ESP32: ULP LED Hart beat and read DHT22 sensor

ESP32-ULP-Blink-DHT22.ino

/*
  Blink ULP Hartbeat and read DHT22 in ULP code

  Tom Vijlbrief oct 2017
*/

#include <time.h>
#include <sys/time.h>

#include "driver/rtc_io.h"
#include <driver/adc.h>
#include <esp_adc_cal.h>

#include "esp32/ulp.h"
#include "soc/rtc_cntl_reg.h"
#include "soc/sens_reg.h"
#include "soc/rtc.h"

#include "esp_sleep.h"
#include "esp_err.h"

#include <WiFi.h>
#include <WiFiUdp.h>

#include "wifi-pw.h" // My network and password

// WiFi network name and password:
const char * networkName = NETWORK;
const char * networkPswd = PASSWORD;

const gpio_num_t gpio_led = GPIO_NUM_2;
const gpio_num_t gpio_dht = GPIO_NUM_32;
const gpio_num_t gpio_builtin = GPIO_NUM_22;

const int V_REF= 1117;

//IP address to send UDP data to:
// either use the ip address of the server or
// a network broadcast address
const char * udpAddress = "192.168.0.9";
const int udpPort = 41234;

//Are we currently connected?
boolean connected = false;

//The udp library class
WiFiUDP udp;

uint64_t chipid;

RTC_DATA_ATTR int bootCount = 0;

/*
   Offset (in 32-bit words) in RTC Slow memory where the data is placed
   by the ULP coprocessor. It can be chosen to be any value greater or equal
   to ULP program size, and less than the CONFIG_ULP_COPROC_RESERVE_MEM/4 - 6,
   where 6 is the number of words used by the ULP coprocessor.
*/
#define ULP_DATA_OFFSET     200
#define FLASH_CNT           0
#define DATA_CNT            1
#define ADC                 2
#define TEMP_OFFSET         100
#define RH_OFFSET           200


/**
   @brief Utility function which reads data written by ULP program

   @param offset offset from ULP_DATA_OFFSET in RTC Slow memory, in words
   @return lower 16-bit part of the word writable by the ULP
*/
static inline uint16_t ulp_data_read(size_t offset)
{
  return RTC_SLOW_MEM[ULP_DATA_OFFSET + offset] & 0xffff;
}

/**
   @brief Utility function which writes data to be ready by ULP program

   @param offset offset from ULP_DATA_OFFSET in RTC Slow memory, in words
   @param value lower 16-bit part of the word to be stored
*/
static inline void ulp_data_write(size_t offset, uint16_t value)
{
  RTC_SLOW_MEM[ULP_DATA_OFFSET + offset] = value;
}

void connectToWiFi(const char * ssid, const char * pwd){
  Serial.println("Connecting to WiFi network: " + String(ssid));

  // delete old config
  WiFi.disconnect(true);
  //register event handler
  WiFi.onEvent(WiFiEvent);

  //Initiate connection
  WiFi.begin(ssid, pwd);

  Serial.println("Waiting for WIFI connection...");
}

//wifi event handler
void WiFiEvent(WiFiEvent_t event){
    switch(event) {
      case SYSTEM_EVENT_STA_GOT_IP:
          //When connected set
          Serial.print("WiFi connected! IP address: ");
          Serial.println(WiFi.localIP());
          //initializes the UDP state
          //This initializes the transfer buffer
          udp.begin(WiFi.localIP(),udpPort);
          connected = true;
          break;
      case SYSTEM_EVENT_STA_DISCONNECTED:
          Serial.println("WiFi lost connection");
          connected = false;
          break;
      default:
          break;
    }
}

void setup() {

  pinMode(gpio_builtin, OUTPUT);
  digitalWrite(gpio_builtin, LOW);

  Serial.begin(115200);

  chipid= ESP.getEfuseMac(); // The chip ID is essentially its MAC address(length: 6 bytes)

  if (bootCount) return;

#if 0
  Serial.println("Measure VREF at GPIO 25");
  esp_err_t status = adc2_vref_to_gpio(GPIO_NUM_25);
  if (status != ESP_OK) {
      Serial.println("failed to route v_ref\n");
  }
  delay(10000);
#endif

  if (!rtc_gpio_is_valid_gpio(gpio_led) || !rtc_gpio_is_valid_gpio(gpio_dht))
    Serial.println("Bad IO");
  rtc_gpio_init(gpio_led);
  rtc_gpio_set_direction(gpio_led, RTC_GPIO_MODE_OUTPUT_ONLY);
  //rtc_gpio_set_drive_capability(gpio_led, GPIO_DRIVE_CAP_DEFAULT);
  //rtc_gpio_hold_dis(gpio_num);

  rtc_gpio_init(gpio_dht);
  rtc_gpio_set_direction(gpio_dht, RTC_GPIO_MODE_INPUT_ONLY);

