Actually now that I think about it why do that? Pololu QTRA does not a library as is a very easy sensor. My opinion is :

Connect the output from the sensor to an oscilloscope or voltmeter, Record the output voltage for Black and the output voltage for White. Then use the Analogin or Digitalin, depenting on your sensor, library And then with a simple A-D or D-A converter and some if statements you can read the voltage on the pin.

There are several other ways to do it, see interrupts and negative/positive edge triggered interrups, but this is the easier way.

eg.

Analogin sensorin (p16);

. . .

Vin=sensorin.read()*3.3; Converter if (Vin<2) { counter++; } if (Vin>2) { counter; }

In the example above I used a threshold voltage of 2V. If output voltage for black is 3V and for white is 0.3V, you can use 1.5V threshold.

I hope this helps!!

Sorry, I keep on forgetting thinks I want to say! Be careful though with this easy solution because the program will read the voltage every fraction of a second. So you will need to limit the reading of voltage to 1 time per edge. A bit of challenge for you there. Think of using a state variable for limiting it.

Best regards.

Thanks :) i will try to write something for the QTRA sensor array based on this

No, i did not test it, because i dont have a qtra sensor right now. What is the problem with the code?

it does not work properly. it does not differentiate black from white as it should.

Ok, please give some time to try to help you making a code for my own.

Greetings

Okay. Thanks :)

hi, try this code, i am assuming this QTRA sensor:

• QTR-8RC Reflectance Sensor Array http://www.pololu.com/catalog/product/961

#include "mbed.h"

#define WHITE 1
#define BLACK 0

DigitalInOut sensors[]={(p5),(p6),(p7),(p8),(p9),(p10),(p11),(p12)};  
InterruptIn sensorsEvent[]={(p5),(p6),(p7),(p8),(p9),(p10),(p11),(p12)};
Timer timer;
//p5 = sensor1
//p6 = sensor2
//p7 = sensor3
//p8 = sensor4
//p9 = sensor5
//p10 = sensor6
//p11 = sensor7
//p12 = sensor8
//1 ms=0.001
//1 us=0.000001

const int sensorsSize=8;
int sensorTimeus;

void lowPulseDetected() {
    timer.stop();
    sensorTimeus=timer.read_us();
    timer.reset();
}

int main() {
    int lineColor;    
    
    for(int i=0;i<sensorsSize;i++) {
        sensors[i].output();
        sensors[i]=0;        
    }
    
    sensorsEvent[0].fall(&lowPulseDetected);
    
       //try to read from sensor 1
    sensors[0].output();  //setting as DigitalOutput
    sensors[0]=1;        //high pulse
    wait_us(10);         //delay according to manual        
    sensors[0].input();        
    timer.start();  
    
    if(sensorTimeus<=780) {
        lineColor=WHITE;
    }                      
 
    if(sensorTimeus>780 && sensorTimeus <=10000) {
        lineColor=BLACK;
    }
}

I cant probe the code for my own because i dont have this sensors

Please try and tell me if it works