Help with the Heltec 'Stick'

[rpiboy-79]

As noted previously new to the world of Arduino and micro-electronics.

Have been able to get demo programs running on our 'Stick' just fine, and we even wrote our own app that creates synthetic temp/humidity data and successfully sends it to an MQTT broker via WiFi. All good! However, we went to install/use an actual DHT22 with no luck, verified that the DHT22 is fine via a Pi and GPIO interface. We took a step back and tried to make an external LED blink based on some basic code from a GPIO project kit, and again, no luck. Serial and Display print the right values. Clearly I'm having an issue either with pin assignments, or voltage (I think?). Here is the test code we tried, which we get no LED blinking. Yes there is a resistor inline with the LED and yes we used Gemini to convert Python to C++. Hoping that by posting here it will reach an audience already familiar with the Heltec boards.

Help greatly appreciated! Thanks in advance.

#define HELTEC_WIRELESS_STICK
#include <heltec_unofficial.h>


/*
  Blink_ESP32.ino
  Description: Basic usage of GPIO on ESP32. Let LED blink.
  Author: www.freenove.com (modified for ESP32)
  Modification: 2023/10/27
*/

const int ledPin = 47;
void setup() {
  heltec_setup();
  pinMode(ledPin, OUTPUT);
  Serial.begin(115200); // ESP32 often uses 115200 baud rate
  Serial.println("ESP32 Blink program starting...");
  both.print("Both: ESP32 Blink program starting...");
}

void loop() {
  heltec_loop();
  digitalWrite(ledPin, HIGH);
  Serial.println("LED turned on");
  both.print("Both: LED turned on");
  delay(1000);

  digitalWrite(ledPin, LOW);
  Serial.println("LED turned off");
  both.print("Both: LED turned off");
  delay(1000);
}

[rpiboy-79]

Here is the code we wrote for using the DHT22, as noted previously this code worked fine with simulated data, but we can't read data from the sensor.

#include <WiFi.h>
#include <PubSubClient.h>
#include <Wire.h>  
#include "HT_SSD1306Wire.h"
#include "Adafruit_GFX.h"
#include "driver/gpio.h"
#include <Arduino.h>
#include "DHT.h"




// Define the display object - IMPORTANT!
SSD1306Wire factory_display(0x3c, 500000, SDA_OLED, SCL_OLED, GEOMETRY_64_32, RST_OLED);

// WiFi credentials
const char* ssid = "***";
const char* password = "***";
const char* hostName = "ESP32_DHT22_DEMO";

// MQTT broker details
const char* mqttServer = "192.168.***"; 
const int mqttPort = 1883; // Default MQTT port
const char* mqttUser = "***"; // Optional
const char* mqttPassword = "***"; // Optional
const char* mqttTopic = "dht22-data"; // The topic to publish to

WiFiClient espClient;
PubSubClient client(espClient);

// DHT22 sensor settings
#define DHTPIN 3
#define DHTTYPE DHT22
DHT dht(DHTPIN, DHTTYPE);

// Function to read data from DHT22 sensor
float readTemperature() {
    float t = dht.readTemperature();
    if (isnan(t)) {
        Serial.println(F("Failed to read from DT sensor!"));
        return NAN;
    }
    return t;
}

//float readHumidity() {
  //  float h = dht.readHumidity();
    //if (isnan(h)) {
      //  Serial.println(F("Failed to read from DH sensor!"));
        //return NAN;
    //}
    //return h;
//}


void setup() {
  Serial.begin(115200);
  WiFi.setHostname(hostName);
  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(1000);
    Serial.print(".");
  }
  Serial.println("Connected to WiFi");

  client.setServer(mqttServer, mqttPort);
  client.setCallback(callback); // For subscribing (if needed later)

  // Initialize OLED display 
  VextON();
  delay(100);
  factory_display.init();
  factory_display.clear();
  factory_display.display();
  factory_display.drawString(0, 0, "Starting Up");
}

void VextON(void){
  pinMode(Vext,OUTPUT);
  digitalWrite(Vext, LOW);
}

void loop() {
  factory_display.clear();
  factory_display.display();
  
  if (!client.connected()) {
    reconnect();
  }
  client.loop(); // Important for maintaining the connection

    // Read the actual data from the DHT22 sensor
    float temperature = readTemperature();
    float humidity = 0;//readHumidity();
    if (!isnan(temperature) && !isnan(humidity)) {

