altos: Clean up radio CRC handling

Make the FEC code just set the CRC_OK bit like the cc1111 radio does;
eliminates a bunch of weird conventions across the FEC API.

Signed-off-by: Keith Packard <keithp@keithp.com>

6 files changed, 36 insertions, 31 deletions

diff --git a/src/core/ao.h b/src/core/ao.h
index 62eb488e..861a0fd4 100644
--- a/src/core/ao.h
+++ b/src/core/ao.h
@@ -511,6 +511,13 @@ extern __xdata uint8_t ao_radio_dma_done;
 extern __xdata uint8_t ao_radio_done;
 extern __xdata uint8_t ao_radio_mutex;
 
+#ifdef PKT_APPEND_STATUS_1_CRC_OK
+#define AO_RADIO_STATUS_CRC_OK	PKT_APPEND_STATUS_1_CRC_OK
+#else
+#include <ao_fec.h>
+#define AO_RADIO_STATUS_CRC_OK	AO_FEC_DECODE_CRC_OK
+#endif
+
 void
 ao_radio_general_isr(void) ao_arch_interrupt(16);
 
diff --git a/src/core/ao_fec.h b/src/core/ao_fec.h
index f1192b62..771732bd 100644
--- a/src/core/ao_fec.h
+++ b/src/core/ao_fec.h
@@ -70,6 +70,8 @@ ao_fec_encode(const uint8_t *in, uint8_t len, uint8_t *out);
 
 #define AO_FEC_DECODE_BLOCK	(32)	/* callback must return multiples of this many bits */
 
+#define AO_FEC_DECODE_CRC_OK	0x80	/* stored in out[out_len-1] */
+
 uint8_t
 ao_fec_decode(const uint8_t *in, uint16_t in_len, uint8_t *out, uint8_t out_len, uint16_t (*callback)());
 
diff --git a/src/core/ao_fec_rx.c b/src/core/ao_fec_rx.c
index 0d400bb0..d4c98475 100644
--- a/src/core/ao_fec_rx.c
+++ b/src/core/ao_fec_rx.c
@@ -211,6 +211,7 @@ ao_fec_decode(const uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len, ui
 			int8_t		dist = b - (o + 8);	/* distance to last ready-for-writing bit */
 			uint32_t	min_cost;		/* lowest cost */
 			uint8_t		min_state;		/* lowest cost state */
+			uint8_t		byte;
 
 			/* Find the best fit at the current point
 			 * of the decode.
@@ -238,24 +239,27 @@ ao_fec_decode(const uint8_t *in, uint16_t len, uint8_t *out, uint8_t out_len, ui
 			printf ("\tbit %3d min_cost %5d old bit %3d old_state %x bits %02x whiten %0x\n",
 				i/2, min_cost, o + 8, min_state, (bits[p][min_state] >> dist) & 0xff, *whiten);
 #endif
-			if (out_len) {
-				uint8_t	byte = (bits[p][min_state] >> dist) ^ *whiten++;
+			byte = (bits[p][min_state] >> dist) ^ *whiten++;
+			*out++ = byte;
+			if (out_len > 2)
+				crc = ao_fec_crc_byte(byte, crc);
 
-				if (out_len > 2) {
-					crc = ao_fec_crc_byte(byte, crc);
-					*out++ = byte;
-				} else {
-					*out++ = byte ^ (crc >> 8);
-					crc <<= 8;
-				}
-				--out_len;
+			if (!--out_len) {
+				if ((out[-2] == (uint8_t) (crc >> 8)) &&
+				    out[-1] == (uint8_t) crc)
+					out[-1] = AO_FEC_DECODE_CRC_OK;
+				else
+					out[-1] = 0;
+				out[-2] = 0;
+				goto done;
 			}
 			o += 8;
 		}
 	}
+done:
 #if AO_PROFILE
 	ao_fec_decode_start = start_tick;
 	ao_fec_decode_end = ao_profile_tick();
 #endif
-	return len/16;
+	return 1;
 }
diff --git a/src/drivers/ao_cc1120.c b/src/drivers/ao_cc1120.c
index c974613e..30663042 100644
--- a/src/drivers/ao_cc1120.c
+++ b/src/drivers/ao_cc1120.c
@@ -690,12 +690,7 @@ ao_radio_recv(__xdata void *d, uint8_t size)
 
 	ao_radio_put();
 
