Connecting CO2 sensor using USB

Using Arduino Sensors
1

I've got to interface an AlphaSense CO2 sensor (manual included as attachment) with an Uno using USB. I'm stuck and can't seem to find any examples or information on the internet. Does anybody have any experience with this? Does arduino even support doing this type of thing?

The AlphaSense CO2 sensor is connected to a software serial port on the Uno using a FTDI TTL 232R 5V cable, the same one used for the mini. Using an oscilloscope I confirmed that a signal was being sent out but couldn't find anything coming in. I double then triple checked the connections, still nothing.

I'm pretty sure the port settings are correct since I first connected with Matlab then copied those settings into my sketch.

Here is my sketch

#include <SoftwareSerial.h>
SoftwareSerial AlphaSense(3, 4); // RX, TX

void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);
  while (!Serial) {
    // wait for serial port to connect
  }

  AlphaSense.begin(19200);
}

void loop() {
  // put your main code here, to run repeatedly:
  AlphaSense.print("N");   //N for concentration, T for temperature, V for lamp voltage
  AlphaSense.print('\r');   //Carriage return 
  delay(20);

  char ppm[10];
  int i = 0;
  while (AlphaSense.available()) {
    Serial.println(AlphaSense.read());
    i++;
  }

  Serial.println(ppm);
  delay(500);
}

Here is my Matlab code

s=serial('COM41')           %setting port
set(s,'BaudRate',19200);    %setting baud rate to 19200
set(s,'Terminator','CR')    %setting terminator to CR / ASCII 13 / '\r'

fprintf(s,'N')  %asking for CO2 concentration
fgetl(s)        %recieving input data

Is there anything I should try to fix this problem?

072-0150 NDIR IRC-A Transmitter manual draft 4.pdf (473 KB)

2

Does arduino even support doing this type of thing?

Probably not.

I'd guess that the USB isn't sending RS232 and it's the driver installed on your PC that is doing some fancy stuff to give an easy com port interface. USB to Arduino usually involves a USB host shield, but these are set up with firmaware for a particular device, not just any USB gizmo.

3

I don't remember installing a driver but I guess Matlab could be doing something behind the scenes.

I've found some shields that implement USB 2.0 standard, the same standard the sensor runs on. Would these work?

4

You'd need to know the device class/protocol being used by your sensor, and that sort of information isn't often supplied by the manufacturer.

A decent generic host shield will support loads of device classes, but it's up to you to take the risk and buy one. I've never used USB directly with Arduino, so I'm getting out of my depth here.