Моя реализация функции приема xmodem не работает

Я хотел бы попросить совета о моем коде и показать вашу модель реализации.
Я реализую программу в коде ниже, и сделать этот код основа.

Теперь я реализовал функцию приемника для xmodem, но она не работает.

«xmodem_receive» вызывается в основной функции только после того, как напечатал «Отправка C ping ….» как printf и, готово.

Отправка xmodem работает так, как показано ниже.

Прием Xmodem не работает. Он закончен до получения данных.

Поэтому я хотел бы спросить

1) Почему моя функция получения xmodem не работает?

2) Почему STX присутствует как «K», и это может пройти через оператор IF

            if(recSTX == X_STX){
printf("STX is %c\n", &recSTX);
}else{
printf("Garabage payload %c\n", &recSTX);
}

Это моя функция реализации

static int xmodem_receive(int serial_fd, char* filename, int _crc){
int skip = 0;
uint8_t sdCRC = 'C';
uint8_t sdACK = X_ACK;
uint8_t eof = X_EOF;
uint8_t sdNAK = X_NAK;
uint8_t recSTX; // receive SOH from chunk
uint8_t recBlk; // receive blk from chunk
uint8_t recNegBlk; // receive blk negative from chunk
uint8_t recData[1024]; // receive data from chunk
uint16_t recChksum;
FILE *fp;
int ret, fd;
struct stat stat;
// If we want to receive, We have to send NAK to Sendor./* Writing as binary */
fp = fopen(filename, "wb");
//Send NAK still read SOH that header of one data chunks
while(1){
char status;
printf("Waiting for sender ping ...");
fflush(stdout);
//
do {
if(_crc){
printf("Send C ping....\n");
ret = write(serial_fd, &sdCRC, sizeof(sdCRC));
}else{
// send NAK before read SOH
printf("Send NAK ping....\n");
ret = write(serial_fd, &sdNAK, sizeof(sdNAK));
}    // after sending NAK,receiving　SOH from chunk
fflush(stdout);
ret = read(serial_fd, &recSTX, sizeof(recSTX));if(recSTX == X_STX){
printf("STX is %c\n", &recSTX);
}else{
printf("Garabage payload %c\n", &recSTX);
}
fflush(stdout);
if (ret != sizeof(recSTX)) {
printf("Not working");
fflush(stdout);
perror("read");
return -errno;
}
} while (recSTX != X_STX);

//So next, receiving blk
ret = read(serial_fd, &recBlk, sizeof(recBlk));
printf("Block Num is %d\n", recBlk);
fflush(stdout);
if (ret != sizeof(recBlk)) {
perror("read");
return -errno;
}
ret = read(serial_fd, &recNegBlk, sizeof(recNegBlk));
printf("Negative Block Num is %d\n", recNegBlk);
fflush(stdout);
if (ret != sizeof(recNegBlk)) {
perror("read");
return -errno;
}
ret = read(serial_fd, (void *)&recData, sizeof(recData));
printf("Data buffer is %c\n", &recData);
fflush(stdout);
if (ret != sizeof(recData)) {
perror("read");
return -errno;
}
ret = read(serial_fd, &recChksum, sizeof(recChksum));
printf("Check sum is %c", &recChksum);
fflush(stdout);
if (ret != sizeof(recChksum)) {
perror("read");
return -errno;
}
// data block number check
if(recBlk == 0xff - recNegBlk){
perror("read");
return -errno;
}
// data integrity check
if(recChksum == swap16(crc16(recData, sizeof(recData)))){
perror("read");
return -errno;
}
// check of appended "0xff" from end of data to  end of chunk in chunk
unsigned char *ptr = recData;
ptr += sizeof(recData);
while(*ptr == 0xff){
ptr--;
}
fwrite(recData, (ptr - recData),1,fp); // write Datas bytes from our buffer
// set skip flag or end connect
ret = write(serial_fd, &eof, sizeof(uint8_t));
if (ret != sizeof(eof) || ret != sizeof(X_STX)){
return -errno;
}else{
if(ret == X_STX){
skip = 1;
}else if(ret == EOF){
printf("EOF ...");
ret = write(serial_fd, &sdACK, sizeof(sdACK));
break;
}else{
return -errno;
}
}

}
printf("done.\n");
fclose(fp);
return 0;

}

И это полный код.