      // Create the JSON payload (recommended for easier parsing)
      String jsonPayload = "{";
      jsonPayload += "\"temperature\": " + String(temperature) + ",";
      jsonPayload += "\"humidity\": " + String(humidity) + "}";

      // Publish the data to the MQTT broker
      client.publish(mqttTopic, jsonPayload.c_str());

      Serial.print("Published: ");
      Serial.println(jsonPayload);
      String message = "Data Sent:";
      message += "\nTemp: " + String(temperature) + "\nHumidity: " + String(humidity);
      factory_display.clear();
      factory_display.drawString(0, 0, message);
      factory_display.display();

      delay(10000); // Send data every 5 seconds (adjust as needed)
    }
    else {
      String messageFail = "Failure to read sensor data";
      Serial.print(messageFail);
      factory_display.clear();
      factory_display.drawString(0, 0, messageFail);
      factory_display.display();
      delay(10000);
    }
}


void reconnect() {
  while (!client.connected()) {
    Serial.print("Connecting to MQTT...");
    factory_display.clear();
    factory_display.drawString(0, 0, "Connecting to MQTT");
    factory_display.display();
    if (client.connect("ESP32Client", mqttUser, mqttPassword)) { // Client ID, username, and password
      Serial.println("connected");
      factory_display.clear();
      factory_display.drawString(0, 0, "connected");
      factory_display.display();
      // Subscribe to topics here if needed (e.g., client.subscribe("some/topic"));
    } 
    else {
      Serial.print("failed, rc=");
      factory_display.clear();
      factory_display.drawString(0, 0, "Connection Failed");
      factory_display.display();
      Serial.print(client.state());
      Serial.println(" try again in 5 seconds");
      factory_display.clear();
      factory_display.drawString(0, 0, "Try again in 5 seconds");
      factory_display.display();
      delay(5000);
    }
  }
}

void callback(char* topic, byte* message, unsigned int length) {
  // This function is called when a message is received on a subscribed topic.
  // You won't need it for *publishing* data, but it's here for completeness if you
  // want to add subscribing functionality later.
  Serial.print("Message arrived [");
  Serial.print(topic);
  Serial.print("] ");
  for (int i = 0; i < length; i++) {
    Serial.print((char)message[i]);
  }
  Serial.println();
}

[StevenCellist]

I see there's a whole bunch of Serial output being generated - what is it that you actually see there?

And also, how have you wired up your DHT22 pins?

[rpiboy-79]

The serial outputs were/are for debugging, particularly as I did not have the display working immediately and even then have not dug into how to get the display to 'scroll' long text, or re-write the print statements with refreshes to get the full message onto the display.

Wiring, it is a 3 pin DHT22, ground to one of the grounds (don't recall which) voltage to the 3.3v pin and then I tried multiple GPIO pins with no success.

[StevenCellist]

I understand the Serial is for debugging, but can you share the actual output from that? That way we can see what exactly works and what doesn't ;)

[rpiboy-79]

Oh sorry! I mis-understood. Everything prints as expected, with the exception that when it attempts to read the data from the sensor it says:

Here is the initial output, it did eventually connect to the MQTT server once I brought it back online. Once it connects, it just starts looping though the failure message.

ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0x1 (POWERON),boot:0x8 (SPI_FAST_FLASH_BOOT)
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce2820,len:0x1188
load:0x403c8700,len:0x4
load:0x403c8704,len:0xbf0
load:0x403cb700,len:0x30e4
entry 0x403c88ac
...Connected to WiFi
Connecting to MQTT...failed, rc=-2 try again in 5 seconds
 
Failure to read sensor dataFailed to read from DT sensor!
Failure to read sensor data

[gaetanoelia]

Come mai usi la libreria un_official se non stai usando Lora? Ti consiglio di disinstallare dal tuo IDE quella libreria e installare quella ufficiale Heltec. Molti PIN GPIO della libreria ufficiale sono diversi, e alcuni non funzionanti su quella Non Ufficiale. Scusami scrivo Italiano, rispondo dal telefono adesso. Buon lavoro.

[rpiboy-79]

The code above actually doesn't presently use the un-official library. I found my way here looking for assistance from folks that might be familiar with the Heltec board, rather than posting on generic forums. If there are suggestions on where I can get help from folks with more experience working with the Heltec boards that would be great! Otherwise, if there any suggestions on what I'm missing trying to get a simple Temp/Humidity sensor running I'd greatly appreciate it!