ESP32 Forum

Posted: **Sun Mar 19, 2023 11:50 am**

I bought a Heltec Wifi Kit 32 V3
When the board arrived, it was working well, wifi and screen.
I uploaded the classic blink and everithing was ok.

Now it was time to make the OLED work,
i've worked with them before but it was with an arduino pro micro,
after uploading the example, nothing worked, tested around and this is what i know:
- the board boots
- nothing appears on screen
- the board resets when any `Heltec.display` method is called

need some help solving this

When calling any `Heltec.display` method this appears on the serial monitor
```
ELF file SHA256: fd4d2b96ec26363e

Rebooting...
ESP-ROM:esp32s3-20210327
Build:Mar 27 2021
rst:0xc (RTC_SW_CPU_RST),boot:0x8 (SPI_FAST_FLASH_BOOT)
Saved PC:0x420218fa
SPIWP:0xee
mode:DIO, clock div:1
load:0x3fce3808,len:0x44c
load:0x403c9700,len:0xbe4
load:0x403cc700,len:0x2a38
entry 0x403c98d4
Serial initial done
Guru Meditation Error: Core 1 panic'ed (LoadProhibited). Exception was unhandled.

Core 1 register dump:
PC : 0x420016bf PS : 0x00060630 A0 : 0x82001675 A1 : 0x3fcebe20
A2 : 0x00000000 A3 : 0x00000001 A4 : 0x00000000 A5 : 0x00000001
A6 : 0x00000001 A7 : 0x1c03a180 A8 : 0x820016b9 A9 : 0x3fcebdd0
A10 : 0x00000003 A11 : 0x00000003 A12 : 0x00000000 A13 : 0x0000002c
A14 : 0x0000002b A15 : 0x0000e100 SAR : 0x00000010 EXCCAUSE: 0x0000001c
EXCVADDR: 0x00000018 LBEG : 0x400556d5 LEND : 0x400556e5 LCOUNT : 0xfffffffa

Backtrace: 0x420016bc:0x3fcebe20 0x42001672:0x3fcebe40 0x42002a9a:0x3fcebe60
```

Posted: **Sun May 21, 2023 3:20 pm**

Hi,

I had the same issue with the Heltec library. In the end after reading several posts I ditched the Heltec libs and used:

thingpulse/ESP8266 and ESP32 OLED driver for SSD1306 displays@^4.4.0

Also the Heltec docs are terrible and the schematic has the wrong pins as far as I can tell.

Here is the code which worked for me.

Code: Select all

#include "SSD1306.h"        
#define OLED_I2C_ADDRESS 0x3c
#define OLED_SDA 4
#define OLED_SCL 15
#define OLED_RST 16

SSD1306 display(OLED_I2C_ADDRESS, OLED_SDA, OLED_SCL);

void setup_display()
{

    // Manually reset the screen
    pinMode(OLED_RST, OUTPUT);
    digitalWrite(OLED_RST, LOW);
    delay(200);
    digitalWrite(OLED_RST, HIGH);

    display.init();
    display.flipScreenVertically();
    display.clear();
    display.setFont(ArialMT_Plain_16);
    display.drawString(0, 0, text);
    display.display();
}

Hope this helps

ESP32 Forum

Heltec WIFI Kit 32 V3 OLED

Heltec WIFI Kit 32 V3 OLED

Re: Heltec WIFI Kit 32 V3 OLED