePinnedToCore( fParseDewPointWindChill, "fParseDewPointWindChill", 4500, NULL, 2, NULL, 1 );
  xTaskCreatePinnedToCore( fSolarCalculations, "fSolarCalculations", 10000, NULL, 2, NULL, 1 );
} //void setup()
////
void fSolarCalculations ( void *pvParameters )
{
  double latitude  = 43.618881;
  double longitude = -116.215019;
  double sunrise;  // Sunrise, in hours (UTC)
  double transit;  // Solar noon, in hours (UTC)
  double sunset;   // Sunset, in hours (UTC)
  double dawn;     // Civil dawn, in hours (UTC)
  double dusk;     // Civil dusk, in hours (UTC)
  //double rt_ascension;  // Sun's right ascension, in degrees
  //double declination;   // Sun's declination, in degrees
  const  float time_zone = -7.0f;
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 1000; //delay for mS
  int count  = 3590;
  int monthX = 1;
  int dayX   = 1;
  for (;;)
  {
    if ( count % 60 == 0 )
    {
      if ( (rtc.getHour(true) >= 12) & (rtc.getHour(true) <= 23) )
      {
        dayX = 0;
      } else {
        dayX = 1;
      }
      calcSunriseSunset( rtc.getYear(), (rtc.getMonth() + monthX) , (rtc.getDay() + dayX), latitude, longitude, transit, sunrise, sunset );  // Calculate the times of sunrise, transit and sunset
      sunrise += time_zone;
      sunset  += time_zone;
      SolarTimeFormat( sunrise, 0 );
      SolarTimeFormat( sunset, 1 );      
      calcCivilDawnDusk( rtc.getYear(), (rtc.getMonth() + monthX) , rtc.getDay(), latitude, longitude, transit, dawn, dusk); // Calculate the times of civil dawn and dusk (UTC)
      transit += time_zone;
      dawn    += time_zone;
      dusk    += time_zone;
      SolarTimeFormat( dawn, 2 );
      SolarTimeFormat( dusk, 3 );
      SolarTimeFormat( transit, 4 );      
      calcHorizontalCoordinates( rtc.getYear(), (rtc.getMonth() + monthX) , rtc.getDay(),  rtc.getHour() , rtc.getMinute(), rtc.getSecond(), latitude, longitude, x_eData.azimuth, x_eData.elevation );
      x_eData.azimuth   = double(round(x_eData.azimuth * 100)) / 100; // Round to two decimal places
      x_eData.elevation = double(round(x_eData.elevation * 100)) / 100;
      if (count >= 3600 )
      {
        SolarTimeFormat( 0.0f, 5 ); // publish MQTT
        log_i( "Azimuth %f, elevation %f, transit %dhr %dmin, dawn %dhr %dmin, dusk %dhr %dmin", x_eData.azimuth, x_eData.elevation, x_eData.TransitHr, x_eData.TransitMin, x_eData.DawnHr, x_eData.DawnMin, x_eData.DuskHr, x_eData.DuskMin );
        count = 0;
      }
    }
    //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
    count++;
  } //for (;;)
  vTaskDelete( NULL );
} //void fSolarCalculations ( )
////
void SolarTimeFormat( double h, int i  )
{
  int hours   = 0;
  int minutes = 0;
  if ( h != 0.0f )
  {
    int m = int(round(h * 60));
    hours = (m / 60) % 24;
    minutes = m % 60;
  }
  switch ( i )
  {
    case 0:
      x_eData.SunRiseHr = hours;
      x_eData.SunRiseMin = minutes;
      break;
    case 1:
      x_eData.SunSetHr = hours;
      x_eData.SunSetMin = minutes;
      break;
    case 2:
      x_eData.DawnHr = hours;
      x_eData.DawnMin = minutes;
      break;
    case 3:
      x_eData.DuskHr = hours;
      x_eData.DawnMin = minutes;
      break;
    case 4:
      x_eData.TransitHr = hours;
      x_eData.TransitMin = minutes;
      break;
    case 5:
      String sTopic = "";
      sTopic.reserve( 35 );
      sTopic.concat( String(x_eData.SunRiseHr) + "," );
      sTopic.concat( String(x_eData.SunRiseMin) + "," );
      sTopic.concat( String(x_eData.SunSetHr) + "," );
      sTopic.concat( String(x_eData.SunSetMin) + "," );
      sTopic.concat( String(x_eData.DawnHr) + "," );
      sTopic.concat( String(x_eData.DawnMin) + "," );
      sTopic.concat( String(x_eData.TransitHr) + "," );
      sTopic.concat( String(x_eData.TransitMin) );
      sTopic = "";
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
      MQTTclient.publish( topicSRSSDDT, sTopic.c_str() );
      xSemaphoreGive( sema_MQTT_KeepAlive );
      sTopic.concat( String(x_eData.azimuth) + "," + String(x_eData.azimuth) );
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
      MQTTclient.publish( topicAzEle, sTopic.c_str() );
      xSemaphoreGive( sema_MQTT_KeepAlive );
      sTopic = "";
      break;
  } // switch ( i ) {
} // void SolarTimeFormat( double h, int i  )
/*
