void loop () ending erratically

Good morning to all,
before anything else I want to say that I'm a beginner and I'm simply having fun with Arduino and the like.
I feel a bit embarrassed to post this because I'm afraid it's just a stupid thing I'm fighting with, due to my lack of experience.
In any case, here is the problem.
I'm playing with an OLED display ( 1.30", 132 x 64, SH1106 driven) and I'm trying to have a vertically scrolling text. The program is developed on Arduino but, when complete, it will be ported to an Heltec WiFi-Kit-32 where I have a barometer program, with static display, which runs smoothly .

Now, the simple text scroll program runs in a very erratic way:
on Arduino Nano it goes on forever
on Arduino UNO it runs for 10-12 complete scroll cycles and then freezes
on Arduino Mega it runs for 1-2 complete scroll cycles and then freezes.

It's quite weird and I'm sure there is a simple reason behind it but I cannot figure it out.

has anybody any explanation for such behaviour?

Many thanks in advance

 *  Fabrizio M. Bianchi 19 - January - 2021
 *  Test program to have a vertically scrolling text on an OLED display 
 *  initially developed on an Arduino but meant for ESP32 based modules
 *  For some still unknown reason the void loop runs for a few cycles on Arduino Mega and it stops casuallly, 
 *  for some tens of cycles on the UNO and on the NANO  .
 *  Display : 1.3" - 128 x 60
 *  Color : White
 *  Driver : SH1106 ( SSD1306 for Heltec WiFi-Kit-32)
 *  Connectivity : I2C default pins (A4 and A5 for Uno, D20 and D21 for Mega2560

#include <Wire.h>
#include <U8g2lib.h>

int line;
// Display Constructor for the 0,96" embedded display on Heltec WiFi-Kit-32
// U8G2_SSD1306_128X64_NONAME_F_HW_I2C   u8g2(U8G2_R0, 16, 15, 4);

// Display Constructor for 1.30" display with SH1106

U8G2_SH1106_128X64_NONAME_F_HW_I2C u8g2(U8G2_R0,/*reset*/U8X8_PIN_NONE);

void setup() {

// Graphic Library Initialization


void loop() {
  for (line = 0; line <=64; line = line += 8) {
      u8g2.drawStr(24, line, "Barometro");
      u8g2.drawStr(24, (line + 18), "Pressione");

Is the display 5V compatible? If no, do you have 3.3V-5V signal translation?

the display is 3.3V and powered by the 3.3V pin of each Arduino I've tried (Uno, Nano, Mega)

My apologies, I misunderstood your question.
Actually not, there is no level translation from the two output pins (SDA and SCL) of the Arduino and the OLED display.

Darn! I've forgotten another bit of info. The display module is 5V compatible as it has an on-board voltage regulator from 5V to 3.3V

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