fix wrongly disallowed rx of max possible size

TinyFrame.c

@@ -485,6 +485,7 @@ void _TF_FN TF_AcceptChar(TinyFrame *tf, unsigned char c)
     }
 #endif
 
+    //@formatter:off
     switch (tf->state) {
         case TFState_SOF:
             if (c == TF_SOF_BYTE) {
@@ -536,6 +537,7 @@ void _TF_FN TF_AcceptChar(TinyFrame *tf, unsigned char c)
                 }
 
                 if (tf->len == 0) {
+                    // if the message has no body, we're done.
                     TF_HandleReceivedMessage(tf);
                     TF_ResetParser(tf);
                     break;
@@ -547,7 +549,7 @@ void _TF_FN TF_AcceptChar(TinyFrame *tf, unsigned char c)
 
                 CKSUM_RESET(tf->cksum); // Start collecting the payload
 
-                if (tf->len >= TF_MAX_PAYLOAD_RX) {
+                if (tf->len > TF_MAX_PAYLOAD_RX) {
                     // ERROR - frame too long. Consume, but do not store.
                     tf->discard_data = true;
                 }
@@ -588,6 +590,7 @@ void _TF_FN TF_AcceptChar(TinyFrame *tf, unsigned char c)
             }
             break;
     }
+    //@formatter:on
 
     // we get here after finishing HEAD, if no data are to be received - handle and clear
     if (tf->len == 0 && tf->state == TFState_DATA) {
@@ -771,6 +774,8 @@ static bool _TF_FN TF_SendFrame(TinyFrame *tf, TF_Msg *msg, TF_Listener listener
         }
     }
 
+    // Checksum only if message had a body
+    if (msg->len > 0) {
         // Flush if checksum wouldn't fit in the buffer
         if (TF_SENDBUF_LEN - len < sizeof(TF_CKSUM)) {
             TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
@@ -779,8 +784,9 @@ static bool _TF_FN TF_SendFrame(TinyFrame *tf, TF_Msg *msg, TF_Listener listener
 
         // Add checksum, flush what remains to be sent
         len += TF_ComposeTail(tf->sendbuf + len, &cksum);
-    TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
+    }
 
+    TF_WriteImpl(tf, (const uint8_t *) tf->sendbuf, len);
     TF_ReleaseTx(tf);
 
     return true;

TinyFrame.h

@@ -10,7 +10,7 @@
  * Upstream URL: https://github.com/MightyPork/TinyFrame
  */
 
-#define TF_VERSION "2.0.2"
+#define TF_VERSION "2.0.4"
 
 //---------------------------------------------------------------------------
 #include <stdint.h>  // for uint8_t etc