ESP32 Cheap Yellow Display (CYD) Pinout (ESP32-2432S028R)

11 thoughts on “ESP32 Cheap Yellow Display (CYD) Pinout (ESP32-2432S028R)”

1. I have sniffed at this gadget several times, and always come away with the feeling that there is simply too little GPIO available for it to be of any use to me. It is certainly of no use for robotics-like projects with heaps of motors, sensors, actuators and things. I haven’t bothered with detailed pin count but suspect very many GPIO pins remain inaccessible.

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2. These devices make good clock / sensor displays.
   I have used BME280, HTU21D, AHT10, Si7021, and DS18B20 sensors successfully on I2C using the following pins:
   #define OneWirePin 27
   #define I2C_SCL 22
   #define I2C_SDA 27
   They display data, broadcast telemetry (MQTT), and post to SQL database. Using the LDR the display can automatically dim with the ambient light.
   They are also handy for remote buttons using MQTT for controlling various things like flood lights.
   The ones with the “C” connector need a capacitor across the reset button to automatically flash in the Arduino IDE. Thank you for your previous article about dealing with that problem.

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   • Correction, the DS18B20 sensor was on OneWire not I2C. I just use the same pins and connector. My devices check for the DS18B20 then each of the other sensors until it finds one. That way changing sensors only requires a reboot. I will post the code if anyone is interested in it.

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     • Yes the Code please.

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       • /*
         // Global Variables

         char SB2[7], ST2[7], SH2[7];
         float B(NAN), T(NAN), H(NAN);

         const PROGMEM char bmeLabel[] = “BME”;
         const PROGMEM char htuLabel[] = “HTU”;
         const PROGMEM char ahtLabel[] = “AHT”;
         const PROGMEM char siLabel[] = “SI”;
         const PROGMEM char dsLabel[] = “DS”;
         const PROGMEM char xxxLabel[] = “XXX”;

         const PROGMEM char bmeMsg[] = “BME280 sensor found”;
         const PROGMEM char htuMsg[] = “HTU21D sensor found”;
         const PROGMEM char ahtMsg[] = “AHT10 sensor found”;
         const PROGMEM char siMsg[] = “Si7021 sensor found”;
         const PROGMEM char dsMsg[] = “DS18B20 sensor found”;
         const PROGMEM char xxxMsg[] = “Sensor not found.”;

         BME280I2C bme;
         BME280::TempUnit tempUnit(BME280::TempUnit_Fahrenheit);
         BME280::PresUnit presUnit(BME280::PresUnit_inHg);
         Adafruit_HTU21DF htu = Adafruit_HTU21DF();
         Adafruit_Si7021 Si = Adafruit_Si7021();
         OneWire oneWire1(OneWirePin);
         DallasTemperature sensorsDS(&oneWire1);
         AHT10 aht(AHT10_ADDRESS_0X38);

         */

         void initSensors() {
         // timerWrite(Timer, 0);
         // byte addrArray[8];
         Serial.println();
         // DS18B20 sensors can be found either by search or count
         sensorsDS.begin();
         // if (oneWire1.search(addrArray)) {
         int ds1 = sensorsDS.getDeviceCount();
         // Serial.printf(“DS Sensor Count = %u\n”, ds1);
         if (ds1 > 0) {
         MQTTclient.publish(topic_D, dsMsg);
         Serial.println(dsMsg);
         strcpy(sensor, dsLabel);
         } else {
         Wire.begin(I2C_SDA, I2C_SCL); // must start wire after checking for DS18B20 sensor <== necesary because default pins are not used
         if (Si.begin()) {
         MQTTclient.publish(topic_D, siMsg);
         Serial.println(siMsg);
         strcpy(sensor, siLabel);
         } else {
         if (htu.begin()) {
         MQTTclient.publish(topic_D, htuMsg);
         Serial.println(htuMsg);
         strcpy(sensor, htuLabel);
         } else {
         if (aht.begin()) {
         MQTTclient.publish(topic_D, ahtMsg);
         Serial.println(ahtMsg);
         strcpy(sensor, ahtLabel);
         } else {
         if (bme.begin()) {
         MQTTclient.publish(topic_D, bmeMsg);
         Serial.println(bmeMsg);
         strcpy(sensor, bmeLabel);
         } else {
         strcpy(sensor, xxxLabel);
         MQTTclient.publish(topic_D, xxxMsg);
         Serial.println(xxxMsg);
         Wire.end();
         }
         }
         }
         }
         }
         Serial.println();
         }

         void readSensor() {
         // timerWrite(Timer, 0);
         if (strcmp(sensor, bmeLabel) == 0) readBME();
         else if (strcmp(sensor, htuLabel) == 0) readHTU();
         else if (strcmp(sensor, ahtLabel) == 0) readAHT();
         else if (strcmp(sensor, siLabel) == 0) readSi();
         else if (strcmp(sensor, dsLabel) == 0) readDS();
         }

         void readAHT() {
         char tmp[7];
         T = aht.readTemperature();
         H = aht.readHumidity();
         T = 1.8 * T + 32.0;
         dtostrf(T, 5, 1, tmp);
         StripSpaces(7, ST2, tmp);
         dtostrf(H, 5, 1, tmp);
         StripSpaces(7, SH2, tmp);
         }

         void readBME() {
         char tmp[7];
         bme.read(B, T, H, tempUnit, presUnit);
         dtostrf(B, 5, 1, tmp);
         StripSpaces(7, SB2, tmp);
         dtostrf(T, 5, 1, tmp);
         StripSpaces(7, ST2, tmp);
         dtostrf(H, 5, 1, tmp);
         StripSpaces(7, SH2, tmp);
         }