  250-400ppm Normal background concentration in outdoor ambient air
  400-1,000ppm  Concentrations typical of occupied indoor spaces with good air exchange
  1,000-2,000ppm  Complaints of drowsiness and poor air.
  2,000-5,000 ppm Headaches, sleepiness and stagnant, stale, stuffy air. Poor concentration, loss of attention, increased heart rate and slight nausea may also be present.
  5,000 Workplace exposure limit (as 8-hour TWA) in most jurisdictions.
  >40,000 ppm Exposure may lead to serious oxygen deprivation resulting in permanent brain damage, coma, even death.
*/
void fParseDewPointWindChill( void *pvParameters )
{
  while ( !MQTTclient.connected() )
  {
    vTaskDelay( 250 );
  }
  struct stu_message px_message;
  String sDewPoint = "";
  String sWindChill = "";
  sDewPoint.reserve( payloadSize );
  sWindChill.reserve( payloadSize );
  for (;;)
  {
    if ( xQueueReceive(xQ_WindChillDewPoint, &px_message, portMAX_DELAY) == pdTRUE )
    {
      sDewPoint = px_message.payload;
      int commaIndex = sDewPoint.indexOf(',');
      sWindChill.concat ( sDewPoint.substring(0, commaIndex) );
      sDewPoint.remove( 0, (commaIndex + 1) );
      x_eData.WindChill = sWindChill.toFloat();
      x_eData.DewPoint = sDewPoint.toFloat();
      sDewPoint = "";
      sWindChill = "";
    }
    //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
  }
  vTaskDelete( NULL );
}
////
void fGetCO2 ( void *pvParameters )
{
  uint64_t TimePastKalman  = esp_timer_get_time();
  myMHZ19.begin( co2Serial );
  myMHZ19.autoCalibration();
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 1000; //delay for mS
  SimpleKalmanFilter KF_CO2( 1.0f, 1.0f, .01f );
  for ( ;; )
  {
    KF_CO2.setProcessNoise( (esp_timer_get_time() - TimePastKalman) / 1000000.0f );
    CO2 = KF_CO2.updateEstimate( myMHZ19.getCO2() ); // apply simple Kalman filter
    TimePastKalman = esp_timer_get_time();
    xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
    MQTTclient.publish( topicCO2, String(CO2).c_str() );
    xSemaphoreGive( sema_MQTT_KeepAlive );
    // process wind chill and dew point
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
    //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
  }
  vTaskDelete( NULL );
} //void fMHZ19B ( void *pvParameters )
////
void fScreenBlanking( void *pvParameters )
{
  int       TimeOfPause = 10000 * 1000;
  uint64_t  PauseStartTime = esp_timer_get_time();
  bool      Pause = false;
  const int brightness = 250;
  int       countUpDown = brightness;
  for ( ;; )
  {
    if (!Pause )
    {
      //if motion detect then show display otherwise blank display
      if ( !(gpio_get_level( GPIO_NUM_27)) )
      {
        for ( countUpDown; countUpDown-- > 0; )
        {
          ledcWrite( 4, countUpDown ); // write to channel number 4, dim backlight
          vTaskDelay( 7 );
        }
      } else {
        Pause = true;
        PauseStartTime = esp_timer_get_time();
        ledcWrite( 4, brightness );
        countUpDown = brightness;
      }
    } else {
      // still detecting movement reset blanking pause time
      if ( gpio_get_level( GPIO_NUM_27) )
      {
        PauseStartTime = esp_timer_get_time(); // extend pause blanking time
      }
      if ( (esp_timer_get_time() - PauseStartTime) >= TimeOfPause )
      {
        Pause = false;
      }
    }
    vTaskDelay( 250 );
  }
  vTaskDelete( NULL );
} //void fScreenBlanking( void *pvParameters )
//////
void fparseMQTT( void *pvParameters )
{
  struct stu_message px_message;
  for (;;)
  {
    if ( xQueueReceive(xQ_Message, &px_message, portMAX_DELAY) == pdTRUE )
    {
      xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
      mqttOK = 0;
      xSemaphoreGive( sema_mqttOK );
      if ( px_message.topic == topicRemainingMoisture_0 )
      {
        x_eData.RM0  = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicWindSpeed )
      {
        x_eData.WS = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicWindDirection )
      {
        x_eData.WD = "";
        x_eData.WD = String(px_message.payload);
      }
      if ( px_message.topic == topicRainfall )
      {
        x_eData.RF = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicWSVolts )
      {
        x_eData.WSV = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicWSCurrent )
