altos: Reduce deviation at 2400/9600 baud

There's no reason to use 20.5kHz deviation at 2400 and 9600 baud, and
if we get a better receiver, we'll want to use narrower deviation to
have less bandwidth sucking noise into the radio. The new values are
(nominally) 5.125kHz deviation for 9600 baud and 1.5kHz deviation for
2400 baud.

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

1 files changed, 50 insertions, 27 deletions

diff --git a/src/cc1111/ao_radio.c b/src/cc1111/ao_radio.c
index 8f519958..b9821a42 100644
--- a/src/cc1111/ao_radio.c
+++ b/src/cc1111/ao_radio.c
@@ -60,19 +60,19 @@
  *
  *	M = 1, E = 3, bw = 75kHz
  *
- * 20.5 kHz deviation, 9.6kbps signal
+ * 5.125 kHz deviation, 9.6kbps signal
  *
- *	m = 41 / 9.6, which is < 5.5:
+ *	m = 10.25 / 9.6, which is < 5.5:
  *
- *	bw = 2.6 * 20.5 + 0.55 * 9.6 = 58.58kHz
+ *	bw = 2.6 * 5.125 + 0.55 * 9.6 = 18.6kHz
  *
- *	M = 2, E = 3, bw = 62.5kHz
+ *	M = 2, E = 3, bw = 53.6kHz
  *
- * 20.5kHz deviation, 2.4kbps signal
+ * 1.28125kHz deviation, 2.4kbps signal
  *
- *	m = 41 / 2.4, which is > 5.5:
+ *	m = 2.565 / 2.4, which is < 5.5:
  *
- *	bw = 2.1 * 20.5 + 1.9 * 2.4 = 47.61kHz
+ *	bw = 2.6 * 20.5 + 1.9 * 2.4 = 47.61kHz
  *
  *	M = 3, E = 3, bw = 53.6kHz
  *
@@ -84,7 +84,7 @@
  */
 
 #define CHANBW_M_384	1
-#define CHANBW_M_96	2
+#define CHANBW_M_96	3
 #define CHANBW_M_24	3
 #define CHANBW_E	3
 
@@ -115,11 +115,19 @@
  *
  * F = 24e6/2**17 * (8 + DEVIATION_M) * 2**DEVIATION_E
  *
- * So M is 6 and E is 3
+ * For 20.5kHz deviation, M is 6 and E is 3
+ * For 5.125kHz deviation, M is 6 and E is 1
+ * For 1.28125kHz deviation, M is 0 and E is 0
  */
 
-#define DEVIATION_M	6
-#define DEVIATION_E	3
+#define DEVIATION_M_384	6
+#define DEVIATION_E_384	3
+
+#define DEVIATION_M_96	6
+#define DEVIATION_E_96	1
+
+#define DEVIATION_M_24	0
+#define DEVIATION_E_24	0
 
 /*
  * For our RDF beacon, set the symbol rate to 2kBaud (for a 1kHz tone),
@@ -182,9 +190,6 @@ static __code uint8_t radio_setup[] = {
 
 	RF_CHANNR_OFF,		0,
 
-	RF_DEVIATN_OFF,		((DEVIATION_E << RF_DEVIATN_DEVIATION_E_SHIFT) |
-				 (DEVIATION_M << RF_DEVIATN_DEVIATION_M_SHIFT)),
-
 	/* SmartRF says set LODIV_BUF_CURRENT_TX to 0
 	 * And, we're not using power ramping, so use PA_POWER 0
 	 */
@@ -284,8 +289,10 @@ static __code uint8_t fixed_pkt_setup[] = {
 				 RF_MDMCFG1_NUM_PREAMBLE_4 |
 				 (2 << RF_MDMCFG1_CHANSPC_E_SHIFT)),
 
-	RF_DEVIATN_OFF,		((DEVIATION_E << RF_DEVIATN_DEVIATION_E_SHIFT) |
-				 (DEVIATION_M << RF_DEVIATN_DEVIATION_M_SHIFT)),
+#if !HAS_RADIO_RATE
+	RF_DEVIATN_OFF,		((DEVIATION_E_384 << RF_DEVIATN_DEVIATION_E_SHIFT) |
+				 (DEVIATION_M_384 << RF_DEVIATN_DEVIATION_M_SHIFT)),
+#endif
 
 	/* max packet length -- now set inline */
 	RF_PKTCTRL1_OFF,	((1 << PKTCTRL1_PQT_SHIFT)|
@@ -298,19 +305,34 @@ static __code uint8_t fixed_pkt_setup[] = {
 };
 
 #if HAS_RADIO_RATE
-static __code uint8_t packet_rate_setup[] = {
+static __code struct {
+	uint8_t		mdmcfg4;
+	uint8_t		deviatn;
+} packet_rate_setup[] = {
 	/* 38400 */
-	((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
-	 (CHANBW_M_384 << RF_MDMCFG4_CHANBW_M_SHIFT) |
-	 (DRATE_E_384 << RF_MDMCFG4_DRATE_E_SHIFT)),
+	{
+		((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
+		 (CHANBW_M_384 << RF_MDMCFG4_CHANBW_M_SHIFT) |
+		 (DRATE_E_384 << RF_MDMCFG4_DRATE_E_SHIFT)),
+		((DEVIATION_E_384 << RF_DEVIATN_DEVIATION_E_SHIFT) |
+		 (DEVIATION_M_384 << RF_DEVIATN_DEVIATION_M_SHIFT)),
+	},
 	/* 9600 */
-	((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
-	 (CHANBW_M_96 << RF_MDMCFG4_CHANBW_M_SHIFT) |
-	 (DRATE_E_96 << RF_MDMCFG4_DRATE_E_SHIFT)),
+	{
+		((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
+		 (CHANBW_M_96 << RF_MDMCFG4_CHANBW_M_SHIFT) |
+		 (DRATE_E_96 << RF_MDMCFG4_DRATE_E_SHIFT)),
+		((DEVIATION_E_96 << RF_DEVIATN_DEVIATION_E_SHIFT) |
+		 (DEVIATION_M_96 << RF_DEVIATN_DEVIATION_M_SHIFT)),
+	},
 	/* 2400 */
-	((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
-	 (CHANBW_M_24 << RF_MDMCFG4_CHANBW_M_SHIFT) |
-	 (DRATE_E_24 << RF_MDMCFG4_DRATE_E_SHIFT)),
+	{
+		((CHANBW_E << RF_MDMCFG4_CHANBW_E_SHIFT) |
+		 (CHANBW_M_24 << RF_MDMCFG4_CHANBW_M_SHIFT) |
+		 (DRATE_E_24 << RF_MDMCFG4_DRATE_E_SHIFT)),
+		((DEVIATION_E_24 << RF_DEVIATN_DEVIATION_E_SHIFT) |
+		 (DEVIATION_M_24 << RF_DEVIATN_DEVIATION_M_SHIFT)),
+	},
 };
 #endif
 
@@ -380,7 +402,8 @@ ao_radio_get(uint8_t len)
 	RF_FREQ0 = (uint8_t) (ao_config.radio_setting);
 	RF_PKTLEN = len;
 #if HAS_RADIO_RATE
-	RF_MDMCFG4 = packet_rate_setup[ao_config.radio_rate];
+	RF_MDMCFG4 = packet_rate_setup[ao_config.radio_rate].mdmcfg4;
+	RF_DEVIATN = packet_rate_setup[ao_config.radio_rate].deviatn;
 #endif
 }