-	/* Construct final packet */
-
-	if (ret && ((uint8_t *) d)[size] == 0 && ((uint8_t *)d)[size+1] == 0)
-		((uint8_t *) d)[size + 1] = 0x80;
-	else
-		((uint8_t *) d)[size + 1] = 0x00;
+	/* Store the received RSSI value; the crc-OK byte is already done */
 
 	((uint8_t *) d)[size] = (uint8_t) rssi;
 
diff --git a/src/drivers/ao_packet.c b/src/drivers/ao_packet.c
index 19fe0558..28a0c415 100644
--- a/src/drivers/ao_packet.c
+++ b/src/drivers/ao_packet.c
@@ -65,10 +65,8 @@ ao_packet_recv(void)
 	/* Check to see if we got a valid packet */
 	if (!dma_done)
 		return 0;
-#ifdef PKT_APPEND_STATUS_1_CRC_OK
-	if (!(ao_rx_packet.status & PKT_APPEND_STATUS_1_CRC_OK))
+	if (!(ao_rx_packet.status & AO_RADIO_STATUS_CRC_OK))
 		return 0;
-#endif
 
 	/* Accept packets with matching call signs, or any packet if
 	 * our callsign hasn't been configured
diff --git a/src/test/ao_fec_test.c b/src/test/ao_fec_test.c
index 8ce532c8..671fcafc 100644
--- a/src/test/ao_fec_test.c
+++ b/src/test/ao_fec_test.c
@@ -268,18 +268,17 @@ int
 ao_real_packet(void)
 {
 	uint8_t	decode[64];
-	uint8_t	decode_len;
-	int ok = 0;
+	int	ok;
 
-	decode_len = ao_fec_decode(real_packet, 576, decode, 34, NULL);
+	ok = ao_fec_decode(real_packet, 576, decode, 34, NULL);
 
-	if (decode[32] == 0 && decode[33] == 0) {
+	if (ok && decode[33] == AO_FEC_DECODE_CRC_OK) {
 		printf ("match\n");
 
-		ao_fec_dump_bytes(decode, decode_len, "Decode");
-		ok = 1;
+		ao_fec_dump_bytes(decode, 34, "Decode");
 	} else {
 		printf ("actual packet crc error\n");
+		ok = 0;
 	}
 	return ok;
 }
@@ -302,7 +301,7 @@ main(int argc, char **argv)
 	int		receive_len, receive_errors;
 
 	uint8_t		decode[DECODE_LEN(sizeof(original))];
-	int		decode_len;
+	int		decode_ok;
 
 	int		errors = 0;
 	int		error;
@@ -327,17 +326,17 @@ main(int argc, char **argv)
 		receive_len = transmit_len;
 		
 		/* Decode it */
-		decode_len = ao_fec_decode(receive, receive_len, decode, original_len + 2, NULL);
+		decode_ok = ao_fec_decode(receive, receive_len, decode, original_len + 2, NULL);
 
 		/* Check to see if we received the right data */
 		error = 0;
 
-		if (decode_len < original_len + 2) {
-			printf ("len mis-match\n");
+		if (!decode_ok) {
+			printf ("decode failed\n");
 			error++;
 		}
 
-		if (decode[original_len] != 0 || decode[original_len+1] != 0) {
+		if (decode[original_len +1] != AO_FEC_DECODE_CRC_OK) {
 			printf ("crc mis-match\n");
 			error++;
 		}