NEC Encoder in C

NEC_Encode.c

// By: NotPike
// NEC Encoding  

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>


// Varibals
#define LEN 16 //Bytes

// Commands
const uint8_t commands[32] = {
	0x32, 	// Pause
	0x78, 	// On/Off
	0x70, 	// P1
	0x60, 	// P2
	0xCA, 	// P3 SKIP
	0x20, 	// F1
	0xF2, 	// Up
	0xA0, 	// F2
	0x84, 	// Left
	0x44, 	// OK
	0xC4, 	// Right
	0x30, 	// F3
	0x80, 	// Down
	0xB0, 	// F4
	0xF0, 	// 1
	0x08, 	// 2
	0x88, 	// 3
	0x48, 	// 4
	0xC8, 	// 5
	0x28, 	// 6
	0xA8, 	// 7
	0x68, 	// 8
	0xE8, 	// 9
	0x18, 	// Music_Karaoke
	0x98, 	// 0
	0x58, 	// Lock_Queue
	0xD0, 	// Zone 1 Vol+
	0x90, 	// Zone 2 Vol+
	0xC0, 	// Zone 3 Vol+
	0x50, 	// Zone 1 Vol-
	0x10, 	// Zone 2 Vol-
	0x40, 	// Zone 3 Vol-
};


// Function Refered From Furrtek's Havoc Port
// https://github.com/furrtek/portapack-havoc/blob/master/firmware/application/apps/ui_touchtunes.cpp#L75
void encode(char *out, uint8_t command, int pin) {

	// Variables
	size_t bit;                                      // Bit counter
	uint64_t decodeMsg = 0x5D;                       // Sync Word + decoded value
	uint8_t encodeMsg;			    	 // Bit holder before encoded values are moved to *out		      
	
	// Preamble 0xFFFF00
	out[0] = 0xFF;
	out[1] = 0xFF; 	
	out[2] = 0x00;

	// PIN, LSB First
	for (bit = 0; bit < 8; bit++) {
		decodeMsg <<= 1; 			 // Shift left 1 bit
		if(pin & (1 << bit)) { 			 // If both bits line up add 1
			decodeMsg |= 1;
		}
	}

	// Command and it's complement
	decodeMsg <<= 16;                                // Shift left 16 bits
	decodeMsg |= (command << 8); 			 // Add command shift left 8 bits
	decodeMsg |= (command ^ 0xff); 		         // Add command's complement

	// NEC Encode
	size_t bitSize = 0;                              // Size counter for encodeMsg
	int arrayPos = 3; 				 // Pointer counter for *out
	for(bit = 0; bit < (8 + 8 + 16); bit++) {        // Sync + Pin + Command == 32bit
		if(decodeMsg & 0x80000000UL) {           // If 1
			if(bitSize <= 4) {		
				encodeMsg <<= 4;
				encodeMsg |= 0x8; 	     // 1000 
				decodeMsg <<= 1;
				bitSize += 4;
			} else if(bitSize == 6)	{            // Split the Byte
				encodeMsg <<= 2;
				encodeMsg |= 0x2;
				out[arrayPos] = encodeMsg;   // Add Byte to char array
				arrayPos++;
				encodeMsg <<= 8;             // Wipe the stack 
				decodeMsg <<= 1;
				bitSize = 2;
			} else if(bitSize == 8) {
				out[arrayPos] = encodeMsg;   // Add Byte to char array
				arrayPos++;
				encodeMsg <<= 8;             // Wipe the stack 
				encodeMsg |= 0x8; 	     // 1000 
				decodeMsg <<= 1;
				bitSize = 4;
			}
		} else { 	                             // Else 0
			if(bitSize <=6) {
				encodeMsg <<= 2;
				encodeMsg |= 0x2; 	     // 10
				decodeMsg <<= 1;
				bitSize += 2;
			} else if(bitSize == 8) {
				out[arrayPos] = encodeMsg;   // Add Byte to char array
				arrayPos++;
				encodeMsg <<= 8;             // Wipe the stack 
				encodeMsg |= 0x2; 	     // 10
				decodeMsg <<= 1;
				bitSize = 2;
			}
		}		
	}