      {
        x_eData.WSC = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicWSPower )
      {
        x_eData.WSP = String(px_message.payload).toFloat();
      }
      if ( px_message.topic == topicDPnWI )
      {
        xQueueSend( xQ_WindChillDewPoint, (void *) &px_message, 1 );
      }
      if ( String(px_message.topic) == topicOK )
      {
        if ( !TimeSet)
        {
          String temp = "";
          temp.reserve(50);
          temp.concat( String(px_message.payload[0]) );
          temp.concat( String(px_message.payload[1]) );
          temp.concat( String(px_message.payload[2]) );
          temp.concat( String(px_message.payload[3]) );
          int year =  temp.toInt();
          temp = "";
          temp.concat( String(px_message.payload[5]) + String(px_message.payload[6]) );
          int month =  temp.toInt();
          temp =  "";
          temp.concat(String(px_message.payload[8]) + String(px_message.payload[9]) );
          int day =  temp.toInt();
          temp = "";
          temp.concat( String(px_message.payload[11]) + String(px_message.payload[12]) );
          int hour =  temp.toInt();
          temp = "";
          temp.concat( String(px_message.payload[14]) + String(px_message.payload[15]) );
          int min =  temp.toInt();
          rtc.setTime( 0, min, hour, day, month, year );
          log_i( "rtc  %s Year %d month %d day %d", rtc.getTime(), rtc.getYear(), (rtc.getMonth() + 1), rtc.getDay() );
          TimeSet = true;
        }
      }
    } //if ( xQueueReceive(xQ_Message, &px_message, portMAX_DELAY) == pdTRUE )
  } //for(;;)
  vTaskDelete( NULL );
} // void fparseMQTT( void *pvParameters )
////
void fDoTheDisplayThing( void * parameter )
{
  tft.init( 240, 320 ); // Init ST7789 320x240
  tft.setRotation( 3 );
  tft.setTextSize( 3 );
  tft.fillScreen( ST77XX_BLACK );
  tft.setTextWrap( false );
  struct stu_eData px_eData;
  const int brightness = 250;
  ledcWrite( 4, brightness ); //backlight set
  const int MaxString      = 20;
  String oldTempString     = "";
  String oldHumidityString = "";
  String oldAQIString      = "";
  String oldRainfall       = "";
  String oldWindDirection  = "";
  String oldAirPressure    = "";
  String oldRMO            = "";
  String oldPM2            = "";
  String oldPower          = "";
  oldHumidityString.reserve( MaxString );
  oldWindDirection.reserve( MaxString );
  oldAirPressure.reserve( MaxString );
  oldTempString.reserve( MaxString );
  oldAQIString.reserve( MaxString );
  oldRainfall.reserve( MaxString );
  oldPower.reserve( MaxString );
  oldRMO.reserve( MaxString );
  oldPM2.reserve( MaxString );
  bool Tick = true;
  const int numOfColors = 40;
  /* https://chrishewett.com/blog/true-rgb565-colour-picker/#:~:text=A%20true%20RGB565%20colour%20picker%2021st%20Oct%202017,in%205%20bits%20and%20green%20in%206%20bits. */
  int colors[numOfColors] = { ST77XX_BLACK, ST77XX_RED, ST77XX_WHITE, ST77XX_BLUE, ST77XX_GREEN, ST77XX_CYAN, ST77XX_MAGENTA, ST77XX_YELLOW, 0xd55b, 0xee09,
                              0x2e15, 0xcb43, 0x6bad, 0x126f, 0x1264, 0xe264, 0xe7e4, 0x87e4, 0x87fe, 0x876a,
                              0xe304, 0x1cc4, 0xf4c4, 0xf4da, 0xcf66, 0xa879, 0x7f28, 0x4f37, 0xfa97, 0x6195,
                              0X8162, 0xc962, 0x517b, 0x325b, 0xea5b, 0x179b, 0xff80, 0xf960, 0x416d, 0x7bd1
                            };
  int colorCounter = 1;
  for (;;)
  {
    if ( xQueueReceive(xQ_eData, &px_eData, portMAX_DELAY) == pdTRUE )
    {
      tft.setCursor( 0, 0 );
      tft.setTextColor( colors[0] );
      tft.print( oldTempString );
      tft.setCursor( 0, 0 );
      tft.setTextColor( colors[colorCounter] );
      oldTempString = "";
      if ( Tick )
      {
        oldTempString.concat( "iTemp " + String(px_eData.Temperature) + "F" );
      } else {
        oldTempString.concat( "Wind Chill " + String(px_eData.WindChill) + "F" );
      }
      tft.println( oldTempString );
      tft.setCursor( 0, 30 );
      tft.setTextColor( colors[0] );
      tft.print( oldHumidityString );
      tft.setCursor( 0, 30 );
      tft.setTextColor( colors[colorCounter] );
      oldHumidityString = "";
      if ( Tick )
      {
        oldHumidityString.concat( "iHum  " + String(px_eData.Humidity) + "%" );
      } else {
