Basic receiver and bch error checking for TI ChipCon sub-Ghz receivers.

bch.c

#include <cc1110.h>
#include "cc1110-ext.h"
#include <stdint.h>

#define GENPOLY 0x6F63

//! Receives a packet out of the radio from 0xFE00.
char __xdata __at 0xFE00 packet[0xFF];


uint16_t bch() {
	uint8_t byteIdx, bitIdx;
	uint16_t checksum = 0;

	for (byteIdx = 0; byteIdx < PKTLEN; byteIdx++) {
		checksum ^= (uint16_t)packet[byteIdx] << 8;
		for (bitIdx = 0; bitIdx < 8; bitIdx++) {
			if (checksum & 0x8000) {
				checksum = (checksum << 1) ^ GENPOLY;
			} else {
				checksum <<= 1;
			}
		}
	}

	return checksum;
}

void main() {
	unsigned char idx = 0;

	// Disable interrupts.
	RFTXRXIE = 0;

	do {
		// Strobe RX and wait for ready.
		RFST = RFST_SRX;
		while(MARCSTATE != MARC_STATE_RX);

		for(idx = 0; idx < PKTLEN; idx++) {
			// Wait for byte to be ready.
			while(!RFTXRXIF);

			// Clear the flag.
			RFTXRXIF=0;

			// Grab the next byte.
			packet[idx]=RFD;
		}

		// We sync on 16+1 bits, discard last bit.
		packet[PKTLEN-1] &= 0xFE;
	} while (bch());

	P1_4 = 1;
	P1_4 = 0;

	//End receive.
	RFST = RFST_SIDLE;
	while(MARCSTATE != MARC_STATE_IDLE);

	HALT;
}