         void readHTU() {
         char tmp[7];
         T = htu.readTemperature();
         T = 1.8 * T + 32.0;
         dtostrf(T, 5, 1, tmp);
         StripSpaces(7, ST2, tmp);
         H = htu.readHumidity();
         dtostrf(H, 5, 1, tmp);
         StripSpaces(7, SH2, tmp);
         }

         void readSi() {
         char tmp[7];
         T = Si.readTemperature();
         T = 1.8 * T + 32.0;
         dtostrf(T, 5, 1, tmp);
         StripSpaces(7, ST2, tmp);
         H = Si.readHumidity();
         dtostrf(H, 5, 1, tmp);
         StripSpaces(7, SH2, tmp);
         }

         void readDS() {
         int tpr;
         char tmp[7];
         sensorsDS.setWaitForConversion(true);
         sensorsDS.requestTemperatures();
         //delay(40);
         T = sensorsDS.getTempFByIndex(0); // first sensor found
         dtostrf(T, 5, 1, tmp);
         StripSpaces(7, ST2, tmp);
         }

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         • I forgot to include this function used in the above.

           void StripSpaces(int len, char* output, char* input) {
           // accept either byte or char
           int j = 0;
           for (int i = 0; i < len; i++) {
           if (input[i] != 32) {
           if(input[i] == 0) break;
           output[j] = char(input[i]);
           j++;
           }
           output[j] = 0;
           }
           input[len-1] = 0;
           }

           Of course, you may not need both floating point and text versions of the data so you could just delete those parts.

         • Sorry, I also forgot the library includes:

           #include <Wire.h>
           #include <BME280I2C.h>
           #include <Adafruit_HTU21DF.h>
           #include <Adafruit_Si7021.h>
           #include <OneWire.h>
           #include <DallasTemperature.h>
           #include <AHT10.h>

     • Yes please. Looking to do something similar.

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3. There is a branch of TFT_eSPI that has been modified for 2 SPI busses. I have been using it in all my projects. I especially like being able to use the touch_calibrate function from the demo. It provides fast concise calibration for each display. I wish Bodmer would adopt this for the master version.
   You can find it here:
   https://github.com/maxpautsch/TFT_eSPI

   The following lines need to be in the USER_SETUP file:
   #define SOFTSPI // Uncomment for software SPI
   #define TOUCH_CS 33 // Chip select pin (T_CS) of touch screen
   #define TOUCH_MOSI 32 // Separate Touch SoftSPI bus
   #define TOUCH_MISO 39 // Separate Touch SoftSPI bus
   #define TOUCH_CLK 25 // Separate Touch SoftSPI bus
   #define TOUCH_INT 36
   #define TOUCH_IRQ 36

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4. Has anyone done anything with going into sleep on this board, what sort of mA do you down to for light sleep, or deep sleep?

   And how do you turn off display eyc, just with CS?

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5. As usual, very good article.
   Meanwhile, GPIO 16 is used both for SPI (TFT_MISO) and the green led ?

   I tested to switch on/off the leds and the green one is mapped to GPIO 16.
   I tried to set TFT_MISO to GPIO 16 and the TFT works !

   Meanwhile, if you want to use the green LED and both the TFT, you will have to define TFT_MISO to something else (I tried 12, 16, 19 and either 21 !). Of course, if you use pin 12, you won’t be able to use TFT_RST.

   Starting from the default example: https://randomnerdtutorials.com/cheap-yellow-display-esp32-2432s028r/

   I added these definitions:
   #define PIN_LED_R 4
   #define PIN_LED_G 16
   #define PIN_LED_B 17

   And then this method :
   void animateLed(int pinNumber) {
   digitalWrite(pinNumber, LOW);
   delay(500);
   digitalWrite(pinNumber, HIGH);
   delay(500);
   }

   In the setup method, before initializing, set the leds pin mode:
   pinMode(PIN_LED_R, OUTPUT);
   pinMode(PIN_LED_G, OUTPUT);
   pinMode(PIN_LED_B, OUTPUT);

   and finally, in the loop method, animate the leds:

   animateLed(PIN_LED_R);
   animateLed(PIN_LED_G);
   animateLed(PIN_LED_B);

   Finally, in the printTouchToSerial method, add the TFT pins definition to make sure what is User_Setup.h file is used:
   Serial.println(“————————————————-“);
   Serial.print(“TFT_MISO: “);
   Serial.println(TFT_MISO);
   Serial.print(“TFT_MOSI: “);
   Serial.println(TFT_MOSI);
   Serial.print(“TFT_SCLK: “);
   Serial.println(TFT_SCLK);
   Serial.print(“TFT_CS: “);
   Serial.println(TFT_CS);
   Serial.print(“TFT_DC: “);
   Serial.println(TFT_DC);
   Serial.print(“TFT_RST: “);
   Serial.println(TFT_RST);
   Serial.println(“————————————————-“);

   If TFT_MISO is set to 16 (same as green led), the TFT will work but the led not.
   If TFT_MISO is set to something else, both will work, and displaying the TFT_MISO pin like it is defined in the User_Setup.h file :

   X = 262 | Y = 193 | Pressure = 2675

   TFT_MISO: 12
   TFT_MOSI: 13
   TFT_SCLK: 14
   TFT_CS: 15
   TFT_DC: 2

   TFT_RST: -1

   How is it possible that the TFT_MISO can change to other pin ?
   I do not understand.

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