        if ( (px_eData.SunRiseHr < 10) & (px_eData.SunRiseMin < 10) )
        {
          oldHumidityString.concat( "sRise 0" + String(px_eData.SunRiseHr) + "0" + String(px_eData.SunRiseMin) );
        }
        if ( (px_eData.SunRiseHr >= 10) & (px_eData.SunRiseMin < 10) )
        {
          oldHumidityString.concat( "sRise " + String(px_eData.SunRiseHr) + "0" + String(px_eData.SunRiseMin) );
        }
        if ( (px_eData.SunRiseHr < 10) & (px_eData.SunRiseMin >= 10) )
        {
          oldHumidityString.concat( "sRise 0" + String(px_eData.SunRiseHr) + String(px_eData.SunRiseMin) );
        }
        if ( (px_eData.SunRiseHr >= 10) & (px_eData.SunRiseMin >= 10) )
        {
          oldHumidityString.concat( "sRise " + String(px_eData.SunRiseHr) + String(px_eData.SunRiseMin) );
        }
      }
      tft.println( oldHumidityString );
      tft.setCursor( 0, 60 );
      tft.setTextColor( colors[0] );
      tft.print( oldAirPressure );
      tft.setCursor( 0, 60 );
      tft.setTextColor( colors[colorCounter] );
      oldAirPressure = "";
      if ( Tick )
      {
        //oldAirPressure.concat( "Pres " + String(px_eData.Pressure) + "mmHg" );
        oldAirPressure.concat( "Dew Pt. " + String(px_eData.DewPoint) + "F" );
      } else {
        if ( px_eData.SunSetMin < 10 )
        {
          oldAirPressure.concat( "sSet " + String(px_eData.SunSetHr) + "0" + String(px_eData.SunSetMin) );
        }
        if ( px_eData.SunRiseMin >= 10 )
        {
          oldAirPressure.concat( "sSet " + String(px_eData.SunSetHr) + String(px_eData.SunSetMin) );
        }
      }
      tft.println( oldAirPressure );
      tft.setCursor( 0, 90 );
      tft.setTextColor( colors[0] );
      tft.print( oldAQIString );
      tft.setCursor( 0, 90 );
      tft.setTextColor( colors[colorCounter] );
      oldAQIString = "";
      oldAQIString.concat( "iAQI " + String(px_eData.IAQ) + "%" );
      tft.println( oldAQIString );
      tft.setCursor( 0, 120 );
      tft.setTextColor( colors[0] );
      tft.print( oldRMO );
      tft.setCursor( 0, 120 );
      tft.setTextColor( colors[colorCounter] );
      oldRMO = "";
      if ( Tick )
      {
        oldRMO.concat( "iRM0 " + String(px_eData.RM0) + "%" );
      } else {
        oldRMO.concat( "iCO2 " + String(CO2) + "ppm" );
      }
      tft.println( oldRMO );
      tft.setCursor( 0, 150 );
      tft.setTextColor( colors[0] );
      tft.print( oldPM2 );
      tft.setCursor( 0, 150 );
      tft.setTextColor( colors[colorCounter] );
      oldPM2 = "";
      oldPM2.concat( "PM2 " + String(px_eData.PM2) + "ug/m3" );
      tft.println( oldPM2 );
      tft.setCursor( 0, 180 );
      tft.setTextColor( colors[0] );
      tft.print( oldPower );
      tft.setCursor( 0, 180 );
      tft.setTextColor( colors[colorCounter] );
      oldPower = "";
      oldPower.concat(  String(px_eData.WSV) + " Volts" );
      //oldPower.concat(  String(px_eData.WSV) + "V " + String(int(px_eData.WSC * 1000.0f)) + "mA " + String((int(px_eData.WSP * 1000.0f))) + "mW" );
      tft.println( oldPower );
      colorCounter++;
      if ( colorCounter > (numOfColors - 1) )
      {
        colorCounter = 1;
      }
      Tick = !Tick;
      //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
    } //if ( xQueueReceive(xQ_eData, &px_eData, portMAX_DELAY) == pdTRUE )
  } //for (;;)
  vTaskDelete( NULL );
} //void fDoTheDisplayTHing( void * parameter )
////
void fmqttWatchDog( void * paramater )
{
  int UpdateImeTrigger = 86400; //seconds in a day
  int UpdateTimeInterval = 86300; // 1st time update in 100 counts
  int maxNonMQTTresponse = 5;
  for (;;)
  {
    vTaskDelay( 1000 );
    if ( mqttOK >= maxNonMQTTresponse )
    {
      ESP.restart();
    }
    xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
    mqttOK++;
    xSemaphoreGive( sema_mqttOK );
    UpdateTimeInterval++; // trigger new time get
    if ( UpdateTimeInterval >= UpdateImeTrigger )
    {
      TimeSet = false; // sets doneTime to false to get an updated time after a days count of seconds
      UpdateTimeInterval = 0;
    }
  }
  vTaskDelete( NULL );
}
////
float fCalulate_IAQ_Index( int gasResistance, float Humidity)
{
  float hum_baseline = 40.0f;
  float hum_weighting = 0.25f;
  float gas_offset = 0.0f;
  float hum_offset = 0.0f;
  float hum_score = 0.0f;
  float gas_score = 0.0f;
