fix: Fixes #2

Author: epsilonrt

src/Modbus.cpp

@@ -414,7 +414,7 @@ void Modbus::readCoils (word startreg, word numregs) {
   byte bitn = 0;
   word totregs = numregs;
   word i;
-  while (numregs--) {
+  while (numregs) {
     i = (totregs - numregs) / 8;
     if (coil (startreg)) {
       bitSet (_frame[2 + i], bitn);
@@ -423,12 +423,10 @@ void Modbus::readCoils (word startreg, word numregs) {
       bitClear (_frame[2 + i], bitn);
     }
     //increment the bit index
-    bitn++;
-    if (bitn == 8) {
-      bitn = 0;
-    }
+    bitn = (bitn + 1) % 8;
     //increment the register
     startreg++;
+    numregs--;
   }
 
   _reply = MB_REPLY_NORMAL;