co2 sensor garbage characters on serial monitor

[regeier]

I am trying to get the grove c02 sensor working. The sensor is plugged in to port D2 on the grove expansion board on a seeeduino. I copied and pasted the example code given for the sensor but on the serial monitor I just get garbage characters output, but no temperature or co2ppm.

Can this sensor be plugged into D2 or is there anything that needs to be changed with the following configuration ?

#include <SoftwareSerial.h>
SoftwareSerial s_serial(2, 3); // TX, RX

[seeed techsupport team]

Hi there,

please refer to viewtopic.php?f=16&t=7754&p=26798&hilit ... CO2#p26798. thanks.

[regeier]

I fixed the code from that post and uploaded it, but still get garbage characters out.

Code: Select all

#include <SoftwareSerial.h>
const int pinRx = 9;
const int pinTx = 8;

SoftwareSerial s_serial(pinTx,pinRx);
#define sensor s_serial

unsigned char flg_get = 0; // if get sensor data

const unsigned char cmd_get_sensor[] =
{
    0xff, 0x01, 0x86, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x79
};

void setup()
{
  Serial.begin(115200);
  sensor.begin(9600);
}

bool sendCmdGetDta(int *gas_strength, int *temperature)
{
  for(int i=0; i<sizeof(cmd_get_sensor); i++)
  {
    sensor.write(cmd_get_sensor[i]);
  }

long cnt_timeout = 0;
while(!sensor.available()) // wait for data
{
  delay(1);
  cnt_timeout++;

  if(cnt_timeout>1000)return 0; // time out
}

int len = 0;
unsigned char dta[20];

while(sensor.available())
  {
    dta[len++] = sensor.read();
  }

  if((9 == len) && (0xff == dta[0]) && (0x86 == dta[1])) // data ok
  {
    *gas_strength = 256*dta[2]+dta[3];
    *temperature = dta[4] - 40;
    return 1;
  }
  return 0;
}

void loop()
{
  flg_get = 0;
  int gas, temp;

  if(sendCmdGetDta(&gas, &temp)) // get data ok
  {
    Serial.println("get data ok: ");
    Serial.print("gas_strength = ");
    Serial.println(gas);
    Serial.print("\ttemperature = ");
    Serial.println(temp);
  }
  else
  {
    Serial.println("get data error");
  }
  delay(1000);
}

void serialEvent()
{
while (Serial.available())
  {
    char c = Serial.read();
    if(c == 'g')flg_get = 1;
  }
}

[seeed techsupport team]

Hi there,

please post a picture about the hardware connection. we can follow your hardware connection to simulate the issue. thanks.

[regeier]

co2.jpeg (118.77 KiB) Viewed 2969 times

[regeier]

Were you able to repeat the problem ?

[bill.yu]

Hi there,

I can not repeat the issue. So please try below method to confirm if the hardware is good. thanks.

1. hardware connection, connect the co2 module to usb to ttl module., gng->gnd, Vcc-->5v, tx->rx, rx->tx.


2. use the serial monitor tool to monitor the output


3. you can calculate the co2 ppm by High*256+Low

thanks.

[regeier]

Thanks for helping with this. I have now found the problem and fixed it. The sensor is working.

The baud rate on the serial monitor did not match the baud rate set at the arduino end. Once they were set the same the output is correct.

[u1080665]

This code works very well. The one posted on the website did not work for me. There must be an error with it. Can you guys look into it?

I fixed the code from that post and uploaded it, but still get garbage characters out.

Code: Select all

#include <SoftwareSerial.h>
const int pinRx = 9;
const int pinTx = 8;

SoftwareSerial s_serial(pinTx,pinRx);
#define sensor s_serial

unsigned char flg_get = 0; // if get sensor data

const unsigned char cmd_get_sensor[] =
{
    0xff, 0x01, 0x86, 0x00, 0x00,
    0x00, 0x00, 0x00, 0x79
};

void setup()
{
  Serial.begin(115200);
  sensor.begin(9600);
}

bool sendCmdGetDta(int *gas_strength, int *temperature)
{
  for(int i=0; i<sizeof(cmd_get_sensor); i++)
  {
    sensor.write(cmd_get_sensor[i]);
  }

long cnt_timeout = 0;
while(!sensor.available()) // wait for data
{
  delay(1);
  cnt_timeout++;

  if(cnt_timeout>1000)return 0; // time out
}

int len = 0;
unsigned char dta[20];

while(sensor.available())
  {
    dta[len++] = sensor.read();
  }

  if((9 == len) && (0xff == dta[0]) && (0x86 == dta[1])) // data ok
  {
    *gas_strength = 256*dta[2]+dta[3];
    *temperature = dta[4] - 40;
    return 1;
  }
  return 0;
}

void loop()
{
  flg_get = 0;
  int gas, temp;

  if(sendCmdGetDta(&gas, &temp)) // get data ok
  {
    Serial.println("get data ok: ");
    Serial.print("gas_strength = ");
    Serial.println(gas);
    Serial.print("\ttemperature = ");
    Serial.println(temp);
  }
  else
  {
    Serial.println("get data error");
  }
  delay(1000);
}

void serialEvent()
{
while (Serial.available())
  {
    char c = Serial.read();
    if(c == 'g')flg_get = 1;
  }
}

[u1080665]

This code just save my day.
Thank you Regeier.

u1080665