  gas_offset = oGasResistanceBaseLine - float( gasResistance );
  hum_offset = float( Humidity ) - hum_baseline;
  // calculate hum_score as distance from hum_baseline
  if ( hum_offset > 0.0f )
  {
    hum_score = 100.0f - hum_baseline - hum_offset;
    hum_score /= ( 100.0f - hum_baseline );
    hum_score *= ( hum_weighting * 100.0f );
  } else {
    hum_score = hum_baseline + hum_offset;
    hum_score /= hum_baseline;
    hum_score *= ( 100.0f - (hum_weighting * 100.0f) );
  }
  //calculate gas score as distance from baseline
  if ( gas_offset > 0.0f )
  {
    gas_score = float( gasResistance ) / oGasResistanceBaseLine;
    gas_score *= ( 100.0f - (hum_weighting * 100.0f ) );
  } else {
    gas_score = 100.0f - ( hum_weighting * 100.0f );
  }
  return ( hum_score + gas_score );
} //void fCalulate_IAQ_Index( int gasResistance, float Humidity):
////
void fDoParticleDetector( void * parameter )
{
  /*
    ug/m3     AQI                 Lvl AQ (Air Quality)
    (air Quality Index)
    0-35     0-50                1   Excellent
    35-75    51-100              2   Average
    75-115   101-150             3   Light pollution
    115-150  151-200             4   moderate
    150-250  201-300             5   heavy
    250-500  >=300               6   serious
  */
  float ADbits = 4095.0f;
  float uPvolts = 3.3f;
  float adcValue = 0.0f;
  float dustDensity = 0.0f;
  float Voc = 0.6f; // Set the typical output voltage, when there is zero dust.
  const float K = 0.5f; // Use the typical sensitivity in units of V per 100ug/m3.
  xEventGroupWaitBits (eg, evtWaitForBME, pdTRUE, pdTRUE, portMAX_DELAY );
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 100; //delay for mS
  for (;;)
  {
    //enable sensor led
    gpio_set_level( GPIO_NUM_4, HIGH ); // set gpio 4 to high to turn on sensor internal led for measurement
    esp_timer_start_once( oneshot_timer, 280 ); // trigger one shot timer for a 280uS timeout, warm up time.
    xEventGroupWaitBits (eg, evtDoParticleRead, pdTRUE, pdTRUE, portMAX_DELAY ); // event will be triggered by the timer expiring, wait here for the 280uS
    adcValue = float( adc1_get_raw(ADC1_CHANNEL_0) ); //take a raw ADC reading from the dust sensor
    gpio_set_level( GPIO_NUM_4, LOW );//Shut off the sensor LED
    adcValue = ( adcValue * uPvolts ) / ADbits; //calculate voltage
    dustDensity = (adcValue / K) * 100.0; //convert volts to dust density
    if ( dustDensity < 0.0f )
    {
      dustDensity = 0.00f; // make negative values a 0
    }
    if ( xSemaphoreTake( sema_PublishPM, 0 ) == pdTRUE )  // don't wait for semaphore to be available
    {
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
      //log_i( "ADC volts %f Dust Density = %ug / m3 ", adcValue, dustDensity ); // print the calculated voltage and dustdensity
      MQTTclient.publish( topicInsidePM, String(dustDensity).c_str() );
      xSemaphoreGive( sema_MQTT_KeepAlive );
      x_eData.PM2 = dustDensity;
    }
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
    //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
  }
  vTaskDelete( NULL );
}// end fDoParticleDetector()
////
void DoTheBME680Thing( void *pvParameters )
{
  SPI.begin(); // initialize the SPI library
  vTaskDelay( 10 );
  if (!bme.begin()) {
    log_i("Could not find a valid BME680 sensor, check wiring!");
    while (1);
  }
  // Set up oversampling and filter initialization
  bme.setTemperatureOversampling(BME680_OS_8X);
  bme.setHumidityOversampling(BME680_OS_2X);
  bme.setPressureOversampling(BME680_OS_4X);
  bme.setIIRFilterSize(BME680_FILTER_SIZE_3);
  bme.setGasHeater(320, 150); // 320*C for 150 ms
  //wait for a mqtt connection
  while ( !MQTTclient.connected() )
  {
    vTaskDelay( 250 );
  }
  xEventGroupSetBits( eg, evtWaitForBME );
  TickType_t xLastWakeTime    = xTaskGetTickCount();
  const TickType_t xFrequency = 1000 * 15; //delay for mS
  String bmeInfo = "";
  bmeInfo.reserve( 100 );
  for (;;)
  {
    x_eData.Temperature  = bme.readTemperature();
    x_eData.Temperature  = ( x_eData.Temperature * 1.8f ) + 32.0f; // (Celsius x 1.8) + 32
    x_eData.Pressure     = bme.readPressure();
    x_eData.Pressure     = x_eData.Pressure / 133.3223684f; //converts to mmHg
    x_eData.Humidity     = bme.readHumidity();
