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Knight Rider w/o wait

Topic last updated 05 Dec 2011, by Wim Huiskamp. 6 replies
Don DeGregori
22 Nov 2011

Many Knight Riders code out there. I'm trying to implement one using Timers and Interrupts instead of the wait function. This way, can run it within a program and not slow program down. Not sure which timer function would work easiest. donde

Igor Martinovski
23 Nov 2011

Do both. Then you'll know which is more appropriate :)

Mark x
24 Nov 2011

This one worked well for me.... Although there might be a cleaner way to do it..... =)

#include "mbed.h"

BusOut scanner(p21, p22, p23, p24, p25, p26, p27, p28);
int activeLed = 0;
int scanDir = 1;
float scanDelay = 0.05;

Ticker scanTimer;

void scanTime() {
    if (scanDir == 1) {
        activeLed ++;
        scanner = 0 << activeLed - 1;
        scanner = 1 << activeLed;
        if (activeLed == 7) {
            scanDir = 0;
        }
    } else {
        activeLed --;
        scanner = 0 << activeLed + 1;
        scanner = 1 << activeLed;
        if (activeLed == 0) {
            scanDir = 1;
        }
    }
}

int main() {
    scanTimer.attach(&scanTime, scanDelay);
    while(1){
//     do stuff
    }
}

Now, having said all of that... If you want to use less pins..... I'd suggest something like this http://www.sparkfun.com/products/9056 ....... or even better, something like this.... http://www.sparkfun.com/products/10136

Good luck!

Don DeGregori
03 Dec 2011
Don DeGregori
03 Dec 2011

Looks like I need to learn how to present code.

Don DeGregori
04 Dec 2011

Forgot about "<<code>>" Thanks Mark x,for good looking version of a Knight Rider. I'll try it out next. Follows is my version, probably the longest on record! donde

// Knight Rider using modulo and 2 Timers
// t1 is for "on" time of LEDS, t2 is for "off" time. To speed the train up, half all values of the modulo.


#include "mbed.h"
#include "m3pi.h"
 
m3pi m3pi;

DigitalOut red1(p13);
DigitalOut red2(p14);
DigitalOut red3(p15);
DigitalOut red4(p16);
DigitalOut red5(p17);
DigitalOut red6(p18);
DigitalOut red7(p19);
DigitalOut red8(p20);
 
Timer t1;
Timer t2;

int main() {
  t1.start();
  t2.start();
     while(1) { 
         if (t1.read_ms() % 3200 == 200)
         red1 = 1;
         if (t1.read_ms() % 3200 == 400)
         red2 = 1;
         if (t2.read_ms() % 800 == 50)
         red1 = 0;
         if (t1.read_ms() % 3200 == 600)
         red3 = 1;
         if (t2.read_ms() % 800 == 100)
         red2 = 0;
         if (t1.read_ms() % 3200 == 800)
         red4 = 1;
         if (t2.read_ms() % 800 == 150)
         red3 = 0;
         if (t1.read_ms() % 3200 == 1000)
         red5 = 1;
         if (t2.read_ms() % 800 == 200)
         red4 = 0;
         if (t1.read_ms() % 3200 == 1200)
         red6 = 1;
         if (t2.read_ms() % 800 == 250)
         red5 = 0;
         if (t1.read_ms() % 3200 == 1400)
         red7 = 1;
         if (t2.read_ms() % 800 == 300)
         red6 = 0;
         if (t2.read_ms() % 3200 == 1600)
         red8 = 1;   
          if (t2.read_ms() % 800 == 350)
         red7 = 0;
         if (t1.read_ms() % 3200 == 1600)
         red7 = 1;
         if (t2.read_ms() % 800 == 400)
         red8 = 0;
         if (t1.read_ms() % 3200 == 2000)
         red6 = 1;
         if (t2.read_ms() % 800 == 450)
         red7 = 0;
         if (t1.read_ms() % 3200 == 2200)
         red5 = 1;
         if (t2.read_ms() % 800 == 500)
         red6 = 0;
         if (t1.read_ms() % 3200 == 2400)
         red4 = 1;
         if (t2.read_ms() % 800 == 550)
         red5 = 0;
         if (t1.read_ms() % 3200 == 2600)
         red3 = 1;
         if (t2.read_ms() % 800 == 600)
         red4 = 0;
         if (t1.read_ms() % 3200 == 2800)
         red2 = 1;   
         if (t2.read_ms() % 800 == 650)
         red3 = 0;
         if (t1.read_ms() % 3200 == 3000)
         red1 = 1;
         if (t2.read_ms() % 800 == 700)
         red2 = 0;
         if (t2.read_ms() % 800 == 750)
         red1 = 0;
         }
}
Wim Huiskamp
05 Dec 2011

Hi Don,

I played around with a simple KITT scanner to test PWM output. You can find it at: http://mbed.org/users/wim/programs/mbed_kitt/m14hz7

It uses a ticker to call a statemachine that updates the LEDs at each call. I use pulsewidth modulated outputs to show a trailing tail of the scanning LED. You can expand this to more LEDs by using all PWM outputs on mbed.

Code looks like something this:

// Variables for Heartbeat and Status
Ticker heartbeat;
bool heartbeatflag=false;

PwmOut K1(LED1);
PwmOut K2(LED2);
PwmOut K3(LED3);
PwmOut K4(LED4);

// Heartbeat monitor
void pulse() {
  static int kitt_state=0;
  
    switch (kitt_state) {
      case 0: 
               //  1000
               K1.pulsewidth(KITT_MAX); // K1 On
               K2.pulsewidth(KITT_20);  // K2 Decay
               K3.pulsewidth(KITT_OFF); // K3 Off
               K4.pulsewidth(KITT_OFF); // K4 Off         
               
               kitt_state++;
               break;
      case 1:
               //  0100     
               K1.pulsewidth(KITT_50);  // K1 Decay
               K2.pulsewidth(KITT_MAX); // K2 On
               K3.pulsewidth(KITT_OFF); // K3 Off
               K4.pulsewidth(KITT_OFF); // K4 Off         
                           
               kitt_state++;
               break;            

//snip code

      case 7:             
               //  1000             
               K1.pulsewidth(KITT_MAX); // K1 On
               K2.pulsewidth(KITT_50);  // K2 Decay
               K3.pulsewidth(KITT_20);  // K3 Decay
               K4.pulsewidth(KITT_OFF); // K4 Off         
                           
               kitt_state = 0;
               break;            

    } //switch
                                         
}


void heartbeat_start() {
  heartbeat.attach(&pulse, 0.1);
  
  K1.period(KITT_PERIOD);          // KITT LEDs period

  heartbeatflag = true;
}

void heartbeat_stop() {
  heartbeat.detach();
  heartbeatflag = false;
}


int main() {

  bool running=true;
  char command;
    pc.printf("Hello World!\n\r");

    heartbeat_start();
             
    while(running) {};
}