File content as of revision 0:94b5c70f818b:

#include "mbed.h"
#include "MODSERIAL.h"

PwmOut pwmpin(D5);
DigitalOut directionpin(D4); 
AnalogIn Pot_meter(A0);
DigitalIn But2(D7);

MODSERIAL pc(USBTX, USBRX);

Ticker Ticker_direction;
Ticker Ticker_But;
//InterruptIn IntBut(D7);

float x=0;

void Potread()
    {
        x = Pot_meter.read();
        pc.printf("%d\n\r",x);
    }

void Direction()
    {
        float u = -0.3f; //determine useful value, -0.3f is just an example 
        directionpin = u > 0.0f; //either true or false 
        pwmpin = fabs(u); //pwm duty cycle can only be positive, floating point absolute value
        pc.printf("Test\r\n");
    }

int main()
{
    pc.baud(115200);
    Ticker_direction.attach(Direction, 0.001);
    Ticker_But.attach(Potread,1);
    //IntBut.fall(Potread);
    
    pwmpin.period_us(60); //60 microseconds PWM period, 16.7 kHz
    while (true) 
    {
    }
}