    x_eData.IAQ          = fCalulate_IAQ_Index( bme.readGas(), x_eData.Humidity );
    //log_i( " temperature % f, Pressure % f, Humidity % f IAQ % f", x_eData.Temperature, x_eData.Pressure, x_eData.Humidity, x_eData.IAQ);
    bmeInfo.concat( String(x_eData.Temperature, 2) );
    bmeInfo.concat( "," );
    bmeInfo.concat( String(x_eData.Pressure, 2) );
    bmeInfo.concat( "," );
    bmeInfo.concat( String(x_eData.Humidity, 2) );
    bmeInfo.concat( "," );
    bmeInfo.concat( String(x_eData.IAQ, 2) );
    xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY );
    if ( MQTTclient.connected() )
    {
      MQTTclient.publish( topicInsideInfo, bmeInfo.c_str() );
    }
    xSemaphoreGive( sema_MQTT_KeepAlive );
    xSemaphoreGive( sema_PublishPM ); // release publish of dust density
    xSemaphoreTake( sema_mqttOK, portMAX_DELAY );
    mqttOK ++;
    xSemaphoreGive( sema_mqttOK );
    xQueueOverwrite( xQ_eData, (void *) &x_eData );// send data to display
    //
    bmeInfo = ""; // empty the string buffer
    findDewPointWithHumidity( x_eData.Humidity, x_eData.Temperature );
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
    // log_i( "DoTheBME280Thing high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
  }
  vTaskDelete ( NULL );
}
////
/*
  Important to not set vTaskDelay/vTaskDelayUntil to less then 10. Errors begin to develop with the MQTT and network connection.
  makes the initial wifi/mqtt connection and works to keeps those connections open.
*/
void MQTTkeepalive( void *pvParameters )
{
  sema_MQTT_KeepAlive   = xSemaphoreCreateBinary();
  xSemaphoreGive( sema_MQTT_KeepAlive ); // found keep alive can mess with a publish, stop keep alive during publish
  MQTTclient.setKeepAlive( 90 ); // setting keep alive to 90 seconds makes for a very reliable connection, must be set before the 1st connection is made.
  TickType_t xLastWakeTime = xTaskGetTickCount();
  const TickType_t xFrequency = 250; //delay for ms
  for (;;)
  {
    //check for a is-connected and if the WiFi 'thinks' its connected, found checking on both is more realible than just a single check
    if ( (wifiClient.connected()) && (WiFi.status() == WL_CONNECTED) )
    {
      xSemaphoreTake( sema_MQTT_KeepAlive, portMAX_DELAY ); // whiles MQTTlient.loop() is running no other mqtt operations should be in process
      MQTTclient.loop();
      xSemaphoreGive( sema_MQTT_KeepAlive );
    }
    else {
      log_i( "MQTT keep alive found MQTT status % s WiFi status % s", String(wifiClient.connected()), String(WiFi.status()) );
      if ( !(wifiClient.connected()) || !(WiFi.status() == WL_CONNECTED) )
      {
        connectToWiFi();
      }
      connectToMQTT();
    }
    //log_i( " high watermark % d",  uxTaskGetStackHighWaterMark( NULL ) );
    xLastWakeTime = xTaskGetTickCount();
    vTaskDelayUntil( &xLastWakeTime, xFrequency );
  }
  vTaskDelete ( NULL );
}
////
void connectToMQTT()
{
  byte mac[5]; // create client ID from mac address
  WiFi.macAddress(mac); // get mac address
  String clientID = String(mac[0]) + String(mac[4]) ; // use mac address to create clientID
  while ( !MQTTclient.connected() )
  {
    MQTTclient.connect( clientID.c_str(), mqtt_username, mqtt_password );
    vTaskDelay( 250 );
  }
  MQTTclient.setCallback( mqttCallback );
  MQTTclient.subscribe  ( topicOK );
  MQTTclient.subscribe  ( topicRemainingMoisture_0 );
  MQTTclient.subscribe  ( topicWindSpeed );
  MQTTclient.subscribe  ( topicWindDirection );
  MQTTclient.subscribe  ( topicRainfall );
  MQTTclient.subscribe  ( topicWSVolts );
  MQTTclient.subscribe  ( topicWSCurrent );
  MQTTclient.subscribe  ( topicWSPower );
  MQTTclient.subscribe  ( topicDPnWI );
} //void connectToMQTT()
void connectToWiFi()
{
  int TryCount = 0;
  while ( WiFi.status() != WL_CONNECTED )
  {
    TryCount++;
    WiFi.disconnect();
    WiFi.begin( SSID, PASSWORD );
    vTaskDelay( 4000 );
    if ( TryCount == 10 )
    {
      ESP.restart();
    }
  }
  WiFi.onEvent( WiFiEvent );
}
////
float findDewPointWithHumidity( float humi, float temperature )
{
  //Celcius
  float ans =  (temperature - (14.55 + 0.114 * temperature) * (1 - (0.01 * humi)) - pow(((2.5 + 0.007 * temperature) * (1 - (0.01 * humi))), 3) - (15.9 + 0.117 * temperature) * pow((1 - (0.01 * humi)), 14));
  //log_i( "%f", ans );
  return ans;
}
void loop() { }
////

