Read away trash coming before slave id

Author: budulinek

arduino-modbus-rtu-tcp-gateway/03-modbus-rtu.ino

@@ -127,13 +127,13 @@ void recvSerial() {
   static byte serialIn[MODBUS_SIZE];
   while (mySerial.available() > 0) {
     byte b = mySerial.read();
-    if (rxNdx == 0 && queueData[0] != b) {
-      if(recvMicroTimer.isOver())
+    if (rxNdx == 0 && queueData[0] != b) { // TODO maybe duplicate check? See the check bellow.
+      if (recvMicroTimer.isOver())
         break;
       // wait a bit to the buffer to clean up
-      recvMicroTimer.sleep(charTimeOut());  
-    }
-    else if (rxNdx < MODBUS_SIZE) {
+      recvMicroTimer.sleep(charTimeOut());
+      data.errorCnt[ERROR_RTU]++;
+    } else if (rxNdx < MODBUS_SIZE) {
       serialIn[rxNdx] = b;
       rxNdx++;
     }  // if frame longer than maximum allowed, CRC will fail and data.errorCnt[ERROR_RTU] will be recorded down the road

arduino-modbus-rtu-tcp-gateway/arduino-modbus-rtu-tcp-gateway.ino

@@ -27,9 +27,10 @@
   v7.3 2024-01-16 Bugfix Modbus RTU Request form, code comments
   v7.4 2024-12-16 CSS improvement, code optimization, simplify DHCP renew, better README (solution to ethernet reset issue)
   v8.0 2025-03-09 Fix 404 error page, code optimization
+  v8.1 2025-03-30 Read away trash coming before slave id
 */
 
-const byte VERSION[] = { 8, 0 };
+const byte VERSION[] = { 8, 1 };
 
 #include <SPI.h>
 #include <Ethernet.h>