I need help to implement a timer

Community Jobs and Paid Consultancy
1

Hey. I have a project in which I check the posture of a person, with a Accelerometer(MPU6050). When the y value (see void GetAngle ()) is between 110 and 90 degrees, the person has a good posture. Everything outside of it is a bad posture. Now I have designed it so that the tool first checks whether the person has a correct or incorrect posture and then sends a message (see case: CHECK), When the person has a Bad posture (y >= 110 || y <= 70) the program switches to case: COUNTDOWN. Now I want to implement a timer in the case COUNTDOWN, that if the person still has a wrong posture after 2 minutes, then the program switches to the case: MESSAGE. How can I implement this timer? I also want to stop the loop when a 0 comes in via the bluetooth. This does not work yet. Thanks in advance for your help.
Below is the full program.

#include <SoftwareSerial.h>
#include <Wire.h>
#include <math.h>
SoftwareSerial BT(0, 1); // RX, TX-pin
int BluetoothData = 0; // BT init state
const int MPU_addr = 0x68;
int16_t AcX, AcY, AcZ, Tmp, GyX, GyY, GyZ;
int minVal = 265;
int maxVal = 402;
int StartMillis;
bool StartSign = false;
double x;
double y;
double z;
int c;
enum state { CHECK, COUNTDOWN, MESSAGE };
state current_state;
unsigned long countdownMs;

void setup()
{
  Serial.begin(9600);
  Wire.begin();
  Wire.beginTransmission(MPU_addr);
  Wire.write(0x6B);
  Wire.write(0);
  Wire.endTransmission(true);
  current_state = CHECK;
}

void GetAngle()
{
  Wire.beginTransmission(MPU_addr);
  Wire.write(0x3B);
  Wire.endTransmission(false);
  Wire.requestFrom(MPU_addr, 14, true);
  AcX = Wire.read() << 8 | Wire.read();
  AcY = Wire.read() << 8 | Wire.read();
  AcZ = Wire.read() << 8 | Wire.read();
  int xAng = map(AcX, minVal, maxVal, -90, 90);
  int yAng = map(AcY, minVal, maxVal, -90, 90);
  int zAng = map(AcZ, minVal, maxVal, -90, 90);

  x = RAD_TO_DEG * (atan2(-yAng, -zAng) + PI); // Rad to degrees
  y = RAD_TO_DEG * (atan2(-xAng, -zAng) + PI);
  z = RAD_TO_DEG * (atan2(-yAng, -xAng) + PI);
}

void loop()
{
  while (1)
  {
    if (Serial.available())
    {
      c = Serial.read();

      switch (c)
      {
        case ('1'):
          StartSign = true;
          Serial.println("program start");
          break;


        case ('0'):
          StartSign = false;
          Serial.println("program stopped");
          break;
      }

      if (!Serial.available())
      {


        while (StartSign == true)
        {
          GetAngle();
          switch (current_state)
          {
            case CHECK:
              if (y >= 110 || y <= 70)                              // Wrong posture
              {
                countdownMs = millis();
                current_state = COUNTDOWN;
                Serial.println("Bad posture");
              }

              else                                                  // Good posture
              {
                // do nothing;
                Serial.println("Good posture");
              }
              break;

            case COUNTDOWN:
              if ((y >= 110 || y <= 70))                           // Still a wrong posture
              {
                current_state = MESSAGE;
              }
              else                                                 // Good posture
              {
                current_state = CHECK;
              }

              break;

            case MESSAGE:
              if (y >= 110 || y <= 70)
              {
                Serial.println("Bad posture");
              }

              else
              {
                current_state = CHECK;
                Serial.println("Good posture");
              }
              break;
          }
        }
      }
    }
  }
}
2

let's say you have a

unsigned long alarm_time =  0L ; 

void loop() {
  if (bad_posture()) { 
      if(alarm_time == 0) 
         alarm_time = millis() + 120000; //  wake me up after 2 minutes. 
  } else { 
     // we-re back to good posture, set alarm time back to 0 
     alarm_time = 0; 
  } 
  // now just check if alarm_time is expired
  if (alarm_time < millis() && alarm_time > 0) ring_the_alarm(); 

}

You write your own ring_the_alarm() and boolean bad_posture()

3

I would recommend that you use millis(). It would be something like

//2 minutes = 120 seconds = 120000 ms

unsigned long interval = 120000;
 
unsigned long time_now = 0;

void loop()
{
   //where you want the timer  
   
if(incorrect_posture )
{
//start the timer
   Serial.println("warning 1");
   time_now = millis();
   //now check if it exceeds interval
    if(millis() >time_now + interval){
           Serial.println("warning 2");


    }
else//reset timer posture has been corrected
{
time_now = millis();
}
else{
//other code
}

This is not supposed to be a solution, just a pointer in the right direction. Incase you need/want to consult, feel free to PM me

4

A much simpler form:

unsigned long alarm_time = millis() + 120000;

void loop() {
    // while posture is good postpone the alarm with two minutes.
    if (good_posture()) alarm_time = millis() + 120*1000; 

    if (alarm_time < millis()) ring_the_alarm();
}
5

When i grow up i wanna write answers like this (:

blimpyway:
let's say you have a

unsigned long alarm_time =  0L ;

void loop() {
 if (bad_posture()) {
     if(alarm_time == 0)
        alarm_time = millis() + 120000; //  wake me up after 2 minutes.
 } else {
    // we-re back to good posture, set alarm time back to 0
    alarm_time = 0;
 }
 // now just check if alarm_time is expired
 if (alarm_time < millis() && alarm_time > 0) ring_the_alarm();

}




You write your own ring_the_alarm() and boolean bad_posture()
6

Thanks Blimpyway your solution worked!

7