The #define evtDoParticleRead ( 1 << 0 ) // declare an event sets up an event group trigger that will be used by the timer to stop and start program execution.

In setup the timer is initialzed with:

// High Resolution Timer - ESP32 - — ESP-IDF Programming Guide latest documentation High Resoultion Timer API
esp_timer_create_args_t oneshot_timer_args = {}; // initialize High Resoulition Timer (HRT) configuration structure
oneshot_timer_args.callback = &oneshot_timer_callback; // configure for callback, name of callback function
esp_timer_create( &oneshot_timer_args, &oneshot_timer ); // assign configuration to the HRT, receive timer handle

Also, in setup the evengt group is initialized.

On this line the timer is started, esp_timer_start_once( oneshot_timer, 280 ); // trigger one shot timer for a 280us timeout, warm up time.

After the timer is started the event group wait stops code execution till given the go ahead.
xEventGroupWaitBits (eg, evtDoParticleRead, pdTRUE, pdTRUE, portMAX_DELAY ); // event will be triggered by the timer expiring, wait here for the 280uS

In void IRAM_ATTR oneshot_timer_callback( void* arg ) the timer callback, this line xEventGroupSetBitsFromISR( eg, evtDoParticleRead, &xHigherPriorityTaskWoken ); sets the event group wait bit.

Once the event group wait bit is set the task is released and executes the rest of the code.

Thanks everyone for the quick replies :slight_smile:
I need 3 SPWM signals, 120 degrees out of phase, and their inverted signals. So a total of 6 signals. But I need to have a delay of 1us in between each signal and its inverted signal.

Post your code (or a minimally functional example) and let us know what Arduino platform or processor you're using.

Hey thanks for the reply. But I need the delay inside an ISR. Can I Call another ISR from an ISR? If so, where can I get such an ISR having 1us delay?

Thanks in advance :slight_smile:

16 NOPs?

If you need 1uS I'd recommend inlining a few inconsequential assembly code commands like:

ISR( ... )
{
    <do stuff>
    //delay 1uS
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");
    __asm__("nop\n\t");

    <do more stuff>
}

This

sounds too strange to me. Take a Teensy 4.0. Should be fast enough.

Arduino SPWM Generator Circuit - Code Details and Diagram - Homemade Circuit Projects (homemade-circuits.com)

Hi,

What is the application?
What are you applying this 6ch signal too?
Do you need sine or squarewave signals?

Can you post a diagram of the 6ch outputs you need?

Thanks.. Tom... :grinning: :+1: :coffee: :australia:

Thanks everyone for the replies. So here is my requirement: I need 3 SPWM signals which are 120 degrees out of phase to each other, and their inverted signals. But the original wave and its corresponding inverted wave should have a time delay of 1us in between them. eg., phase 1 and inverted phase 1 signal should have a delay of 1 us. similarly for phase 2 and phase 3.
For this I got a code from Arduino forum which is given below. But in the code, Timer 0 is disabled and so delay(), millis() etc won't work. But I did not understand why Timer 0 is disabled. I think there is no need of disabling it. So can I comment out this line, so that I can use delay() and millis()? Should I add anything else to the code to enable timer 0?

So here is the code:
/*
*

  • DDS Sine Generator mit ATMEGS 328
  • Timer2 generates the 31250 KHz Clock Interrupt
  • Use Timer2 Interrupt to change duty cycle for the output PWM signals
  • D. Tolken
  • 120 degress out of phase signals for 3 phase BLDC motor controller
  • CPUT, South Africa

a Huge thumbs up and thanks must be given to Martin Nawrath for the developement of the original code to generate a sine wave using PWM and a LPF.
Link:
http://interface.khm.de/index.php/lab/experiments/arduino-dds-sinewave-generator/
*/

#include "avr/pgmspace.h" //Store data in flash (program) memory instead of SRAM

// Look Up table of a single sine period divied up into 256 values. Refer to PWM to sine.xls on how the values was calculated
PROGMEM prog_uchar sine256 = {
127,130,133,136,139,143,146,149,152,155,158,161,164,167,170,173,176,178,181,184,187,190,192,195,198,200,203,205,208,210,212,215,217,219,221,223,225,227,229,231,233,234,236,238,239,240,
242,243,244,245,247,248,249,249,250,251,252,252,253,253,253,254,254,254,254,254,254,254,253,253,253,252,252,251,250,249,249,248,247,245,244,243,242,240,239,238,236,234,233,231,229,227,225,223,
221,219,217,215,212,210,208,205,203,200,198,195,192,190,187,184,181,178,176,173,170,167,164,161,158,155,152,149,146,143,139,136,133,130,127,124,121,118,115,111,108,105,102,99,96,93,90,87,84,81,78,
76,73,70,67,64,62,59,56,54,51,49,46,44,42,39,37,35,33,31,29,27,25,23,21,20,18,16,15,14,12,11,10,9,7,6,5,5,4,3,2,2,1,1,1,0,0,0,0,0,0,0,1,1,1,2,2,3,4,5,5,6,7,9,10,11,12,14,15,16,18,20,21,23,25,27,29,31,
33,35,37,39,42,44,46,49,51,54,56,59,62,64,67,70,73,76,78,81,84,87,90,93,96,99,102,105,108,111,115,118,121,124

};
#define cbi(sfr, bit) (_SFR_BYTE(sfr) &= ~_BV(bit)) //define a bit to have the properties of a clear bit operator
#define sbi(sfr, bit) (_SFR_BYTE(sfr) |= _BV(bit))//define a bit to have the properties of a set bit operator

int PWM1= 11;// PWM1 output, phase 1
int PWM2 = 3; //[WM2 ouput, phase 2
int PWM3 = 10; //PWM3 output, phase 3
int offset_1 = 85; //offset 1 is 120 degrees out of phase with previous phase, Refer to PWM to sine.xls
int offset_2 = 170; //offset 2 is 120 degrees out of phase with offset 1. Refer to PWM to sine.xls
int program_exec_time = 6; //monitor how quickly the interrupt trigger
int ISR_exec_time = 7; //monitor how long the interrupt takes

double dfreq;
const double refclk=31376.6; // measured output frequency

// variables used inside interrupt service declared as voilatile
volatile byte current_count; // Keep track of where the current count is in sine 256 array
volatile byte ms4_delay; //variable used to generate a 4ms delay
volatile byte c4ms; // after every 4ms this variable is incremented, its used to create a delay of 1 second
volatile unsigned long phase_accumulator; // pahse accumulator
volatile unsigned long tword_m; // dds tuning word m, refer to DDS_calculator (from Martin Nawrath) for explination.

