Arduino Nano reading incorrect bytes

Projects Interfacing w/ Software on the Computer
1

Hello! I am trying to send some strings in raw binary from the computer to arduino nano using serial communication. On the PC side, I am using a c library "libserialport" from sigrokproject to manage the serial communication. I could have used linux termios but it is too low level for me. The problem is arduino reads incorrect values of bytes, when i send them from pc. I used start and stop markers to send the packets, but still no effect. What am i doing wrong pls help...
My PC program:

#include <libserialport.h>
#include <inttypes.h>
#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#define ID_STORE 1
#define ID_RETRIEVE 2
#define GENDER_STORE 3
#define GENDER_RETRIEVE 4
#define NAME_STORE 5
#define NAME_RETRIEVE 6

#define OK 10
#define NOT_OK 11
 
uint8_t recv_buf[50];

static int get_msg_len(char *msg) 
{
  int len = 0;
  while (msg[len] != '\n') {
    len++;
  }
  return len+1;
}

static struct sp_port *port_init(char *name) 
{
  struct sp_port *port;

  sp_get_port_by_name(name, &port);
  sp_open(port, SP_MODE_READ_WRITE);
  sleep(3);
  sp_set_baudrate(port, 9600);
  sp_set_bits(port, 8);
  sp_set_flowcontrol(port, SP_FLOWCONTROL_NONE);
  sp_set_parity(port, SP_PARITY_NONE);
  sp_set_stopbits(port, 1);
  sp_flush(port, SP_BUF_BOTH);

  return port;
}

static void port_exit(struct sp_port *port) 
{
  sp_free_port(port);
  sp_close(port);
}

static int port_start_transmission(struct sp_port *port, uint8_t mode) 
{
  uint8_t sop = '<', eop = '>';
  
  while (sp_output_waiting(port) > 0) usleep(2);
  sp_nonblocking_write(port, &sop, sizeof(sop));
  while (sp_output_waiting(port) > 0) usleep(2);
  sp_nonblocking_write(port, &mode, sizeof(mode));
  while (sp_output_waiting(port) > 0) usleep(2);
  sp_nonblocking_write(port, &eop, sizeof(eop));
  while (sp_output_waiting(port) > 0) usleep(2);
  sp_drain(port);
  
  uint8_t response[8];
  int done = 0;
  int inc = 0;
  int start = 0;
  while (!done) {
    if (sp_input_waiting(port) > 0) {
      uint8_t byte;
      sp_nonblocking_read(port, &byte, sizeof(byte));
      if (byte == sop) {
        start = 1;
        continue; 
      } else if (byte == eop) {
        done = 1;
        continue;
      }
      if (start) {
        response[inc++] = byte;
      }
    }
    usleep(2);
  }
  return response[0];
}

static int port_send_msg(struct sp_port *port, char *msg, int msg_len, uint8_t mode) 
{
  uint8_t sop = '<', eop = '>';
  msg[msg_len - 1] = '\0';
  int response = port_start_transmission(port, mode);
  
  if (response == OK) {
    int inc = 0;
    sp_nonblocking_write(port, &sop, sizeof(sop));
    while (msg_len) {
      sp_nonblocking_write(port, &msg[inc++], sizeof(msg[0]));
      while (sp_output_waiting(port) > 0) usleep(2);
      msg_len--;
    }  
    sp_nonblocking_write(port, &eop, sizeof(eop));
    while (sp_output_waiting(port) > 0) usleep(2);
    return 1;
  } else if (response == NOT_OK) {
    return 0;
  }
  return 0;
}

static int port_receive_msg(struct sp_port *port, uint8_t mode)  
{
  uint8_t sop = '<', eop = '>';
  int response = port_start_transmission(port, mode);

  if (response == OK) {
    int done = 0;
    int inc = 0;
    int start = 0;
    while (!done) {
      if (sp_input_waiting(port) > 0) {
        uint8_t byte;
        sp_nonblocking_read(port, &byte, sizeof(byte));
        if (byte == sop) {
          start = 1;
          continue; 
        } else if (byte == eop) {
          done = 1;
          continue;
        }
        if (start) {
          recv_buf[inc++] = byte;
        }
      }
      usleep(2);
    }
    return 1;
  } else if (response == NOT_OK) {
    return 0;
  } 
  return 0;
}

