Bug in FT8 Telemetry mode and an easy fix. (Atmel tool chain and possibly others)

[SquirrelEng]

There is a bug in the FT8 telemetry mode code.

In JTEncode.cpp line 887 the line: snprintf(temp_msg, 19, "%*s", 18, c18); sets temp_msg to a zero length string. This causes the variable "message" further down in the code to have a zero 1st byte and corrupts the telemetry message.

Replace the snprintf call with the following: snprintf(temp_msg, 19, "%18s", c18);

I am running the code on an Arduno Pro Mini (Atmel chip) and it appears that the %*s formatter is not functioning correctly on this tool chain. Since the length is hard coded, the simpler %18s will work.

73s de KJ6FO

[NT7S]

Thank you very much, I will check this soon and push the change when I can verify the fix.

[sajjsamm]

I have the same problem with Arduino and bluepill too. in decoding the message with WSJT-X the last char of message is getting truncated. the SquirrelEng solution didn't work for me.

[dl9sau]

I had the same problem.

Plus another problem: a normal message like "73 DL9SAU" is interpreted as hex telemetry. The code checks for hex until blank. If blank is reached, or end of string, the function ends. It has detected at this stage "73" as hex string. -> 0x73..... (rest are fill characters) are transmitted.

Furthermore, there is much useless copying aroound array c18.

-> This fixes the issues:

--- a/src/JTEncode.cpp
+++ b/src/JTEncode.cpp
@@ -839,9 +839,9 @@ void JTEncode::ft8_bit_packing(char* message, uint8_t* codeword)
    uint8_t n3 = 0;
    uint8_t qa[10];
    uint8_t qb[10];
-   char c18[19];
+   //char c18[19];
    bool telem = false;
-   char temp_msg[19];
+   //char temp_msg[19];
    memset(qa, 0, 10);
    memset(qb, 0, 10);

@@ -852,10 +852,14 @@ void JTEncode::ft8_bit_packing(char* message, uint8_t* codeword)
    // Has to be hex digits, can be no more than 18
    for(i = 0; i < 19; ++i)
    {
-       if(message[i] == 0 || message[i] == ' ')
+       //if(message[i] == 0 || message[i] == ' ')
+       if(message[i] == 0)
        {
            break;
        }
+       // bugfix: "73     DL9SAU" was interpreted as hex message. Check further for non-hex-character
+       else if (message[i] == ' ')
+           continue;
        else if(hex2int(message[i]) == -1)
        {
            telem = false;
@@ -863,7 +867,7 @@ void JTEncode::ft8_bit_packing(char* message, uint8_t* codeword)
        }
        else
        {
-           c18[i] = message[i];
+           // c18[i] = message[i]; // not necessary. only if telemetry, it's used. First thing done below is, set c18 to 0.
            telem = true;
        }
    }
@@ -882,6 +886,7 @@ void JTEncode::ft8_bit_packing(char* message, uint8_t* codeword)
            }
        }

+#ifdef notdef
        memset(c18, 0, 19);
        memmove(c18, message, i0 + 1);
        snprintf(temp_msg, 19, "%*s", 18, c18);
@@ -895,7 +900,10 @@ void JTEncode::ft8_bit_packing(char* message, uint8_t* codeword)
          }
        }
        strcpy(message, temp_msg);
-
+#else
+       for (char *p = message; *p; p++)
+           if (islower(*p)) *p = toupper(*p);
+#endif

        uint8_t temp_int;
        temp_int = message[0] == ' ' ? 0 : hex2int(message[0]);