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <string.h>
#include <errno.h>
#include <unistd.h>
#include <fcntl.h>
#include <termios.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/mman.h>
#include <string>

#define X_STX 0x02
#define X_ACK 0x06
#define X_NAK 0x15
#define X_EOF 0x04

#define min(a, b)       ((a) < (b) ? (a) : (b))

struct xmodem_chunk {
uint8_t start;
uint8_t block;
uint8_t block_neg;
uint8_t payload[1024];
uint16_t crc;
} __attribute__((packed));

#define CRC_POLY 0x1021
static uint16_t crc_update(uint16_t crc_in, int incr)
{
uint16_t xor1 = crc_in >> 15;
uint16_t out1 = crc_in << 1;

if(incr)
out1++;

if(xor1)
out1 ^= CRC_POLY; // xor 0b1000000100001

return out1;
}static uint16_t crc16(const uint8_t *data, uint16_t size)
{
uint16_t crc, i;

for (crc = 0; size > 0; size--, data++)
for (i = 0x80; i; i >>= 1)
crc = crc_update(crc, *data & i);

for (i = 0; i < 16; i++)
crc = crc_update(crc, 0);

return crc;
}

static uint16_t swap16(uint16_t in)
{
return (in >> 8) | ((in & 0xff) << 8);
}

enum {
PROTOCOL_XMODEM,
PROTOCOL_YMODEM,
};

static int xmodem_receive(int serial_fd, char* filename, int _crc){
int skip = 0;
uint8_t sdCRC = 'C';
uint8_t sdACK = X_ACK;
uint8_t eof = X_EOF;
uint8_t sdNAK = X_NAK;
uint8_t recSTX; // receive SOH from chunk
uint8_t recBlk; // receive blk from chunk
uint8_t recNegBlk; // receive blk negative from chunk
uint8_t recData[1024]; // receive data from chunk
uint16_t recChksum;
FILE *fp;
int ret, fd;
struct stat stat;
// If we want to receive, We have to send NAK to Sendor./* Writing as binary */
fp = fopen(filename, "wb");
//Send NAK still read SOH that header of one data chunks
while(1){
char status;
printf("Waiting for sender ping ...");
fflush(stdout);
//
do {
if(_crc){
printf("Send C ping....\n");
ret = write(serial_fd, &sdCRC, sizeof(sdCRC));
}else{
// send NAK before read SOH
printf("Send NAK ping....\n");
ret = write(serial_fd, &sdNAK, sizeof(sdNAK));
}    // after sending NAK,receiving　SOH from chunk
fflush(stdout);
ret = read(serial_fd, &recSTX, sizeof(recSTX));if(recSTX == X_STX){
printf("STX is %c\n", &recSTX);
}else{
printf("Garabage payload %c\n", &recSTX);
}
fflush(stdout);
if (ret != sizeof(recSTX)) {
printf("Not working");
fflush(stdout);
perror("read");
return -errno;
}
} while (recSTX != X_STX);

//So next, receiving blk
ret = read(serial_fd, &recBlk, sizeof(recBlk));
printf("Block Num is %d\n", recBlk);
fflush(stdout);
if (ret != sizeof(recBlk)) {
perror("read");
return -errno;
}
ret = read(serial_fd, &recNegBlk, sizeof(recNegBlk));
printf("Negative Block Num is %d\n", recNegBlk);
fflush(stdout);
if (ret != sizeof(recNegBlk)) {
perror("read");
return -errno;
}
ret = read(serial_fd, (void *)&recData, sizeof(recData));
printf("Data buffer is %c\n", &recData);
fflush(stdout);
if (ret != sizeof(recData)) {
perror("read");
return -errno;
}
ret = read(serial_fd, &recChksum, sizeof(recChksum));
printf("Check sum is %c", &recChksum);
fflush(stdout);
if (ret != sizeof(recChksum)) {
perror("read");
return -errno;
}
// data block number check
if(recBlk == 0xff - recNegBlk){
perror("read");
return -errno;
}
// data integrity check
if(recChksum == swap16(crc16(recData, sizeof(recData)))){
perror("read");
return -errno;
}
// check of appended "0xff" from end of data to  end of chunk in chunk
unsigned char *ptr = recData;
ptr += sizeof(recData);
while(*ptr == 0xff){
ptr--;
}
fwrite(recData, (ptr - recData),1,fp); // write Datas bytes from our buffer
// set skip flag or end connect
ret = write(serial_fd, &eof, sizeof(uint8_t));
if (ret != sizeof(eof) || ret != sizeof(X_STX)){
return -errno;
}else{
if(ret == X_STX){
skip = 1;
}else if(ret == EOF){
printf("EOF ...");
ret = write(serial_fd, &sdACK, sizeof(sdACK));
break;
}else{
return -errno;
}
}

}
printf("done.\n");
fclose(fp);
return 0;

