bacnet-stack/ports/atmega168/rs485.c

@@ -31,7 +31,7 @@
 #include <stdbool.h>
 #include <stdlib.h>
 #include <stdio.h>
-#include "mstp.h"
+//#include "mstp.h"
 
 /* This file has been customized for use with ATMEGA168 */
 #include "hardware.h"
@@ -42,7 +42,19 @@ static uint8_t LED1_Off_Timer;
 static uint8_t LED3_Off_Timer;
 
 /* baud rate */
-static uint32_t RS485_Baud = 38400;
+static uint32_t RS485_Baud = 9600;
+/* autobaud - switch baud on errors if autobaud is true */
+static bool RS485_Autobaud = true;
+/* we saw some data, so we are on an active wire */
+static uint8_t RS485_Data_Count;
+/* count of errors before autobaud switching */
+static uint8_t RS485_Error_Count;
+/* time limit */
+#define RS485_ERROR_TIMEOUT 1000
+/* millisecond timer to limit error window */
+static uint16_t RS485_Error_Timer = RS485_ERROR_TIMEOUT;
+/* number of errors in 1000ms before autobaud switching */
+#define RS485_ERROR_LIMIT 30
 
 /* The minimum time after the end of the stop bit of the final octet of a */
 /* received frame before a node may enable its EIA-485 driver: 40 bit times. */
@@ -141,6 +153,34 @@ bool RS485_Set_Baud_Rate(uint32_t baud)
     return valid;
 }
 
+void RS485_Next_Baud_Rate(void)
+{
+    uint32_t baud;
+
+    switch (RS485_Baud) {
+        case 9600:
+            baud = 19200;
+            break;
+        case 19200:
+            baud = 38400;
+            break;
+        case 38400:
+            baud = 57600;
+            break;
+        case 57600:
+            baud = 76800;
+            break;
+        case 76800:
+            baud = 115200;
+            break;
+        case 115200:
+        default:
+            baud = 9600;
+            break;
+    }
+    RS485_Set_Baud_Rate(baud);
+}
+
 /****************************************************************************
 * DESCRIPTION: Waits on the SilenceTimer for 40 bits.
 * RETURN:      none
@@ -201,6 +241,9 @@ void RS485_LED_Timers(void)
             BIT_SET(PORTD,PD7);
         }
     }
+    if (RS485_Error_Timer) {
+        RS485_Error_Timer--;
+    }
 }
 
 /****************************************************************************
@@ -263,7 +306,7 @@ void RS485_Send_Data(
 /****************************************************************************
 * DESCRIPTION: Return true if a framing or overrun error is present
 * RETURN:      true if error
-* ALGORITHM:   none
+* ALGORITHM:   autobaud - if there are a lot of errors, switch baud rate
 * NOTES:       Clears any error flags.
 *****************************************************************************/
 bool RS485_ReceiveError(void)
@@ -285,6 +328,34 @@ bool RS485_ReceiveError(void)
         do {
             dummy_data = UDR0;
         } while (BIT_CHECK(UCSR0A,RXC0));
+        /* count errors during autobaud */
+        if (RS485_Error_Count < RS485_ERROR_LIMIT) {
+            RS485_Error_Count++;
+        } else {
+            if (RS485_Autobaud && RS485_Error_Timer) {
+                /* We are in autobaud mode, and there were excessive 
+                   errors while the timer was counting down */
+                RS485_Next_Baud_Rate();
+                RS485_Error_Timer = RS485_ERROR_TIMEOUT;
+                RS485_Error_Count = 0;
+            } else if (RS485_Autobaud) {
+                /* autobaud, but timer expired */
+                RS485_Autobaud = false;
+            }
+        }
+    } else {
+       if (RS485_Autobaud) {
+           if ((RS485_Error_Timer == 0) && (RS485_Error_Count == 0)) {
+               if (RS485_Data_Count > 8) {
+                   /* no errors, timer expired, and we saw data */
+                   RS485_Autobaud = false;
+               } else {
+                   /* no errors, timer expired, and no data*/
+                   RS485_Error_Timer = RS485_ERROR_TIMEOUT;
+               }
+           }
+       }
+
     }
     
     return ReceiveError;
@@ -305,6 +376,8 @@ bool RS485_DataAvailable(uint8_t *data)
         *data = UDR0;
         DataAvailable = true;
         RS485_LED1_On();
+        if (RS485_Data_Count < 0xFF)
+            RS485_Data_Count++;
     }
 
     return DataAvailable;