VDO code

Hey everyone!

I have a VDO Oil Pressure Sender that I’m going to use together with OLED to show an oil pressure in my car.

However I’m struggling with a code. I’ve copy-pasted a part of the code, responsible for sensor calculations from GitHub - MurdockGT/Classic-Car-Digital-Dash: Full digital monitoring of classic car with coolant fan control with Arduino Mega
I’ve tried combining it together with OLED libraries, the problem is - code is compiling fine, display is initializing, shows Adafruit logo and after that - it’s completely blank. I’ve tried to put data through Serial monitor instead of an oled - same result, Serial shows completely nothing. What’s the issue?

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

//dla SPI:
#define OLED_MOSI   9 //SDA
#define OLED_CLK   10 //SCL
#define OLED_DC    11
#define OLED_CS    12
#define OLED_RESET 13
Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

const byte oilPressPin = A0;
const float aRef = 5.0;

void setup() {
  Serial.begin(9600);
  //display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.begin(SSD1306_SWITCHCAPVCC);
  display.display();
  delay(3000);
  display.clearDisplay();
  delay(3000);
  display.display();
}

void loop() {
  int getOilpressure();
  // using VDO Oil Pressure guage, 10BAR
  float array[12] = {
    // Voltage From Sensor on left // Corresponding Temprature on right  ,
    //You find this by using voltage divider forumla. Current set is for a 330 ohm R1 and R2 is your VDO Oil Pressure sensor

    2.105263 , 0.1,
    1.944444 , 14.5,
    1.764706 , 29,
    1.5625 , 43.5,
    1.071429 , 72.5,
    0.4141189 , 100,
  };
  int val = 0;
  for (int i = 1; i <= 10; i++)
  {
    val += analogRead(oilPressPin);
  }
  val += 5; // allows proper rounding due to using integer math
  val /= 10; // get average value
  float voltage = val / 1023.0 * aRef;

  float oilp;
  if (voltage >= array[0])
  {
    oilp = array[1];
  }
  else if (voltage <= array[10])
  {
    oilp = array[11];
  }
  else
  {
    for (int i = 1; i < 12; i++)
    {
      int ii = 2 * i;
      if (voltage <= array[ii] && voltage >= array[ii + 2])
      {
        oilp = array[ii + 1] + ((array[ii + 3] - array[ii + 1]) * (voltage - array[ii]) / (array[ii + 2] - array[ii]));
        break;
      }
    }
  }
  int oilpres = oilp;
  return oilpres;

  //added a delay, thought it can help - it didn't
  delay(200);
  Serial.print("Pressure: ");
  Serial.print(oilpres);

  /*
   * display.clearDisplay();
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(0,0);
display.println("Pressure:");
display.setTextSize(2);
display.setTextColor(WHITE);
display.setCursor(5,25);
display.println(oilpres);
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(20, 54);
display.println("BAR");
display.setCursor(70, 0);
display.println("Temp:");
display.setTextSize(2);
display.setCursor(65, 25);
display.println("test");
display.setTextSize(1);
display.setCursor(90, 54);
display.println("*C");
display.display();
delay(500);
   */
}

Could it be the "return" before you print or display anything?

Hint: a void function doesn't return anything.

Solved, thank you for pointing that out :slight_smile:

Also i think you were either going to create a function or thought you did.int getOilpressure();And personally i would set the pinMode() for all pins used even if i do set them to INPUT which is default.

Deva_Rishi:
Also i think you were either going to create a function or thought you did.int getOilpressure();And personally i would set the pinMode() for all pins used even if i do set them to INPUT which is default.

Thanks for the advice!

Now,
I want to convert the original code (which is not mine) to show readout as a float. I’ve managed to do that, however, when the pressure is 0 BAR on OLED - it shows it as “inf”, probably it tries to divide by zero somewhere in the code? How to fix that?

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

//dla SPI:
#define OLED_MOSI   9 //SDA
#define OLED_CLK   10 //SCL
#define OLED_DC    11
#define OLED_CS    12
#define OLED_RESET 13
Adafruit_SSD1306 display(OLED_MOSI, OLED_CLK, OLED_DC, OLED_RESET, OLED_CS);

const byte oilPressPin = A0;
const byte oilWarninglight = 7;
const float aRef = 5.0;

void setup() {
  pinMode(A0, INPUT);
  Serial.begin(9600);
  //display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.begin(SSD1306_SWITCHCAPVCC);
  display.display();
  delay(3000);
  display.clearDisplay();
  delay(3000);
  display.display();
}

void loop() {
  
  // using VDO Oil Pressure gauge, 10BAR
  float array[12] = {
    // Voltage From Sensor on left // Corresponding Temperature on right  ,
    //You find this by using voltage divider formula. Current set is for a 330 ohm R1 and R2 is your VDO Oil Pressure sensor

    2.118263 , 0.1,
    1.944444 , 1.0,
    1.764706 , 2.0,
    1.5625 , 3.0,
    1.071429 , 5.0,
    0.4141189 , 6.89,
  };
  int val = 0;
  for (float i = 1; i <= 10; i++)
  {
    val += analogRead(oilPressPin);
  }
  val += 5.0; // allows proper rounding due to using integer math
  val /= 10.0; // get average value
  float voltage = val / 1023.0 * aRef;

  float oilp;
  if (voltage >= array[0])
  {
    oilp = array[1];
  }
  else if (voltage <= array[10])
  {
    oilp = array[11];
  }
  else
  {
    for (float i = 1; i < 12; i++)
    {
      int ii = 2 * i;
      if (voltage <= array[ii] && voltage >= array[ii + 2])
      {
        oilp = array[ii + 1] + ((array[ii + 3] - array[ii + 1]) * (voltage - array[ii]) / (array[ii + 2] - array[ii]));
        break;
      }
    }
  }
  float oilpres = oilp;

display.clearDisplay();
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(5,0);
display.println("Pressure:");
display.setTextSize(2);
display.setTextColor(WHITE);
display.setCursor(10,25);
display.println(oilpres);
display.setTextSize(1);
display.setTextColor(WHITE);
display.setCursor(22, 42);
display.println("BAR");
display.setCursor(70, 0);
display.println("Oil Temp:");
display.setTextSize(2);
display.setCursor(75, 25);
display.println("24");
display.setTextSize(1);
display.setCursor(100, 25);
display.println("*C");
display.setTextSize(1);
display.setCursor(22, 52);
display.println("RIP");
display.setTextSize(1);
display.setCursor(80, 52);
display.println("COLD!");
display.display();
delay(200);

return oilpres;
}

it shows it as “inf”, probably it tries to divide by zero somewhere in the code?

on an ESP that will just crash.
just as a note for (float i = 1; i <= 10; i++) this should not be a float.
also i am wondering if this actually prints the float value ?display.println(oilpres);