  //rtc_gpio_pullup_en(gpio_dht);

#if 1
  ulp_data_write(FLASH_CNT, 0);
  ulp_data_write(DATA_CNT, 0);

  const ulp_insn_t program[] = {
    // load data offset into R2
    I_MOVI(R2, ULP_DATA_OFFSET),

    I_LD(R1, R2, FLASH_CNT), // increment counter
    I_ADDI(R1, R1, 1),
    I_ST(R1, R2, FLASH_CNT),

#if 1
    I_ANDI(R0, R1, 0x3FFF),
    M_BXZ(6), // Read sensor data
#endif

    M_LABEL(0),
    I_ANDI(R1, R1, 0xFFFF), // Wakeup?
    M_BXZ(5),

    I_ANDI(R1, R1, 0x3FF),
    M_BXZ(1), // long interval between 2 hartbeats

    I_SUBI(R3, R1, 1),
    M_BXZ(3), // first beat

    I_SUBI(R3, R1, 2),
    M_BXZ(4), // dark between first and second beat

    I_SUBI(R3, R1, 40), // second beat
    M_BXZ(3),

    M_LABEL(1),
   // I_SLEEP_CYCLE_SEL(0), // 2s

    M_LABEL(2),
    I_WR_REG_BIT(RTC_IO_TOUCH_PAD2_REG, RTC_IO_TOUCH_PAD2_HOLD_S, 0), // HOLD off
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0), // RTC_GPIO_12 == GPIO_02, LED off
    I_WR_REG_BIT(RTC_GPIO_OUT_W1TC_REG,RTC_GPIO_OUT_DATA_W1TC_S+12,1),

    I_WR_REG_BIT(RTC_IO_TOUCH_PAD2_REG, RTC_IO_TOUCH_PAD2_HOLD_S, 1), // HOLD on
    I_HALT(),

    M_LABEL(3), // turn LED on
    I_WR_REG_BIT(RTC_IO_TOUCH_PAD2_REG, RTC_IO_TOUCH_PAD2_HOLD_S, 0), // HOLD off
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1),
    I_WR_REG_BIT(RTC_GPIO_OUT_W1TS_REG,RTC_GPIO_OUT_DATA_W1TS_S+12,1),

    I_WR_REG_BIT(RTC_IO_TOUCH_PAD2_REG, RTC_IO_TOUCH_PAD2_HOLD_S, 1), // HOLD on
    //I_SLEEP_CYCLE_SEL(1), // 10ms

    // stop the ULP program
    I_HALT(),

    M_LABEL(4),
    //I_SLEEP_CYCLE_SEL(2), // 100ms
    M_BX(2), // led OFF

    // Wakeup
    M_LABEL(5),

    I_END(),
    I_WAKE(),
    I_HALT(),

    M_LABEL(6),
#if 1
#if 1 // Read DHT22

    // Pull low for 1.5ms
    I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 9, 0),
    // Output mode
    I_WR_REG_BIT(RTC_GPIO_ENABLE_W1TS_REG, RTC_GPIO_ENABLE_W1TS_S + 9, 1), // RTC_GPIO_9 == GPIO_32
    I_MOVI(R0, 0),
    M_LABEL(7),
    I_ADDI(R0,R0,1),
    M_BL(7,1500),

    // Input mode:
    I_WR_REG_BIT(RTC_GPIO_ENABLE_W1TC_REG, RTC_GPIO_ENABLE_W1TC_S + 9, 1), // RTC_GPIO_9 == GPIO_32

    // Wait for sensor pull down, with time out
    I_MOVI(R3,100),
    M_LABEL(8),
    I_SUBI(R3,R3,1),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    M_BXZ(0), // Time out
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    M_BGE(8,1),

    // Wait for sensor pull up
    M_LABEL(9),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    M_BL(9,1),

    // Start of data loop
    I_MOVI(R1,16), // read 16 bits
    I_MOVI(R2,0), // shift data bits into R2

    // Wait for sensor pull down
    M_LABEL(10),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    M_BGE(10,1),

    // Wait for sensor pull up
    M_LABEL(11),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    M_BL(11,1),

