Error compiling for board WEMOS LOLIN32

Compiling a simple sketch for WEMOS LOLIN32 board I get an error message that doesn’t seem to refer to anything in the code.


#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 64
#define DISPLAY_RESET 4       // Reset pin # (or -1 if sharing Arduino reset pin)
#define SCREEN_ADDRESS 0x3D   // 0x3D for 128x64, 0x3C for 128x32


void setup()
  Wire.begin(5, 4);       // I2C comms on ports SDA=5, SCL=4 on OLED

  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if (!display.begin(SSD1306_SWITCHCAPVCC, 0x3C, false, false)) // Address for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for (;;);            // Don't proceed, loop forever

  static const uint8_t code_Array[8][16] =
    {0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87, 0x88, 0x89, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F},
    {0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97, 0x98, 0x99, 0x8A, 0x8B, 0x8C, 0x8D, 0x8E, 0x8F},
    {0xA0, 0xA1, 0xA2, 0xA3, 0xA4, 0xA5, 0xA6, 0xA7, 0xA8, 0xA9, 0xAA, 0xAB, 0xAC, 0xAD, 0xAE, 0xAF},
    {0xB0, 0xB1, 0xB2, 0xB3, 0xB4, 0xB5, 0xB6, 0xB7, 0xB8, 0xB9, 0xBA, 0xBB, 0xBC, 0xBD, 0xBE, 0xBF},
    {0xC0, 0xC1, 0xC2, 0xC3, 0xC4, 0xC5, 0xC6, 0xC7, 0xC8, 0xC9, 0xCA, 0xCB, 0xCC, 0xCD, 0xCE, 0xCF},
    {0xD0, 0xD1, 0xD2, 0xD3, 0xD4, 0xD5, 0xD6, 0xD7, 0xD8, 0xD9, 0xDA, 0xDB, 0xDC, 0xDD, 0xDE, 0xDF},
    {0xE0, 0xE1, 0xE2, 0xE3, 0xE4, 0xE5, 0xE6, 0xE7, 0xE8, 0xE9, 0xEA, 0xEB, 0xEC, 0xED, 0xEE, 0xEF},
    {0xF0, 0xF1, 0xF2, 0xF3, 0xF4, 0xF5, 0xF6, 0xF7, 0xF8, 0xF9, 0xFA, 0xFB, 0xFC, 0xFD, 0xfE, 0xFF}

  display.setCursor(0, 0);  
  for (uint8_t i = 0; i <= 8; i++)
    for (uint8_t j = 0; j <= 16; j++)

Error message:

Arduino: 1.8.13 (Windows 10), Board: "WEMOS LOLIN32, 80MHz, Default, 240MHz (WiFi/BT), 921600"

C:\Users\hans\AppData\Local\Temp\arduino_cache_375079\core\core_600365080b52ab60b0924f16600e23b6.a(main.cpp.o):(.literal._Z8loopTaskPv+0x4): undefined reference to `loop()'
C:\Users\hans\AppData\Local\Temp\arduino_cache_375079\core\core_600365080b52ab60b0924f16600e23b6.a(main.cpp.o): In function `loopTask(void*)':
C:\Users\hans\AppData\Local\Arduino15\packages\esp32\hardware\esp32\1.0.4\cores\esp32/main.cpp:17: undefined reference to `loop()'
collect2.exe: error: ld returned 1 exit status
exit status 1
Error compiling for board WEMOS LOLIN32.

You have to put

void loop()

Even if it's empty

undefined reference to `loop()'

You didn't define the loop() function. If you don't need it, make it an empty function: void loop() {}


You have to put

void loop()


Even if it's empty

Thank you. What an simple mistake.

This topic was automatically closed 120 days after the last reply. New replies are no longer allowed.