void setup()
{
pinMode(PWM1, OUTPUT); //sets the digital pin as output
pinMode(PWM2, OUTPUT); //sets the digital pin as output
pinMode(PWM3, OUTPUT); //sets the digital pin as output
pinMode(program_exec_time, OUTPUT); //sets the digital pin as output
pinMode(9, OUTPUT); //sets the digital pin as output
sbi(PORTD,program_exec_time); //Sets the pin
Setup_timer1();
Setup_timer2();

//Disable Timer 1 interrupt to avoid any timing delays
cbi (TIMSK0,TOIE0); //disable Timer0 !!! delay() is now not available
sbi (TIMSK2,TOIE2); //enable Timer2 Interrupt

dfreq=1000.0; //initial output frequency = 1000.o Hz
tword_m=pow(2,32)*dfreq/refclk; //calulate DDS new tuning word

}
void loop()
{
while(1)
{
sbi(PORTD,program_exec_time); //Sets the pin
if (c4ms > 250) // c4ms = 4ms, thus 4ms *250 = 1 second delay
{
c4ms=0; //Reset c4ms
dfreq=analogRead(0); //Read voltage on analog 1 to see desired output frequency, 0V = 0Hz, 5V = 1.023kHz
cbi (TIMSK2,TOIE2); //Disable Timer2 Interrupt
tword_m=pow(2,32)*dfreq/refclk; //Calulate DDS new tuning word
sbi (TIMSK2,TOIE2); //Enable Timer2 Interrupt
}
}
}

//Timer 1 setup
//Set prscaler to 1, PWM mode to phase correct PWM, 16000000/510 = 31372.55 Hz clock
void Setup_timer1(void)
{
// Timer1 Clock Prescaler to : 1
sbi (TCCR1B, CS10);
cbi (TCCR1B, CS11);
cbi (TCCR1B, CS12);

// Timer1 PWM Mode set to Phase Correct PWM
cbi (TCCR1A, COM1A0);
sbi (TCCR1A, COM1A1);
cbi (TCCR1A, COM1B0);
sbi (TCCR1A, COM1B1);

// Mode 1 / Phase Correct PWM
sbi (TCCR1A, WGM10);
cbi (TCCR1A, WGM11);
cbi (TCCR1B, WGM12);
cbi (TCCR1B, WGM13);
}

//Timer 1 setup
//Set prscaler to 1, PWM mode to phase correct PWM, 16000000/510 = 31372.55 Hz clock
void Setup_timer2()
{
// Timer2 Clock Prescaler to : 1
sbi (TCCR2B, CS20);
cbi (TCCR2B, CS21);
cbi (TCCR2B, CS22);

// Timer2 PWM Mode set to Phase Correct PWM
cbi (TCCR2A, COM2A0); // clear Compare Match
sbi (TCCR2A, COM2A1);
cbi (TCCR2A, COM2B0);
sbi (TCCR2A, COM2B1);

// Mode 1 / Phase Correct PWM
sbi (TCCR2A, WGM20);
cbi (TCCR2A, WGM21);
cbi (TCCR2B, WGM22);
}

//Timer2 Interrupt Service at 31372,550 KHz = 32uSec
//This is the timebase REFCLOCK for the DDS generator
//FOUT = (M (REFCLK)) / (2 exp 32)
//Runtime : 8 microseconds
ISR(TIMER2_OVF_vect)
{
cbi(PORTD,program_exec_time); //Clear the pin
sbi(PORTD,ISR_exec_time); // Sets the pin

phase_accumulator=phase_accumulator+tword_m; //Adds tuning M word to previoud phase accumulator. refer to DDS_calculator (from Martin Nawrath) for explination.
current_count=phase_accumulator >> 24; // use upper 8 bits of phase_accumulator as frequency information

OCR2A=pgm_read_byte_near(sine256 + current_count); // read value fron ROM sine table and send to PWM
OCR2B=pgm_read_byte_near(sine256 + (uint8_t)(current_count + offset_1)); // read value fron ROM sine table and send to PWM, 120 Degree out of phase of PWM1

OCR1A = pgm_read_byte_near(sine256 + (uint8_t)(current_count + offset_2));// read value fron ROM sine table and send to PWM, 120 Degree out of phase of PWM2
OCR1B = pgm_read_byte_near(sine256 + (uint8_t)(current_count + offset_2));// read value fron ROM sine table and send to PWM, 120 Degree out of phase of PWM2

//increment variable ms4_delay every 4mS/125 = milliseconds 32uS
if(ms4_delay++ == 125)
{
c4ms++;
ms4_delay=0; //reset count
}

cbi(PORTD,ISR_exec_time); //Clear the pin
}

@gourie how many more times ?

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