    // Now measure time to next pull down
    I_MOVI(R3,0),
    M_LABEL(12),
    I_ADDI(R3,R3,1),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    M_BGE(12,1),

    // 40 loops is a 1 bit, 14 loops is a 0 bit, update current slot
    I_LSHI(R2, R2, 1),
    I_RSHI(R3,R3,5), // 32 or more loops
    I_ORR(R2,R2,R3),

    I_SUBI(R1,R1,1),
    I_MOVR(R0,R1),
    M_BGE(10,1), // Get next bit

    I_MOVR(R3, R2), // Save result in R3
    I_MOVI(R2, ULP_DATA_OFFSET), // restore R2

    I_LD(R0, R2, DATA_CNT), // load measurement counter

    // Save current measurement
    I_ADDR(R0, R0, R2),
    I_ST(R3, R0, RH_OFFSET),

    // Now repeat for temperature data:

    // Start of data loop
    I_MOVI(R1,16), // read 16 bits
    I_MOVI(R2,0), // shift data bits into R2

    // Wait for sensor pull down
    M_LABEL(20),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    M_BGE(20,1),

    // Wait for sensor pull up
    M_LABEL(21),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    //I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 1), I_WR_REG_BIT(RTC_GPIO_OUT_REG, RTC_GPIO_OUT_DATA_S + 12, 0),
    M_BL(21,1),

    // Now measure time to next pull down
    I_MOVI(R3,0),
    M_LABEL(22),
    I_ADDI(R3,R3,1),
    I_RD_REG(RTC_GPIO_IN_REG, RTC_GPIO_IN_NEXT_S + 9, RTC_GPIO_IN_NEXT_S + 9),
    M_BGE(22,1),

    // 40 loops is a 1 bit, 14 loops is a 0 bit, update current slot
    I_LSHI(R2, R2, 1),
    I_RSHI(R3,R3,5), // 32 or more loops
    I_ORR(R2,R2,R3),

    I_SUBI(R1,R1,1),
    I_MOVR(R0,R1),
    M_BGE(20,1), // Get next bit

    I_MOVR(R3, R2), // Save result in R3
    I_MOVI(R2, ULP_DATA_OFFSET), // restore R2

    I_LD(R0, R2, DATA_CNT), // increment measurement counter
    I_ADDI(R0, R0, 1),
    I_ST(R0, R2, DATA_CNT),

    // Save current measurement
    I_ADDR(R0, R0, R2),
    I_ST(R3, R0, TEMP_OFFSET-1),

    // Resume main hartbeat loop
    I_LD(R1, R2, FLASH_CNT), // Restore counter to R1

#else // Read internal sensor

    I_LD(R0, R2, DATA_CNT), // increment counter
    I_ADDI(R0, R0, 1),
    I_ST(R0, R2, DATA_CNT),

    // enable temperature sensor
    I_WR_REG(SENS_SAR_MEAS_WAIT2_REG, SENS_FORCE_XPD_SAR_S, SENS_FORCE_XPD_SAR_S + 1, 3),
    // do temperature measurement and store result in R3
    I_TSENS(R3, 8000),
    // disable temperature sensor
    I_WR_REG(SENS_SAR_MEAS_WAIT2_REG, SENS_FORCE_XPD_SAR_S, SENS_FORCE_XPD_SAR_S + 1, 0),
    // Save current measurement
    I_ADDR(R0, R0, R2),
    I_ST(R3, R0, TEMP_OFFSET-1),
#endif
#endif

    M_BX(0),
  };

  // Load ULP program into RTC_SLOW_MEM, at offset 0
  size_t size = sizeof(program) / sizeof(ulp_insn_t);
  ESP_ERROR_CHECK( ulp_process_macros_and_load(0, program, &size) );
  assert(size < ULP_DATA_OFFSET && "ULP_DATA_OFFSET needs to be greater or equal to the program size");

  // Set ULP wakeup periods
  REG_WRITE(SENS_ULP_CP_SLEEP_CYC0_REG, rtc_clk_slow_freq_get_hz() / 180); // About 5ms
//  REG_WRITE(SENS_ULP_CP_SLEEP_CYC1_REG, rtc_clk_slow_freq_get_hz() / 180); // About 5ms LED on
//  REG_WRITE(SENS_ULP_CP_SLEEP_CYC2_REG, rtc_clk_slow_freq_get_hz() / 10); // About 100ms hartbeat interval

