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Understanding "SSD1306 allocation failure" - Arduino Nano Old bootloader-Adafruit SSD1306 library

robogary

Understanding "SSD1306 allocation failure" - Arduino Nano Old bootloader - using ADAfruit library 

My latest ongoing project uses a ssd1306 OLED as a message board to display values of temperature sensors, status messages, alarms, etc..

The project is going well, becoming an obsession, adding useful features and ideas, however I kept banging into times where the latest code additions wouldn't execute fully, some IO wouldn't update, and extreme cases where the SSD1306 totally stopped working after an upload of new code.

I'd have to go backward to the previous working code to fix.  The IDE compilation errors window had no errors.

I did eventually discover the "SSD1306 allocation failed " message in the serial monitor.

This is one section of the code that calls to display data to the SSD1306:

float DHT11_humidity= dht11.readHumidity();
// read temperature as Celsius
float DHT11tempC = dht11.readTemperature();
// read temperature as Fahrenheit
float DHT11tempF = dht11.readTemperature(true);

// check if any reads failed
if (isnan(DHT11_humidity) || isnan(DHT11tempC) || isnan(DHT11tempF)) {
Serial.println("Failed to read from DHT11 sensor!");
}

/// display readings to the SSD1306 OLED /////
display.clearDisplay();
delay(ScreenClearDelay);
display.setCursor(0, 10);
// Display static text
display.println("Humidity");
display.println(" %");
display.println(DHT11_humidity);
display.display();
delay(ScreenOnTime);// for reading display


display.clearDisplay();
delay(ScreenClearDelay);
display.setCursor(0, 10);
// Display static text
display.println(" DHT11");
display.println("temp F=");
display.println(DHT11tempF);
display.display();
delay(ScreenOnTime);// for reading display

ScreenOnTime is 3000msec. ScreenClearDelay is 250 msec. 

The program had  11 to 13 information screens like this printed to SSD1306 using more code just like this portion.  

After commenting out an extraneous SSD1306 screen prints, new code was able to be added and IO working. 

There is some limit to how many times the SSD1306 can be called upon to display info, or what can be displayed. 

The allocation message seems more of "can the SSD1306 talk to the address 0x3C" than not enough room for all this simple text. I did see one hint in the Arduino forum to suggest removing SSD1306 screens from the code to avoid this allocation message.

Looking for advice for understanding exactly what the library message is, quantify the number of text screens or memory needed ( which maybe can lead to me to make the code more efficient ), or understand if to change the platform from the old Nano to a newer Arduino with more memory.  

  • I wasn't really sure what you mean.

    By 'screens' do you mean some sort of windowing inside the physical display, or do you mean you've got multiple physical displays attached to the Arduino? If the latter, you're using multiple I2C interfaces (and if so, are these software I2C interfaces or something?).

    Also, if you can share your code, then maybe some opportunities for reducing resource usage can be identified (e.g. closing I2C interfaces if there is no display updating going on, if you're using many physical displays).

  • in reply to shabaz

    Thanks, Altho I tried to be clear and succinct in posting the question, reading it again after your feedback, agree the question had vague babble to it  :-) The question has been edited to hopefully make it more intelligible..... maybe.

  • in reply to robogary

    Unfortunately there's not enough info. Your code snippet is missing the function that could cause the allocation failed message (something like display.begin()), so I can't tell where and how many times it's called, to try to figure out why resources are not available.

    Also, regarding this part:

    "After commenting out an extraneous SSD1306 screens"

    By screens, are you referring to multiple physical SSD1306 display modules connected to the Arduino?

  • in reply to shabaz

    My bad, I'm calling the print code snippet as a screen. 

    There is only one physical SSD1306 device. 

    Aw crap. The display.begin is in void setup. That little detail was provided in the original question, but somehow got deleted. I'll add it back in when I get my PC fired up again. 

  • I think you are using adafruit SSD306 library, in which this function return an error if the buffer memory allocation fails.

    bool Adafruit_SSD1306::begin(uint8_t vcs, uint8_t addr, bool reset,
bool periphBegin) {

if ((!buffer) && !(buffer = (uint8_t *)malloc(WIDTH * ((HEIGHT + 7) / 8))))
return false;


    as you are using Arduino nano which has only 2Kb ram, which is not sufficient for multiple screens.