[new] XBee auto-baudrate in api mode

conf/firmwares/subsystems/fixedwing/telemetry_xbee_api.makefile

@@ -3,7 +3,7 @@
 # XBee modems in API mode
 
 ap.CFLAGS += -DUSE_$(MODEM_PORT)
-ap.CFLAGS += -D$(MODEM_PORT)_BAUD=$(MODEM_BAUD)
+ap.CFLAGS += -D$(MODEM_PORT)_BAUD=$(MODEM_BAUD) -DXBEE_BAUD=$(MODEM_BAUD)
 
 ap.CFLAGS += -DDOWNLINK -DDOWNLINK_FBW_DEVICE=$(MODEM_PORT) -DDOWNLINK_AP_DEVICE=$(MODEM_PORT) -DXBEE_UART=$(MODEM_PORT)
 ap.CFLAGS += -DDOWNLINK_TRANSPORT=XBeeTransport -DDATALINK=XBEE

conf/firmwares/subsystems/rotorcraft/telemetry_xbee_api.makefile

@@ -7,7 +7,7 @@
 #
 
 ap.CFLAGS += -DUSE_$(MODEM_PORT)
-ap.CFLAGS += -D$(MODEM_PORT)_BAUD=$(MODEM_BAUD)
+ap.CFLAGS += -D$(MODEM_PORT)_BAUD=$(MODEM_BAUD) -DXBEE_BAUD=$(MODEM_BAUD)
 
 ap.CFLAGS += -DDOWNLINK -DDOWNLINK_DEVICE=$(MODEM_PORT) -DXBEE_UART=$(MODEM_PORT)
 ap.CFLAGS += -DDOWNLINK_TRANSPORT=XBeeTransport -DDATALINK=XBEE

sw/airborne/subsystems/datalink/xbee.c

@@ -34,27 +34,92 @@ uint8_t xbee_rssi;
 struct xbee_transport xbee_tp;
 
 #define AT_COMMAND_SEQUENCE "+++"
-#define AT_INIT_PERIOD_US 2000000
 #define AT_SET_MY "ATMY"
 #define AT_AP_MODE "ATAP1\r"
 #define AT_EXIT "ATCN\r"
 
-uint32_t xbee_delay_time;
+static uint8_t xbee_text_reply_is_ok(void)
+{
+  char c[2];
+  int count = 0;
+
+  while (TransportLink(XBEE_UART,ChAvailable()))
+  {
+    char cc = TransportLink(XBEE_UART,Getch());
+    if (count < 2)
+      c[count] = cc;
+    count++;
+  }
+
+  if ((count > 2) && (c[0] == 'O') && (c[1] == 'K'))
+    return TRUE;
+
+  return FALSE;
+}
+
+static uint8_t xbee_try_to_enter_api(void) {
+
+  /** Switching to AT mode (FIXME: busy waiting) */
+  XBeePrintString(XBEE_UART,AT_COMMAND_SEQUENCE);
+
+  /** - busy wait 1.25s */
+  sys_time_usleep(1250000);
+
+  return xbee_text_reply_is_ok();
+}
+
+#define XBeeUartSetBaudrate(_a) TransportLink(XBEE_UART,SetBaudrate(_a))
+
+
+#if XBEE_BAUD == B9600
+    #define XBEE_BAUD_ALTERNATE B57600
+    #define XBEE_ATBD_CODE "ATBD3\rATWR\r"
+    #pragma message "Experimental: XBEE-API@9k6 auto-baudrate 57k6 -> 9k6 (stop ground link for correct operation)"
+#elif XBEE_BAUD == B57600
+    #define XBEE_BAUD_ALTERNATE B9600
+    #define XBEE_ATBD_CODE "ATBD6\rATWR\r"
+    #pragma message "Experimental: XBEE-API@57k6 auto-baudrate 9k6 -> 57k6 (stop ground link for correct operation)"
+#else
+    #warning XBEE-API Non default baudrate: auto-baud disabled
+#endif
 
 
 void xbee_init( void ) {
   xbee_tp.status = XBEE_UNINIT;
   xbee_tp.trans.msg_received = FALSE;
 
+  // Empty buffer before init process
+  while (TransportLink(XBEE_UART,ChAvailable()))
+    TransportLink(XBEE_UART,Getch());
+
 #ifndef NO_XBEE_API_INIT
   /** - busy wait 1.25s */
   sys_time_usleep(1250000);
 
-  /** Switching to AT mode (FIXME: busy waiting) */
-  XBeePrintString(XBEE_UART,AT_COMMAND_SEQUENCE);
+  if (! xbee_try_to_enter_api() )
+  {
+    #ifdef XBEE_BAUD_ALTERNATE
 
-  /** - busy wait 1.25s */
-  sys_time_usleep(1250000);
+      // Badly configured... try the alternate baudrate:
+      XBeeUartSetBaudrate(XBEE_BAUD_ALTERNATE);
+      if ( xbee_try_to_enter_api() )
+      {
+        // The alternate baudrate worked,
+        XBeePrintString(XBEE_UART,XBEE_ATBD_CODE);
+      }
+      else
+      {
+        // Complete failure, none of the 2 baudrates result in any reply
+        // TODO: set LED?
+
+        // Set the default baudrate, just in case everything is right
+        XBeeUartSetBaudrate(XBEE_BAUD);
+        XBeePrintString(XBEE_UART,"\r");
+      }
+
+    #endif
+    // Continue changing settings until the EXIT is issued.
+  }
 
   /** Setting my address */
   XBeePrintString(XBEE_UART,AT_SET_MY);
@@ -70,5 +135,8 @@ void xbee_init( void ) {
 
   /** Switching back to normal mode */
   XBeePrintString(XBEE_UART,AT_EXIT);
+
+  XBeeUartSetBaudrate(XBEE_BAUD);
+
 #endif
 }