#endif
}


void loop()
{
  Serial.print("Boot:  "); Serial.println(bootCount);
  Serial.print("Flash: "); Serial.println(ulp_data_read(FLASH_CNT));
  int cnt= ulp_data_read(DATA_CNT);
  Serial.print("Data:  "); Serial.println(cnt);

//  for (int i= 0; i < cnt; ++i) {
//    Serial.print(ulp_data_read(RH_OFFSET+i)); Serial.print(' ');
//    Serial.println(ulp_data_read(TEMP_OFFSET+i));
//  }
  ulp_data_write(DATA_CNT, 0);

//  for (int i= 0; i < 8; i++) {
//      Serial.print("adc: "); Serial.println(ulp_data_read(ADC+i));
//  }

  if (true || (bootCount & 0x3) == 0) {

      //Connect to the WiFi network
      connectToWiFi(networkName, networkPswd);

      adc1_config_width(ADC_WIDTH_12Bit);
      adc1_config_channel_atten(ADC1_CHANNEL_6,ADC_ATTEN_11db);
      // Calculate ADC characteristics i.e. gain and offset factors
      esp_adc_cal_characteristics_t characteristics;
      esp_adc_cal_get_characteristics(V_REF, ADC_ATTEN_11db, ADC_WIDTH_12Bit, &characteristics);

      // Read ADC and obtain result in mV
      uint32_t milliVolt = adc1_to_voltage(ADC1_CHANNEL_6, &characteristics);
      //int milliVolt = adc1_get_raw(ADC1_CHANNEL_6) * int(1100 * 3.6) / 4095;
      Serial.print("milliVolt: "); Serial.println(milliVolt);

      //only send data when connected
      while (!connected) {
          Serial.print(".");
          delay(100);
      }

      String str;
      for (int i= 0; i < cnt; ++i) {
          str+= ulp_data_read(TEMP_OFFSET+i); str+= ' ';
          str+= ulp_data_read(RH_OFFSET+i); str+= ' ';
      }
      Serial.println(str);

      RTC_DATA_ATTR static time_t prev, now;
      time(&now);
      time_t diff= now-prev;
      prev= now;
      Serial.println(diff);

      //Send a packet
//      udp.beginPacket(udpAddress,udpPort);
//      udp.printf("%u %u %u %u %u %lu %s", (uint32_t)chipid,
//             !cnt ? 210 : ulp_data_read(TEMP_OFFSET+cnt-1),
//             milliVolt,
//             !cnt ? 500 : ulp_data_read(RH_OFFSET+cnt-1),
//             cnt, diff, str.c_str());
//
//      udp.endPacket();
      delay(10);
  }

  ++bootCount;

  time_t now;
  struct tm timeinfo;
  time(&now);
  localtime_r(&now, &timeinfo);

  char strftime_buf[64];

  setenv("TZ", "UTC", 1);
  tzset();
  localtime_r(&now, &timeinfo);
  strftime(strftime_buf, sizeof(strftime_buf), "%c", &timeinfo);
  Serial.print("The current date/time is: ");
  Serial.println(strftime_buf);

  //if (rtc_gpio_set_level(gpio_dht, bootCount & 1) != ESP_OK)
  //    Serial.println("Error!");
  //rtc_gpio_hold_en(gpio_led);
  //esp_sleep_enable_timer_wakeup(10 * 1000000);
  //esp_sleep_pd_config(ESP_PD_DOMAIN_RTC_PERIPH, ESP_PD_OPTION_ON);

  // Start ULP
  //if (bootCount == 1)
      ESP_ERROR_CHECK( ulp_run(0) );
  esp_sleep_enable_ulp_wakeup();
  esp_deep_sleep_start();
}

Hi,
I'd like to know, if you ever found a workaround for the problem of this complex ULP-Programs, stop working after a while (https://www.esp32.com/viewtopic.php?t=3183)???
I found the same problem and it looks like, the wakeup mechanism is sometimes not working (like the timer is not starting at I_HALT()).
It's a pitty, but this way, the ULP is not reliable.

BR
Guido

@gdampf, did you resolve the ulp reliability issue? thanks, m

@mahesh2000, following the description in the link from my last post, I got it working without WiFi by disabling the I_END(), but this may not be satisfying in all cases. I decided, to do it without ULP, but deep sleep between the measures, so I managed to have my Sensor sending in 10 min. intervals powered by a small rechargeable battery for about 2 months, which is fine. But, of course, I get only 6 samples per hour this way. For temperature and humidity, this nevertheless is exact enough in most cases.

hi @gdampf, do you mean that you kept the ULP running in sleep/wake cycles forever without restarting it? that would work for me.