static void interface_store(struct sp_port *port) 
{
  int running = 1;
  while (running)
  {
    printf("1. Store name?\n"
           "2. Store id?\n"
           "3. Store gender?\n"
           "4. Go to main menu?\n\n"
          );
    printf("Enter a number: ");
    fflush(stdout);
    int num;
    scanf("%d", &num);
    getchar();
    printf("\n");
    char buf[50];
    int code;
    switch (num)
    {
      case 1:
        printf("Enter your name: \n");
        fgets(buf, sizeof(buf), stdin);
        printf("Sending info...\n");
        code = port_send_msg(port, buf, get_msg_len(buf), NAME_STORE);
        if (code)
          printf("Sent successfully! Press enter to continue...");
        else {
          printf("Sent unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 2:
        printf("Enter your id: \n");
        fgets(buf, sizeof(buf), stdin);
        printf("Sending info...\n");
        code = port_send_msg(port, buf, get_msg_len(buf), ID_STORE);
       if (code)
          printf("Sent successfully! Press enter to continue...");
        else {
          printf("Sent unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 3:
        printf("Enter your gender: \n");
        fgets(buf, sizeof(buf), stdin);
        printf("Sending info...\n");
        code = port_send_msg(port, buf, get_msg_len(buf), GENDER_STORE);
        if (code)
          printf("Sent successfully! Press enter to continue...");
        else {
          printf("Operation unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 4:
        running = 0;
        break;
      default:
        printf("Invalid number! Press enter to continue...");
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
    } 
  }
}

static void interface_retrieve(struct sp_port *port)
{
  int running = 1;
  while (running) {
    printf("1. Retrieve name?\n"
           "2. Retrieve id?\n"
           "3. Retrieve gender?\n"
           "4. Go to main menu?\n\n"
          );
    printf("Enter a number: ");
    fflush(stdout);
    int num;
    scanf("%d", &num);
    getchar();
    printf("\n");
    int code;
    switch (num)
    {
      case 1:
        printf("Retrieving info...\n");
        code = port_receive_msg(port, NAME_RETRIEVE);
        if (code)
          printf("Device owner name is: %s. Press enter to continue...", recv_buf);
        else {
          printf("Operation unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 2:
        printf("Retrieving info...\n");
        code = port_receive_msg(port, ID_RETRIEVE);
        if (code)
          printf("Device owner name is: %s. Press enter to continue...", recv_buf);
        else {
          printf("Operation unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 3:
        printf("Retrieving info...\n");
        code = port_receive_msg(port, GENDER_RETRIEVE);
        if (code)
          printf("Device owner name is: %s. Press enter to continue...", recv_buf);
        else {
          printf("Operation unsuccessful:( Press enter to continue...");
        }
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
      case 4:
        running = 0;
        break;
      default:
        printf("Invalid number! Press enter to continue...");
        fflush(stdout);
        getchar();
        system("clear");
        running = 1;
        break;
    } 
  }
}

static int interface_main(struct sp_port *port) 
{
  printf("1. Store operation?\n"
         "2. Retrieve operation?\n"
         "3. Exit?\n\n"
        );
  printf("Enter a number: ");
  fflush(stdout);
  int num;
  scanf("%d", &num);
  getchar();
  printf("\n\n");
  switch (num)
  {
    case 1:
      system("clear");
      interface_store(port);
      system("clear");
      return 1;
    case 2:
      system("clear");
      interface_retrieve(port);
      system("clear");
      return 1;
    case 3:
      return 0;
    default:
      printf("Invalid number! Press enter to continue...");
      fflush(stdout);
      getchar();
      system("clear");
      return 1;
  }
}

static void main_loop() 
{
  int running = 1;
  struct sp_port *port = port_init("/dev/ttyUSB0");
  
  while(running) {
    running = interface_main(port);
  }

  port_exit(port);
}

int main(int argc, char **argv) 
{
  // Starting point. Process events, shows interface. Can run forever if no exit msg received from user.
  main_loop(); 
  return 0;
}

The code running on Arduino:

#define ID_STORE 1
#define ID_RETRIEVE 2
#define GENDER_STORE 3
#define GENDER_RETRIEVE 4
#define NAME_STORE 5
#define NAME_RETRIEVE 6

#define OK 1
#define NOT_OK 0

byte id[50];
byte gender[50];
byte name[50];
byte buf[50];

int get_len(byte *msg) {
  int len = 0;
  while (msg[len] != '\0') {
    len++;
  }
  return len + 1;
}

int confirm_transmission() {
  byte sop = '<', eop = '>';
  
  int done = 0;
  int inc = 0;
  int start = 0;
  byte response[8];
  memset(response, 0, sizeof(response));
  while (!done) {
    if (Serial.available() > 0) {
      byte val = Serial.read();
      digitalWrite(LED_BUILTIN, HIGH);
      if (val == sop) {
        start = 1;
        continue; 
      } else if (val == eop) {
        done = 1;
        continue;
      }
      if (start) {
        response[inc++] = val;
      }
    }
  }
  
  if (response[0] == 0) {
    while (Serial.availableForWrite() <= 0);
    Serial.write(sop);
    while (Serial.availableForWrite() <= 0);
    Serial.write(NOT_OK);
    while (Serial.availableForWrite() <= 0);
    Serial.write(eop);
    while (1); 
  } else {
    while (Serial.availableForWrite() <= 0);
    Serial.write(sop);
    while (Serial.availableForWrite() <= 0);
    Serial.write(OK);
    while (Serial.availableForWrite() <= 0);
    Serial.write(eop);
    return response[0];
  }
}

