altos: Reduce deviation at 2400/9600 baud

[fw/altos] / src / drivers / ao_cc115l.c

diff --git a/src/drivers/ao_cc115l.c b/src/drivers/ao_cc115l.c
index b5103f9bec5edb5692f758062f37ce740eea7cc2..cf61acfe9c4ae45a6def0d88caf05c8d3d0dac96 100644 (file)
--- a/src/drivers/ao_cc115l.c
+++ b/src/drivers/ao_cc115l.c
@@ -249,23 +249,41 @@ ao_radio_idle(void)
 }
 
 /*
- * Packet deviation is 20.5kHz
+ * Packet deviation
  *
  *     fdev = fosc >> 17 * (8 + dev_m) << dev_e
  *
+ * For 38400 baud, use 20.5kHz:
+ *
  *             26e6 / (2 ** 17) * (8 + 5) * (2 ** 3) = 20630Hz
+ *
+ * For 9600 baud, use 5.125kHz:
+ *
+ *             26e6 / (2 ** 17) * (8 + 5) * (2 ** 1) = 5157Hz
+ *
+ * For 2400 baud, use 1.5kHz:
+ *
+ *             26e6 / (2 ** 17) * (8 + 0) * (2 ** 0) = 1587Hz
  */
 
-#define PACKET_DEV_E   3
-#define PACKET_DEV_M   5
+#define PACKET_DEV_E_384       3
+#define PACKET_DEV_M_384       5
+
+#define PACKET_DEV_E_96                1
+#define PACKET_DEV_M_96                5
+
+#define PACKET_DEV_E_24                0
+#define PACKET_DEV_M_24                0
 
 /*
- * For our packet data, set the symbol rate to 38400 Baud
+ * For our packet data:
  *
  *              (256 + DATARATE_M) * 2 ** DATARATE_E
  *     Rdata = -------------------------------------- * fosc
  *                          2 ** 28
  *
+ * For 38400 baud:
+ *
  *             (256 + 131) * (2 ** 10) / (2**28) * 26e6 = 38383
  *
  *     DATARATE_M = 131
@@ -279,20 +297,33 @@ ao_radio_idle(void)
 #define PACKET_DRATE_E_96      8
 #define PACKET_DRATE_E_24      6
 
-static const uint16_t packet_rate_setup[] = {
-       [AO_RADIO_RATE_38400] = ((0xf << 4) |
-                                (PACKET_DRATE_E_384 << CC115L_MDMCFG4_DRATE_E)),
-
-       [AO_RADIO_RATE_9600] = ((0xf << 4) |
-                               (PACKET_DRATE_E_96 << CC115L_MDMCFG4_DRATE_E)),
-
-       [AO_RADIO_RATE_2400] = ((0xf << 4) |
-                               (PACKET_DRATE_E_24 << CC115L_MDMCFG4_DRATE_E)),
+static const struct {
+       uint8_t         mdmcfg4;
+       uint8_t         deviatn;
+} packet_rate_setup[] = {
+       [AO_RADIO_RATE_38400] = {
+               .mdmcfg4 = ((0xf << 4) |
+                           (PACKET_DRATE_E_384 << CC115L_MDMCFG4_DRATE_E)),
+               .deviatn = ((PACKET_DEV_E_384 << CC115L_DEVIATN_DEVIATION_E) |
+                           (PACKET_DEV_M_384 << CC115L_DEVIATN_DEVIATION_M)),
+       },
+
+       [AO_RADIO_RATE_9600] = {
+               .mdmcfg4 = ((0xf << 4) |
+                           (PACKET_DRATE_E_96 << CC115L_MDMCFG4_DRATE_E)),
+               .deviatn = ((PACKET_DEV_E_96 << CC115L_DEVIATN_DEVIATION_E) |
+                           (PACKET_DEV_M_96 << CC115L_DEVIATN_DEVIATION_M)),
+       },
+
+       [AO_RADIO_RATE_2400] = {
+               .mdmcfg4 = ((0xf << 4) |
+                           (PACKET_DRATE_E_24 << CC115L_MDMCFG4_DRATE_E)),
+               .deviatn = ((PACKET_DEV_E_24 << CC115L_DEVIATN_DEVIATION_E) |
+                           (PACKET_DEV_M_24 << CC115L_DEVIATN_DEVIATION_M)),
+       },
 };
 
 static const uint16_t packet_setup[] = {
-       CC115L_DEVIATN,         ((PACKET_DEV_E << CC115L_DEVIATN_DEVIATION_E) |
-                                (PACKET_DEV_M << CC115L_DEVIATN_DEVIATION_M)),
        CC115L_MDMCFG3,         (PACKET_DRATE_M),
        CC115L_MDMCFG2,         (0x00 |
                                 (CC115L_MDMCFG2_MOD_FORMAT_GFSK << CC115L_MDMCFG2_MOD_FORMAT) |
@@ -418,7 +449,8 @@ ao_radio_set_mode(uint16_t new_mode)
 
        changes = new_mode & (~ao_radio_mode);
        if (changes & AO_RADIO_MODE_BITS_PACKET_TX) {
-               ao_radio_reg_write(CC115L_MDMCFG4, packet_rate_setup[ao_config.radio_rate]);
+               ao_radio_reg_write(CC115L_MDMCFG4, packet_rate_setup[ao_config.radio_rate].mdmcfg4);
+               ao_radio_reg_write(CC115L_DEVIATN, packet_rate_setup[ao_config.radio_rate].deviatn);
 
                for (i = 0; i < sizeof (packet_setup) / sizeof (packet_setup[0]); i += 2)
                        ao_radio_reg_write(packet_setup[i], packet_setup[i+1]);