}

static int xymodem_send(int serial_fd, const char *filename, int protocol, int wait)
{
size_t len;
int ret, fd;
uint8_t answer;
struct stat stat;
const uint8_t *buf;
uint8_t eof = X_EOF;
struct xmodem_chunk chunk;
int skip_payload = 0;

fd = open(filename, O_RDONLY);
if (fd < 0) {
perror("open");
return -errno;
}

fstat(fd, &stat);
len = stat.st_size;
buf = static_cast<uint8_t*>(mmap(NULL, len, PROT_READ, MAP_PRIVATE, fd, 0));
if (!buf) {
perror("mmap");
return -errno;
}

if (wait) {
printf("Waiting for receiver ping ...");
fflush(stdout);

do {
ret = read(serial_fd, &answer, sizeof(answer));
if (ret != sizeof(answer)) {
perror("read");
return -errno;
}
} while (answer != 'C');

printf("done.\n");
}

printf("Sending %s ", filename);

if (protocol == PROTOCOL_YMODEM) {
strncpy((char *) chunk.payload, filename, sizeof(chunk.payload));
chunk.block = 0;
skip_payload = 1;
} else {
chunk.block = 1;
}

chunk.start = X_STX;

while (len) {
size_t z = 0;
int next = 0;
char status;

if (!skip_payload) {
z = min(len, sizeof(chunk.payload));
memcpy(chunk.payload, buf, z);
memset(chunk.payload + z, 0xff, sizeof(chunk.payload) - z);
} else {
skip_payload = 0;
}

chunk.crc = swap16(crc16(chunk.payload, sizeof(chunk.payload)));
chunk.block_neg = 0xff - chunk.block;

ret = write(serial_fd, &chunk, sizeof(chunk));
if (ret != sizeof(chunk))
return -errno;

ret = read(serial_fd, &answer, sizeof(answer));
if (ret != sizeof(answer))
return -errno;
switch (answer) {
case X_NAK:
status = 'N';
break;
case X_ACK:
status = '.';
next = 1;
break;
default:
status = '?';
break;
}

printf("%c", status);
fflush(stdout);

if (next) {
chunk.block++;
len -= z;
buf += z;
}
}

ret = write(serial_fd, &eof, sizeof(eof));
if (ret != sizeof(eof))
return -errno;

/* send EOT again for YMODEM */
if (protocol == PROTOCOL_YMODEM) {
ret = write(serial_fd, &eof, sizeof(eof));
if (ret != sizeof(eof))
return -errno;
}

printf("done.\n");

return 0;
}

static int open_serial(const char *path, int baud)
{
int fd;
struct termios tty;

fd = open(path, O_RDWR | O_SYNC);
if (fd < 0) {
perror("open");
return -errno;
}

memset(&tty, 0, sizeof(tty));
if (tcgetattr(fd, &tty) != 0) {
perror("tcgetattr");
return -errno;
}

cfsetospeed(&tty, baud);
cfsetispeed(&tty, baud);

tty.c_cflag = (tty.c_cflag & ~CSIZE) | CS8;     // 8-bit chars
tty.c_iflag &= ~IGNBRK;                         // disable break processing
tty.c_lflag = 0;                                // no signaling chars, no echo,
// no canonical processing
tty.c_oflag = 0;                                // no remapping, no delays
tty.c_cc[VMIN]  = 1;                            // read doesn't block
tty.c_cc[VTIME] = 5;                            // 0.5 seconds read timeout

tty.c_iflag &= ~(IXON | IXOFF | IXANY);         // shut off xon/xoff ctrl

tty.c_cflag |= (CLOCAL | CREAD);                // ignore modem controls,
// enable reading
tty.c_cflag &= ~(PARENB | PARODD);              // shut off parity
tty.c_cflag &= ~CSTOPB;
tty.c_cflag &= ~CRTSCTS;

if (tcsetattr(fd, TCSANOW, &tty) != 0) {
perror("tcsetattr");
return -errno;
}

return fd;
}

static void dump_serial(int serial_fd)
{
char in;

for (;;) {
read(serial_fd, &in, sizeof(in));
printf("%c", in);
fflush(stdout);
}
}

#ifdef TEST_XMODEM_RECEIVE

#endif // TEST_XMODEM_RECEIVE

int main(int argc, char **argv)
{
int a, ret, serial_fd;

printf("STX: %c\n", X_STX);

printf("ACK: %c\n", X_ACK);

printf("NAK: %c\n", X_NAK);

printf("EOF: %c\n", X_EOF);

fflush(stdout);

serial_fd = open_serial("/dev/ttyUSB0", 115200);
if (serial_fd < 0)
return -errno;if(std::string(argv[2]) == "0" || std::string(argv[2]) == "0"){
ret = xymodem_send(serial_fd, argv[1], PROTOCOL_XMODEM, 1);
if (ret < 0)
return ret;
}

if(std::string(argv[2]) == "1"){
ret = xmodem_receive(serial_fd, argv[1], 1);
if (ret < 0)
return ret;
}return 0;
}

Спасибо за просмотр моих вопросов.