OLED display behaves strangely

Projects Programming
1

Dear friends, currently I am working on an ultrasound-"radar" project. An ultrasound sensor swipes over a certain angle with the help of a stepper motor, reads distances and a tiny little OLED display is supposed to show the "environment" graphically. I know there exist a million similar projects out there with code and all but I wanted to make it by myself. (I just "borrowed" the declaration part.) I broke it into different tasks and managed to get the stepper and the ultrasound sensor working well. Just the display behaves strangely. It is an SSD1306 0.96" IIC. I tested different small things first. When I write code like:

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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define linelength 40
#define x1_line 64
#define y1_line 60
#define wait 100

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
}
}

void loop() {
  // put your main code here, to run repeatedly:

display.clearDisplay();
display.display();

display.drawLine(64,64,10,10,WHITE);
display.display();
delay(50);
display.clearDisplay();
display.drawLine(64,64,7,10,WHITE);
display.display();
delay(50);
display.clearDisplay();
display.drawLine(64,64,15,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();

display.drawLine(64,64,30,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,45,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,60,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,75,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,90,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,105,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();
display.drawLine(64,64,128,10,WHITE);
display.display();
delay(wait);
display.clearDisplay();

delay(5);
}

it works well and shows, the display is able to show many lines one after the other. This was only a preliminary test. Now I wanted to "let the beam swipe over the display" with the help of a for loop. It still is not connected to the stepper or sensor, it is still just a display test:

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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels
#define linelength 40
#define x1_line 64
#define y1_line 60
#define wait 100

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     -1 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);


void setup() {
  // put your setup code here, to run once:
Serial.begin(9600);

if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;);
}
}

void loop() {
  // put your main code here, to run repeatedly:

display.clearDisplay();
display.display();
for (int i= (-45); i<45; i=i+5){
   display.clearDisplay();
   delay(wait);
   int angle = i + 90; // turn graphics around by 90 degrees
   int i_rad = angle*PI/180;
   int x2_line = x1_line+(linelength * cos(i_rad)); //polar to cartesian coordinates
   int y2_line = y1_line-(linelength * sin(i_rad));
   
   display.drawLine(x1_line,y1_line,x2_line,y2_line,WHITE);
   display.display();
   Serial.println(i);
   delay(wait);
   }
delay(5);
}

I expected a "swipe motion" with 5 degree steps but I only got three lines roughly 57(=1 rad?) degrees from each other. They appear one after the other and then get cleared and it starts over again. On the serial monitor I get good 5 degree readings for i. What do I miss?

2

everything is correct, you calculate radians in integers, and there are only 3 radians in 180 degrees.
Try to define i_rad variable as float

3

Thank you so much b707! Seems I was just one hair away from the solution (1 rad) but you spotted it right away. Now with float i_rad the code works. Now I can go on and build the stuff. Thank you!

4

Please mark the thread as solved if got the answer

6

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