Update mcp_can.cpp

Maintain the deterministic timeout for sendMsg().
frubat · Nov 24, 2022 · c4b6fc0 · c4b6fc0
1 parent 2eca0ac
commit c4b6fc0
Showing 1 changed file with 12 additions and 9 deletions.
diff --git a/mcp_can.cpp b/mcp_can.cpp
@@ -1108,29 +1108,32 @@ INT8U MCP_CAN::clearMsg()
 INT8U MCP_CAN::sendMsg()
 {
     INT8U res, res1, txbuf_n;
-    uint16_t uiTimeOut = 0;
-
+    uint32_t uiTimeOut, temp;
+
+    temp = micros();
+    // 24 * 4 microseconds typical
     do {
         res = mcp2515_getNextFreeTXBuf(&txbuf_n);                       /* info = addr.                 */
-        uiTimeOut++;
+        uiTimeOut = micros() - temp;
     } while (res == MCP_ALLTXBUSY && (uiTimeOut < TIMEOUTVALUE));
 
-    if(uiTimeOut == TIMEOUTVALUE) 
+    if(uiTimeOut >= TIMEOUTVALUE) 
     {   
         return CAN_GETTXBFTIMEOUT;                                      /* get tx buff time out         */
     }
-    uiTimeOut = 0;
+    uiTimeOut = micros;
     mcp2515_write_canMsg( txbuf_n);
     mcp2515_modifyRegister( txbuf_n-1 , MCP_TXB_TXREQ_M, MCP_TXB_TXREQ_M );
 
+    temp = micros();
     do
-    {
-        uiTimeOut++;        
+    {       
         res1 = mcp2515_readRegister(txbuf_n-1);                         /* read send buff ctrl reg 	*/
-        res1 = res1 & 0x08;                               		
+        res1 = res1 & 0x08;
+	uiTimeOut = micros() - temp;
     } while (res1 && (uiTimeOut < TIMEOUTVALUE));   
 
-    if(uiTimeOut == TIMEOUTVALUE)                                       /* send msg timeout             */	
+    if(uiTimeOut >= TIMEOUTVALUE)                                       /* send msg timeout             */	
         return CAN_SENDMSGTIMEOUT;
 
     return CAN_OK;