CIR - Infrared remote decoder for NEC protocol

[fj604 34]

A quick demo that can be converted to a library:

 

/* Consumer IR receiver demo for the NEC protocol for MSP430G2231 (Launchpad)
* Requires a 38kHz IR detector such as Vishay TSOP4838 on Pin 4 (P1.2/TA0.1)
* Toggles a LED when a particular IR remote button is pushed
* For more details on the NEC protocol, see http://www.sbprojects.com/knowledge/ir/nec.php 
*/ 

#include 

// IR pulse timing constants in microseconds

#define HP_MIN      8500    // Header pulse minimum duration
#define HP_MAX      9500    // Header pulse maximum duration
#define HPL_MIN     4100    // Header pulse low minimum duration
#define HPL_MAX     4800    // Header pulse low maximum duration
#define RPT_MIN     1900    // Repeat pulse minimum duration
#define RPT_MAX     2500    // Repeat pulse minimum duration
#define BP_MIN      450     // Bit pulse minimum duration
#define BP_MAX      650     // Bit pulse maximum duration
#define ONE_MIN     2000    // Logical one minumum duration
#define ONE_MAX     2500    // Logical one maxumum duration
#define ZERO_MIN    1000    // Logical zero minumum duration
#define ZERO_MAX    1300    // Logical zero maxumum duration

#define FALSE 0
#define TRUE (!FALSE)
#define IR_REPEAT 0xFF00    // Special repeat code
#define MAX_DATA_BITS 32    // NEC protocol provides for 32 bits of data

#define PIN_IR      BIT2    // This must be TA0.1
#define PIN_LED1    BIT0    // LED1 on the Launchpad

#define BUTTON_POWER    0x00FD00FF    // This is a code for the button to toggle the LED

static volatile unsigned long data;

void ir_init(void)
{
   _disable_interrupts();
   BCSCTL1 = CALBC1_1MHZ;                  // Set DCO to 1MHz to measure pulses in microseconds
   DCOCTL = CALDCO_1MHZ;
   P1DIR &= ~PIN_IR;                       // Set IR detector pin to input
   P1OUT |= PIN_IR;                        // Set resistor to pull-up
   P1REN |= PIN_IR;                        // Enable resistor
   P1SEL = PIN_IR;                         // set IR detector pin to peripheral function
   TACTL = TASSEL_2 | ID_0 | MC_2;         // SMCLK, Continuous mode, Input divider /1
   TACCTL1 = CM_3 |  CCIS_0 | CAP | CCIE;  // Capture on both edges, Capture Input Select CCI0A, Capture mode, Capture interrupt enable
   _enable_interrupts();
}

void main(void)
{
   WDTCTL = WDTPW | WDTHOLD;       // Stop the Watchdog timer
   P1DIR = PIN_LED1;               // LED1 to output
   ir_init();                      // Initialize IR detection 
   for (;                        // Loop forever
   {
       _low_power_mode_0();        // Wait in LPM0 until the IR remote code is received 
       // Set a breakpoint on the next line and add a watch for the data variable to see the IR code received 
       if (data == BUTTON_POWER)   // If remote power button is pressed
           P1OUT ^= PIN_LED1;      // Toggle LED1 
   }
}
#pragma vector=TIMERA1_VECTOR
__interrupt void timer_A_interrupt(void)
{
   static unsigned char hp, hr;                    //header pulse received, header received
   static unsigned char br;                        // bits received
   static unsigned char pulse=FALSE;               // pulse in progress
   static volatile unsigned char ready = FALSE;    // data ready
   static unsigned int pw=0, bw=0;                 // pulse width, bit width
   unsigned int i = TAIV;                          // Read TAIV to clear CCIFG

   // Is this the beginning or the end of the pulse?
   if (!pulse)
   // start of the pulse
   {
       bw=TACCR1;
       // reset Timer
       TACTL |= TACLR;
       pulse=TRUE;
       // Has the header pulse just been received?
       if (hp)
       {
           // Is the header duration in range?
           if (bw>HPL_MIN && bw            {
               hr=TRUE;
               br=0;
               data=0;
               ready=FALSE;
           }
           // is it a repeat code?
           else if (bw>RPT_MIN && bw            {
               data=IR_REPEAT;
               hr=FALSE;
               ready=TRUE;
           }
       }
       // Was there a bit pulse before, and also has the header been received?
       if(hr && pw>BP_MIN && pw        {
           if (bw>ONE_MIN && bw            {
               data<<=1;
               data++;
               br++;
           }
           else if (bw>ZERO_MIN && bw            {
               data<<=1;
               br++;
           }
           if (br==MAX_DATA_BITS)
           {
               hr=FALSE;
               ready=TRUE;
           }
       }
       hp=FALSE;
   }
   else
   // end of the pulse
   {
       pw=TACCR1;
       pulse=FALSE;
       // Is this a header pulse?
       if (pw>HP_MIN && pw        {
           // set Header Pulse Received flag
           hp=TRUE;
           // Reset timer
           TACTL |= TACLR;
       }
       else
       {
           hp=FALSE;
       }
   }
   if (ready)
   {
       ready = FALSE;
       _low_power_mode_off_on_exit();  // Return from LPM
   }
}

 

(edited - added a pullup resistor setting)

[davidnhutch 0]

This is a great demo and I've found it very useful as I'm learning MSP430 (CCS).

 

Do you have similar code for sending four bytes of data via NEC protocol? This would help out a lot.

 

Best regards,

D

[loetsport 0]

Hi, i tried to use the code for IR control of a MSP430F2274.

 

I used Port 1.1 - so the only changes i made was changing the port number and using timer A0.

My code doesn't work so - mabe i forgot something...?

[Arch_ETS 0]

Led is constantly on for me, no idea why.

[akshayaggarwal 0]

hello sir,

 I have been facing 1 issue with this code. on pressing all the buttons i only get 1 value in the data variable. only the repeat value gets transfered to the data variable. can you help me on this. 

regards,

akshay