Char string overwriteing other string - c

Question

I´m making a program that builds a binary message. I´m using char strings to hold the binary value. So I´ve initialized a bunch of char strings that has the default values. Then I combine them by running a for loop and read them into a large string (aismsg/ais_packet). And everything worked fine untill I added msg14Text[], then the string I´m building (aismsg/ais_packet) gets shortened as shown below (even though I´m not using the variable). Seems like when I add msg14Text[], it changes the value of one of the other strings. Is this maybe a memory allocation problem?
Part of the code:
char ais_packet[257]; //Allokerer array for ais data pakke.
char aismsg[175]; //Allokerer array for meldingen.
int burst_nr = 1; //Indicates with burst it is transmittin (1-7).
char ramp_up[] = "00000000"; //Ramp up buffer.
char train_seq[] = "010101010101010101010101"; //Training sequence 24 bits of alternating 0-1.s
char hdlc_flag[] = "01111110"; //HDLC Start and END flag.
char buffer[] = "000000000000000000000000"; //Data packet buffer.
char msgID1[] = "000001"; //msg. 1.
char msgID14[] ="010100"; //msg. 14.
char repeat[] = "00"; //repetert 0 ganger.
char mmsi[] = "000111010110111100110100010101"; //Gir 123456789 som MMSI.
char nav_stat[] = "1111"; //Gir 15= AIS-SART test, endres til 14 (1110) for aktiv AIS-SART.x'
char rot[] = "10000000"; //Rate of Turn -128 betyr ikkje tilgjengelig.
char sogBin[] = "1111111111"; //Tilsvarer 1023 = not available = default.
char pos_acc[] = "0"; //Posisjonsnøyaktighet over 10m. 1 = under 10m.
char lonBin[] = "0110011110010001101011000000"; // Tilsvarer 181 grader som er default verdi for Longitude.
char latBin[] = "011010000010010000101000000"; // Tilsvarer 91 grader som er default verdi for Latitude.
char cogBin[] = "111000010000"; //Tilsvarer 3600 = not available = default.
char headingBin[] = "111111111"; //511 = not available = default
char timestamp[] = "111100"; //Tid siden melding er generert, 60 = default = ts not available.
char spec_man[] = "01"; //Special manouver 0 = default, 1 = not engaged in special manouver
char spare[] = "000";
char spareMSG14[] = "00"; //Reserved.
char raim[] = "0"; //RAIM 0 = not in use.
char comm_state[] = "00011100000000000000"; // First 2bit: Sync state: 3 = no UTC sync = default, 0 = UTC sync. 0011100000000000000
char msg14Text[] = "100100101101111011111100"; //CAUSING TROUBLE!!!! for AIS melding 14 står "Test" med 6-bit ASCII koding.
The enitre code for the function can be found at pastebin.com/wj0RxyLX
Output of ais packet with msg14Text[]:
00000000
Output of ais packet without msg14Text[]:
0000000001010101010101010101010101111110000001000001110101101111001101000101011111100000000011010000000000000110100011000101111000000101100100000100001100101110000100000000110011111000100000011100000000000000001000100110100101111110000000000000000000000000
aispacket should consist of the following variables:
ramp_up[] + train_seq[] + hdlc_flag[] + Datapacket(168bit) + crc(16bit) + hdlc_flag[] + buffer[] + '\0'

Answer 1

"Is this maybe a memory allocation problem?"
You don't explicitly allocate any memory in your code. Note that char repeat[] = "00"; is statically allocated array whose size is equal to size of 3 chars and whose content is being initialized by string literal "00".
Problem is most likely in copying of these strings into ais_packet since you do that in nonstandard way (character by character) which causes your code to be hard to read and it's quite easy to make a mistake there:
for(int k=0; k<256; k++)
{
...
if(k==256) // are you sure that value of k will reach 256 ?
I recommend you to use C-style functions that have been created for this purpose: Craete ais_packet by copying first string into it by using strcpy and keep extending content of this ais_packet by appending other strings by using strcat.
This question will also help you: Using strcat in C

Answer 2

At the end of the ugly for (k=0; k < 168; k++) { if ... else if ...} loop
else if(k==168)
{
aismsg[k] = '\0';
k=0;
}
This will make either (k <=168) the loop run forever, or (k <168) never be executed. (there are more instances of this pattern)
BTW another way to do the same (also faster) would be
....
unsigned dst=0;
memcpy (array+dst, src1, 123);
dst += 123;
memcpy(array+dst, src2, 234);
dst += 234;
...
array[dst] = 0;

Answer 3

Just a thought, but if you are building binary messages, why not use actual binary instead of char arrays? Here's a way to use structs inside a union to bit pack binary data.
// declaration
typedef union
{
uint32_t packed;
struct {
uint16_t sample1: 12; // 12 bits long
uint16_t sample2: 14;
uint16_t 6; // unused bits
} data;
} u1;
// instantiation
u1 pack1;
// setting
pack1.data.sample1 = 1234;
//getting
uint16_t newval = pack1.data.sample2;
// setting bit 6 in sample 1
pack1.data.sample1 |= (1 << 6);
// setting lo nibble in sample1 to 0101
pack1.data.sample1 &= 0b11110101;
// getting the whole packed value
uint32_t binmsg = pack1.packed;