Termios c++ serial read not reading arduino serial - c++

Question

I am trying to read serial data from an Arduino Uno. I am using the Termios struct and followed this tutorial. I am not receiving the Arduino serial data in return, can anyone help me? First time using c++ to read serial. Following is the c++ code (i'm using ROS), and the arduino code.
c++ code
#include <ros.h>
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <termios.h>
#include <csignal>
#include <sstream>
#include <algorithm>
#include <iterator>
const char *arduino_path = "/dev/ttyACM0";
int serial_port;
struct termios tty;
void init_serial(){
//do cereal things https://blog.mbedded.ninja/programming/operating-systems/linux/linux-serial-ports-using-c-cpp/
serial_port = open(arduino_path, O_RDWR | O_NOCTTY | O_NDELAY);
if (serial_port < 0) {
ROS_ERROR("Error %i from open: %s", errno, strerror(errno));
}
memset(&tty, 0, sizeof tty);
if(tcgetattr(serial_port, &tty) != 0) {
printf("Error %i from tcgetattr: %s\n", errno, strerror(errno));
}
//set flags
tty.c_cflag &= ~PARENB;
tty.c_cflag |= CS8; // 8 bits per byte (most common)
tty.c_cflag &= ~CRTSCTS;
tty.c_cflag |= CREAD | CLOCAL;
tty.c_lflag &= ~ICANON;
tty.c_lflag &= ~ECHO; // Disable echo
tty.c_lflag &= ~ECHOE; // Disable erasure
tty.c_lflag &= ~ECHONL; // Disable new-line echo
tty.c_lflag &= ~ISIG;
tty.c_iflag &= ~(IXON | IXOFF | IXANY);
tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL);
tty.c_oflag &= ~OPOST; // Prevent special interpretation of output bytes (e.g. newline chars)
tty.c_oflag &= ~ONLCR; // Prevent conversion of newline to carriage return/line feed
tty.c_cc[VTIME] = 10; // Wait for up to 1s (10 deciseconds), returning as soon as any data is received.
tty.c_cc[VMIN] = 0;
cfsetispeed(&tty, B9600);
cfsetospeed(&tty, B9600);
if (tcsetattr(serial_port, TCSANOW, &tty) != 0) {
printf("Error %i from tcsetattr: %s\n", errno, strerror(errno));
}
}
std::string read_port(){
// Allocate memory for read buffer, set size according to your needs
char read_buf [256];
memset(&read_buf, '\0', sizeof(read_buf));
int n = read(serial_port, &read_buf, sizeof(read_buf));
std::string ret(read_buf);
return ret;
}
int main(int argc, char **argv){
ros::init(argc, argv, "sensor_handler");
ros::NodeHandle n;
init_serial();
while(ros::ok()){
cout << read_port() << std::endl;
}
}
Arduino code:
bool startup;
//Soil pins
const int soil_sensor_A0_AI = 0;
const int soil_sensor_A0_P = 0;
const int soil_sensor_A1_AI = 1;
const int soil_sensor_A1_P = 1;
const int soil_sensor_B0_AI = 2;
const int soil_sensor_B0_P = 2;
const int soil_sensor_B1_AI = 3;
const int soil_sensor_B1_P = 3;
int no_soil_sensors = 4;
//timer for the water
double water_timer;
int hours_delay = 4;
//water level vars
int water_level_sensor_pin = 5; //must be a PWM pin
int water_level; //in mm^3
double min_water = 20;
void setup() {
Serial.begin(9600);
//Setup soil moisture power pins as outputs
pinMode(soil_sensor_A0_P, OUTPUT);
pinMode(soil_sensor_A1_P, OUTPUT);
pinMode(soil_sensor_B0_P, OUTPUT);
pinMode(soil_sensor_B1_P, OUTPUT);
pinMode(water_level_sensor_pin, INPUT);
//init timer
water_timer = micros();
startup = true;
}
void loop() {
//check if starting up
if(startup){
check_water();
check_soil();
startup = false;
water_timer = micros();
}
/*
* if last check+delay in micros is less than or equal to current time then it means it is time to run a soil check.
*/
if(water_timer + (3600000000*hours_delay) <= micros() ){
check_water();
check_soil();
water_timer = micros();
}
//keep checking water, good way to monitor for leaks
check_water();
}
void check_soil() {
Serial.print("$SOIL:");
if(water_level < min_water){
Serial.println("E, Water level is too low to water the plants");
return;
}
for(int i = 0; i<no_soil_sensors; i++){
switch(i){
case soil_sensor_A0_AI:
digitalWrite(soil_sensor_A0_P, HIGH);
Serial.print("A0,");
Serial.print(analogRead(soil_sensor_A0_AI));
Serial.print(";");
digitalWrite(soil_sensor_A0_P, LOW);
break;
case soil_sensor_A1_AI:
digitalWrite(soil_sensor_A1_P, HIGH);
Serial.print("A1,");
Serial.print(analogRead(soil_sensor_A1_AI));
Serial.print(";");
digitalWrite(soil_sensor_A1_P, LOW);
break;
case soil_sensor_B0_AI:
digitalWrite(soil_sensor_B0_P, HIGH);
Serial.print("B0,");
Serial.print(analogRead(soil_sensor_B0_AI));
Serial.print(";");
digitalWrite(soil_sensor_B0_P, LOW);
break;
case soil_sensor_B1_AI:
digitalWrite(soil_sensor_B1_P, HIGH);
Serial.print("B1,");
Serial.print(analogRead(soil_sensor_B1_AI));
Serial.print(";");
digitalWrite(soil_sensor_B1_P, LOW);
break;
default:
Serial.println("E, SOIL_SENSORS");
break;
}
}
Serial.println("");
}
void check_water(){
//I don't know the math behind this yet but it will be in here
Serial.print("$WATER:");
double water_voltage = digitalRead(water_level_sensor_pin);
//math
double water_level = 0;
Serial.print(water_level);
if(water_level <= min_water){
Serial.print(";E, Water Level Low");
}
Serial.println("");
}