# HG changeset patch
# User ideenmodellierer
# Date 1561922758 -7200
# Node ID 31e471d607970beeba7d2b44257a73a472713bb7
# Parent  37ee61f93124fba9cc2cb6116e9a0624e41a3b82
Added start of frame detection for HUD data
In the previous impmenentation the reception and evaluation of 15 byte were used without start detection. As a result sensor data could be stuck in case the frame sequence does not match the structure (e.g. cause by an framing error).
To resolve this in case of an invalid checksumme in combination with a data lost detection a byte based reception is startet to detect the start of a frame using the break between two transmissions.
In addition a babbling idiot protecting has been added because a faulty hardware could have an impact on the OSTC operation (high interrupt load)

diff -r 37ee61f93124 -r 31e471d60797 Discovery/Src/tCCR.c
--- a/Discovery/Src/tCCR.c	Sun Jun 30 21:18:05 2019 +0200
+++ b/Discovery/Src/tCCR.c	Sun Jun 30 21:25:58 2019 +0200
@@ -46,15 +46,24 @@
     uint16_t checksum;
 } 	SIrLink;
 
-/* Private variables ---------------------------------------------------------*/
-SIrLink receiveHUD[2];
-uint8_t boolHUDdata = 0;
-uint8_t data_old__lost_connection_to_HUD = 1;
+#define HUD_BABBLING_IDIOT			(30u)		/* 30 Bytes received without break */
+#define HUD_RX_FRAME_LENGTH			(15u)		/* Length of a HUD data frame */
+#define HUD_RX_FRAME_BREAK_MS		(100u)		/* Time used to detect a gap between two byte receptions => frame start */
+#define HUD_RX_START_DELAY_MS		(500u)		/* Delay for start of RX function to avoid start of reception while a transmission is ongoing. */
+												/* Based on an assumed cycle time by the sensor of 1 second. Started at time of last RX */
 
-uint8_t receiveHUDraw[16];
+/* Private variables ---------------------------------------------------------*/
+static SIrLink receiveHUD[2];
+static uint8_t boolHUDdata = 0;
+static uint8_t data_old__lost_connection_to_HUD = 1;
 
-uint8_t StartListeningToUART_HUD = 0;
-uint16_t count = 0;
+static uint8_t receiveHUDraw[16];
+
+static uint8_t StartListeningToUART_HUD = 0;
+static uint16_t HUDTimeoutCount = 0;
+
+static __IO ITStatus UartReadyHUD = RESET;
+static uint32_t LastReceivedTick_HUD = 0;
 
 /* Private variables with external access via get_xxx() function -------------*/
 
@@ -289,36 +298,69 @@
     */
 void tCCR_tick(void)
 {
-    if(count < 3 * 10)
-        count++;
+    if(HUDTimeoutCount < 3 * 10)
+        HUDTimeoutCount++;
     else
     {
         data_old__lost_connection_to_HUD = 1;
-        if(count < 20 * 10)
-            count++;
+        if(HUDTimeoutCount < 20 * 10)
+            HUDTimeoutCount++;
         else
             tCCR_fallbackToFixedSetpoint();
     }
 }
 
+void tCCR_SetRXIndication(void)
+{
+	static uint8_t floatingRXCount = 0;
+
+	if((UartIR_HUD_Handle.RxXferSize == HUD_RX_FRAME_LENGTH) || (UartIR_HUD_Handle.RxXferSize == HUD_RX_FRAME_LENGTH - 1))	/* we expected a complete frame */
+	{
+		UartReadyHUD = SET;
+		LastReceivedTick_HUD = HAL_GetTick();
+		floatingRXCount = 0;
+	}
+	else	/* follow up of error handling */
+	{
+		if(time_elapsed_ms(LastReceivedTick_HUD, HAL_GetTick()) > HUD_RX_FRAME_BREAK_MS)	/* Reception took a while => frame start detected */
+		{
+			HAL_UART_Receive_IT(&UartIR_HUD_Handle, &receiveHUDraw[1], 14);					/* We have already the first byte => get the missing 14 */
+		}
+		else
+		{
+			if(floatingRXCount++ < HUD_BABBLING_IDIOT)
+			{
+				HAL_UART_Receive_IT(&UartIR_HUD_Handle, receiveHUDraw, 1);					/* Start polling of incoming bytes */
+			}
+			else																			/* Significant amount of data comming in without break => disable input */
+			{																				/* by not reactivation HUD RX, no recovery fromthis state */
+				stateUsedWrite->diveSettings.ppo2sensors_deactivated = 0x07;				/* Display deactivation */
+			}
+		}
+	}
+
+}
 
 void tCCR_restart(void)
 {
-    HAL_UART_Receive_IT(&UartIR_HUD_Handle, receiveHUDraw, 15);/* 15*/
+	HAL_UART_AbortReceive_IT(&UartIR_HUD_Handle);	/* Called by the error handler. RX will be restarted by control function */
+	StartListeningToUART_HUD = 1;
 }
 
 
 void tCCR_control(void)
 {
-    if((UartReadyHUD == RESET) && StartListeningToUART_HUD)
-    {
-            StartListeningToUART_HUD = 0;
-            HAL_UART_Receive_IT(&UartIR_HUD_Handle, receiveHUDraw, 15);/* 15*/
-    }
+
+	if((UartReadyHUD == RESET) && StartListeningToUART_HUD && (time_elapsed_ms(LastReceivedTick_HUD, HAL_GetTick()) > HUD_RX_START_DELAY_MS))
+	{
+		StartListeningToUART_HUD = 0;
+		HAL_UART_Receive_IT(&UartIR_HUD_Handle, receiveHUDraw, HUD_RX_FRAME_LENGTH);
+	}
 
     if(UartReadyHUD == SET)
     {
             UartReadyHUD = RESET;
+            StartListeningToUART_HUD = 1;
 
             memcpy(&receiveHUD[!boolHUDdata], receiveHUDraw, 11);
             receiveHUD[!boolHUDdata].battery_voltage_mV = receiveHUDraw[11] + (256 * receiveHUDraw[12]);
@@ -333,10 +375,18 @@
             if(checksum == receiveHUD[!boolHUDdata].checksum)
             {
                 boolHUDdata = !boolHUDdata;
-                count = 0;
+                HUDTimeoutCount = 0;
                 data_old__lost_connection_to_HUD = 0;
             }
-            StartListeningToUART_HUD = 1;
+            else
+            {
+            	if(data_old__lost_connection_to_HUD)	/* we lost connection, maybe due to RX shift => start single byte read to resynchronize */
+            	{
+            		HAL_UART_Receive_IT(&UartIR_HUD_Handle, receiveHUDraw, 1);
+            		StartListeningToUART_HUD = 0;
+            	}
+            }
+            memset(receiveHUDraw,0,sizeof(receiveHUDraw));
     }
 }