Random Message code isn't so random

Projects Programming
1

Hello all, I've created a random message generator that should be displaying a random order of preselected phrases after a button press. It is not doing that, the LCD screen i'm using often glitches out and is filled with special characters or cut off phrases. Let me know if there's any other information I can provide.

#include <LCD-I2C.h>
LCD_I2C lcd(0x27, 16, 2);

const char *messages[] = {
  "msg 1",
  "msdg 2",
  "msg 3",
};


#include <Wire.h>
#include <SPI.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_BME280.h>


#define BME_SCK 7
#define BME_MISO 6
#define BME_MOSI 5
#define BME_CS 4

#define SEALEVELPRESSURE_HPA (1015)

Adafruit_BME280 bme(BME_CS, BME_MOSI, BME_MISO, BME_SCK);
unsigned long delayTime;


const int numMessages = sizeof(messages);
const int buttonPin = 2;
const int bu2onPin = 3;
int hits = 0;
int buttonState = 0;
int bu2onState = 0;
int lastButtonState = 0;
int lastBu2onState = 0;
int currentMessageIndex = 0;


void setup() {
  Serial.begin(9600);
  lcd.begin();
  lcd.display();
  lcd.backlight();
  pinMode(buttonPin, INPUT);
  pinMode(bu2onPin, INPUT);
  bool status;

  status = bme.begin();
  if (!status) {
    lcd.setCursor(0, 0);
    lcd.print("sensor error :[");
    delay(2000);
    lcd.clear();
    while (1)
      ;
  }
  lcd.print("sensor online :]");
  delay(1000);
  lcd.clear();
}

void loop() {

  delay(delayTime);
  buttonState = digitalRead(buttonPin);
  bu2onState = digitalRead(bu2onPin);

  if (buttonState != lastButtonState) {
    if (buttonState == HIGH) {
      currentMessageIndex = random(numMessages);
      lcd.clear();
      lcd.setCursor(0, 0);
      lcd.print(messages[currentMessageIndex]);
    }

    delay(500);
  }
  lastButtonState = buttonState;

  if (bu2onState != lastBu2onState) {
    if (bu2onState == LOW) {
      hits++;
      if (hits >= 5) {
        lcd.clear();
        hits = 0;
      }
    }
    lastBu2onState = bu2onState;



    switch (hits) {

      case 1:
        lcd.setCursor(0, 0);
        lcd.print("Temp: ");
        lcd.print(bme.readTemperature());
        lcd.write(223);
        lcd.print("C");
        break;
      case 2:
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Pressure:");
        lcd.print(bme.readPressure() / 100.0F);
        lcd.print("hPa");
        break;
      case 3:
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Altitude: ");
        lcd.print(bme.readAltitude(SEALEVELPRESSURE_HPA));
        lcd.print("m");
        break;
      case 4:
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Humidity: ");
        lcd.print(bme.readHumidity());
        lcd.print("%");
        break;
      case 5:
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Sophie is: ");
        lcd.print(" sexy");
        break;

        delay(500);
    }
  }
}
2

Where does the random part come in? I didn't see it but my eyesight is failing.

3

Hint: print out the value of "numMessages" at program startup. You might be surprised.

const int numMessages = sizeof(messages);

4

I hope I'm not mistaken, but I think it's on line 70:
currentMessageIndex = random(numMessages);

5

I think the right thing would be

const int numMessages = sizeof(messages)/sizeof(messages[0]);
6

Thanks!

I see one problem, the random seed is not being set.

When a button is pressed and released, timing micros() between press and release and taking the low 16 bits is a good way to generate a seed value.

7

Check grounding of power supply, LCD and Arduino.

8

This fixed the problem initially, but it only changed the "random" order the msgs followed eventually it falls into the same pattern. could it be an issue with turning the arduino on and off and expecting diff results?

9

You need to reseed, like every time use the button event.
The generator is pseudo-random.