OLED I2c Display With Arduino

zeus2kx · May 11, 2017, 5:04pm

Hello Guys,
I followed this article to start working with Oleds.
It works great!

Now I am trying to add a sensor and display the output on the screen:

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_SSD1306.h>
int sensorPin = A0;   
int sensorValue = 0; 
float Vout=0;
float P=0;
float Ppa=0;

#define OLED_RESET 4
Adafruit_SSD1306 display(OLED_RESET);

void setup()   {                
  Serial.begin(9600);
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  }


void loop() {  
  display.display();
  delay(1000);
    display.clearDisplay();   // Clear the buffer.
int i=0;
  int sum=0;
  int offset=0;
  Serial.println("init...");
  for(i=0;i<10;i++)
  {
    sensorValue = analogRead(sensorPin)-512;
    sum+=sensorValue;
    }

    offset=sum/10.0;
    while(1)
    {
       sensorValue = analogRead(sensorPin)-offset; 
       Vout=(5*sensorValue)/1023.0;
       P=(Vout-2.5)/0.285;
       Ppa = P*1000;          
       Serial.print("Pressure = " );                       
       Serial.print(Ppa); 
       Serial.println("Pa");
       Serial.print("Vout = " );                       
       Serial.print(Vout); 
       Serial.println("V");
       display.setTextSize(2);
       display.setTextColor(WHITE);
       display.setCursor(0,20);
       display.println("Pres: ");
       display.setCursor(60,20);
       display.println((float)Ppa);
       display.setCursor(0,40);
       display.println("Vout: ");
       display.setCursor(60,40);
       display.println((float)Vout);
       display.display();
       delay(1000);
       display.clearDisplay();  
    }
}

I have an issue:

Adafruit logo from the previous article doesn’t go away even after uploading above code.
How can I get rid of it?

Thanks in advance.

Z

zeus2kx · May 11, 2017, 6:32pm

someone?

david_prentice · May 11, 2017, 7:05pm

The logo is hard coded into the buffer in the Library CPP. Just change the initialisation data to your picture. Or omit the assignment completely. Then it will default to all 0x00.

The subject has come up before.

David.

zeus2kx · May 11, 2017, 8:22pm

david_prentice:
Or omit the assignment completely.

David.

Thanks for reply.
I solved the problem by writing my own logo, but I would be interested in knowing how to get rid of it.

How can I do that?

Did you mean:

const unsigned char PROGMEM logo [] = {0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00
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};

Z

david_prentice · May 11, 2017, 8:37pm

Go on. It is pretty obvious:

static uint8_t buffer[SSD1306_LCDHEIGHT * SSD1306_LCDWIDTH / 8] = {
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
...
};

instead you use:

static uint8_t buffer[SSD1306_LCDHEIGHT * SSD1306_LCDWIDTH / 8];

AS you have probably realised, display.display() will show whatever is in the buffer.
Although you start off with the Adafruit image, as soon as you call clearDisplay() it clears the buffer.

You need a susbequent display.display() to see the result.

David.

zeus2kx · May 11, 2017, 9:00pm

Great, thanks. It will certainly help.

Another thing I noticed that right after repowering, OLED displays white dots (like in old days when CRT TVs had no signal), for about a sec and then logo appears.

Can you tell me is there a way around?

Thanks again.

david_prentice · May 11, 2017, 9:30pm

Most controllers have their own on-chip RAM. It contains random data at power-up. It retains memory when the controller is asleep or the controller is reset.

If you don’t want to see the random memory, initialise the RAM before you turn the display on.

In practice, simply display.clearDisplay() and display.display() as soon as you begin.

David.

zeus2kx · May 11, 2017, 10:02pm

david_prentice:
In practice, simply display.clearDisplay() and display.display() as soon as you begin.

I will try that tomorrow.

Thanks again.

system · May 6, 2021, 3:49am