void send_msg(byte *msg) {
  byte sop = '<', eop = '>';
  while (Serial.availableForWrite() <= 0);
  Serial.write(sop);
  int len = get_len(msg);
  int inc = 0;
  while (len) {
    while (Serial.availableForWrite() <= 0);
    Serial.write(msg[inc++]);
    len--;
  }
  while (Serial.availableForWrite() <= 0);
  Serial.write(eop);
}

void recv_msg() {
  byte sop = '<', eop = '>';
  int done = 0;
  int inc = 0;
  int start = 0;
  while (!done) {
    if (Serial.available() > 0) {
      byte val = Serial.read();
      if (val == sop) {
        start = 1;
        continue; 
      } else if (val == eop) {
        done = 1;
        continue;
      }
      if (start) {
        buf[inc++] = val;
      }
    }
  }
}

void fill_id(byte *msg) {
  int inc = 0;
  while (msg[inc] != '\0') {
    id[inc] = msg[inc];
    inc++;
  }
  id[inc] = '\0';
}

void fill_gender(byte *msg) {
  int inc = 0;
  while (msg[inc] != '\0') {
    gender[inc] = msg[inc];
    inc++;
  }
  gender[inc] = '\0';
}

void fill_name(byte *msg) {
  int inc = 0;
  while (msg[inc] != '\0') {
    name[inc] = msg[inc];
    inc++;
  }
  name[inc] = '\0';
}

void setup() {
  Serial.begin(1200);
  pinMode(LED_BUILTIN, OUTPUT);
}

void loop() {
  int mode = confirm_transmission();
  switch (mode) {
    case ID_STORE:
      recv_msg();
      fill_id(buf);
      break;
    case GENDER_STORE:
      recv_msg();
      fill_gender(buf);
      break;
    case NAME_STORE:
      recv_msg();
      fill_name(buf);
      break;
    case ID_RETRIEVE:
      send_msg(id);
      break;
    case GENDER_RETRIEVE:
      send_msg(gender);
      break;
    case NAME_RETRIEVE:
      send_msg(name);
      break;
    default:
      break;
  }
}
2

To verify that the NANO is receiving string correctly, use IDE/Serial Monitor as a test jig.

3

Maybe this is the issue?

4

I already did that. Now the funny thing is when i send only a single byte over serial arduino seems to send back the correct value.

5

i tried with 9600 baud with both arduino and pc still nothing happens.

6

It compiles and works fine after I change both values to 9600.

When I add some debugging information here (after changing both baud rates to 9600):

I see:

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 1

Enter your name: 
name
Sending info...
<

>
Sent unsuccessful:( Press enter to continue...

Which makes me suspect that the serial communication itself is fine, but there is something wrong with the logic.

Maybe this has something to do with it?

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 1

Enter your name: 
name
Sending info...
Sent successfully! Press enter to continue...

After defining OK 1 and NOT_OK 0 in your C file.

7

(post deleted by author)

8

nope still stuck at sending info....even after fixing those mistakes

9

Well, I am not making it up.

1. Store operation?
2. Retrieve operation?
3. Exit?

Enter a number: 1

---

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 1

Enter your name: 
name
Sending info...
Sent successfully! Press enter to continue...

---

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 2

Enter your id: 
1
Sending info...
Sent successfully! Press enter to continue...

---

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 3

Enter your gender: 
G
Sending info...
Sent successfully! Press enter to continue...

---

1. Store name?
2. Store id?
3. Store gender?
4. Go to main menu?

Enter a number: 4

---

1. Store operation?
2. Retrieve operation?
3. Exit?

Enter a number: 2

---

1. Retrieve name?
2. Retrieve id?
3. Retrieve gender?
4. Go to main menu?

Enter a number: 1

Retrieving info...
Device owner name is: name. Press enter to continue...

---

1. Retrieve name?
2. Retrieve id?
3. Retrieve gender?
4. Go to main menu?

Enter a number: 2

Retrieving info...
Device owner name is: 1. Press enter to continue...

---

1. Retrieve name?
2. Retrieve id?
3. Retrieve gender?
4. Go to main menu?

Enter a number: 3

Retrieving info...
Device owner name is: G. Press enter to continue...

---

1. Retrieve name?
2. Retrieve id?
3. Retrieve gender?
4. Go to main menu?

Enter a number: 4

---

1. Store operation?
2. Retrieve operation?
3. Exit?

Enter a number: 3

[edit]

Are you using the correct serial port (perhaps it should be /dev/ttyACM0)?

10

Sorry the only port that shows up when i connect arduino to my computer is /dev/ttyUSB0 and occasionally maybe /dev/ttyUSB1. No /dev/ttyACM0