	// Add Tail
	if(bitSize == 2) {
		encodeMsg <<= 4;
		encodeMsg |= 0x8; 	    // 1000
		encodeMsg <<= 2; 
	} else if(bitSize == 4)	{
		encodeMsg <<= 4;
		encodeMsg |= 0x8; 	    // 1000 
	} else if(bitSize == 6)	{           // Split the Byte
		encodeMsg <<= 2;
		encodeMsg |= 0x2;           // 10
		out[arrayPos] = encodeMsg;  // Add Byte to char array
		arrayPos++;
		encodeMsg <<= 8;            // Wipe the stack 
	} else if(bitSize == 8) {
		out[arrayPos] = encodeMsg;  // Add Byte to char array
		arrayPos++;
		encodeMsg <<= 8;            // Wipe the stack 
	}
	
	// Pad with 0x00 if msg length is not 16 Bytes
	if(arrayPos == 14) {
		out[14] = encodeMsg;
		out[15] = 0x00;
		out[16] = '\0';
	} else {
		out[15] = 0x00;
		out[16] = '\0';
	} 				
}

// Known values for PIN 000
static const char * const button_array[] = {
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa2\x2a\x28\xaa\x22\x8a\x20\x00",// Skip
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xaa\x22\xa2\x88\xa8\x8a\x20\x00",// Pause
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa2\xaa\xaa\x22\x22\x22\x20\x00",// Down Arrow
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa8\xa2\x2a\x8a\x2a\x22\x20\x00",// Lock Queue
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa2\xaa\x2a\x88\x88\xa2\x20\x00",// Left Arrow
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa8\xaa\x2a\x28\x88\xa2\x20\x00",// OK
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa2\x2a\x8a\xa8\x88\xa2\x20\x00",// Right Arrow
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa8\x88\x8a\xa2\xaa\x22\x20\x00",// Power
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa2\x22\x2a\x2a\xa8\x8a\x20\x00",// Up Arrow
    "\xff\xff\x00\xa2\x88\x8a\x2a\xaa\xa8\x8a\xaa\x2a\x22\x22\x20\x00" // Edit Queue
};

void main() {
	
	// Variables
	static char *list[32];
	unsigned char returnValue[17];

	uint8_t msg[16] = {0xFF, 0xFF, 0x00, 0xa2, 0x88, 0x8a, 0x2a, 0xaa, // Skip
		           0xa2, 0x2a, 0x28, 0xaa, 0x22, 0x8a, 0x20, 0x00};

	uint8_t msg2[16] = {0xFF, 0xFF, 0x00, 0xa2, 0x88, 0x8a, 0x2a, 0xaa, // Edit Queue
			   0xa8, 0x8a, 0xaa, 0x2a, 0x22, 0x22, 0x20, 0x00};


	// TEST 1
	printf("===Test 1 Skip for PIN 000===\n");
	encode(returnValue, commands[4], 0);

	// Step each char and cmp to msg
	int ji;
	for(ji =0; ji < 16; ji++) {
		if(msg[ji] == returnValue[ji]) {
			printf("char %i pass\n",ji);
		} else {
			printf("char %i fail\n",ji);
		} 
	}


	// TEST 2
	printf("\n===Test 2 Edit Que for PIN 000===\n");
	encode(returnValue, commands[3], 0);

	// Step each char and cmp to msg2
	for(ji =0; ji < 16; ji++) {
		if(msg2[ji] == returnValue[ji]) {
			printf("char %i pass\n",ji);
		} else {
			printf("char %i fail\n",ji);
		} 
	}

	// TEST 3
	// Encode all 32 Commands and 256 PINs
	printf("\n==Test 3 Encode All 32 Commands and 256 PINs==\n"); 
	int xx;
	for(xx=0; xx < 255; xx++) {
		int j;
		for(j = 0; j < 32; j +=1) {
			encode(returnValue, commands[j], xx);
			//printf("Command:%i PIN:%i pass\n", j,xx);
		}
	}
	printf("Complete\n"); 
}