CO2 Gas Measurement Demo

The ADuCM360_demo_cn0338 is a CO2 gas measurement demo project for the EVAL-ADICUP360 base board with additional EVAL-CN0338-ARDZ shield, created using the GNU ARM Eclipse Plug-ins in Eclipse environment.

General description

This project is a good example for how to use EVAL-ADICUP360 board in different combinations with shield boards. It expand the list of possible applications that can be done with the base board.

The ADuCM360_demo_cn0338 project uses the EVAL-CN0338-ARDZ shield which is a complete thermopile-based gas sensor using the nondispersive infrared (NDIR) principle.

https://media.githubusercontent.com/media/analogdevicesinc/system-level/main/docs/solutions/reference-designs/eval-adicup360/images/cn0338_hw_combined.png

The CN0338 circuit uses 24-bit, Σ-Δ ADCs of the ADuCM360 microcontroller for simultaneous sampling of a dual element thermopile at programmable rates of 3.5 Hz to 3.906 kHz.

https://media.githubusercontent.com/media/analogdevicesinc/system-level/main/docs/solutions/reference-designs/eval-adicup360/images/cn0338_demo_21.png

The ADuCM360_demo_cn0338 application perform ADC reads, processes them and make all necessary calculations in order to provide gas concentration. Beside this it provide an interactive command line interpreter which offer the possibility to the user to customize his CN0338 shield. The UART interface (1 start bit, 8-bits data length, no parity bits and 2 stop bits) is used to send(and to receive) data to (from) a terminal window. Default value of UART baud rate is 115200 Hz, but you have the possibility to change it at run time from command line.

To start the application you need first to press ENTER key (CR) from the keyboard. A welcome message will pop-up, after that you can type ‘help’ to find out which are the available commands.

The project offers two calibration techniques based on Beer-Lambert Law. Find which one is more closer to your application (see Calibration Procedure).

Note

When you will want to use for a first time CN0338 shield, please be aware that all environment variables are set to default and the CN0338 requires calibaration.

You can check current values of the system variables using ‘printsettings’ command and also have the possibility to reset system variables to default values - ‘resetTodefault’.

Note

The UART baud rate can be reset to default value using terminal command or pressing RESET button from EVAL-ADICUP360 board.

To start CN0338 measurements use ‘run’ command. This one will display CO2 concentration; temperature; low, high and diff voltage values for REF (peak-to-peak output of the reference detector), ACT (peak-to-peak output of the active detector) and FA (fractional absorbance).

From command line you can set following parameters: ADC sample frequency; serial port baud rate; falling and rising edge time for NDIR signal; NDIR light source frequency.

Note

To abort any running command you need to use ‘Ctrl + c’ key combination.

Calibration procedure

The CN0338 need to be calibrated before first use to archive best performance. There have two calibrate algorithm in CN0338 firmware, customer can choice one of algorithm to apply in calibrate procedure. The two algorithm is: Beer-Lambert Law and Modified Beer-Lambert Law, for more details about those two algorithm, please reference the circuit note in www.analog.com/cn0338.

Beer-Lambert Law calibrate procedure

  • input the command: sbllcalibrate

  • Inject low concentration or zero gas (nitrogen) to the chamber, please maker sure the gas is full filling with chamber.

  • wait for gas evenly dispersion

  • input the low concentration gas’s concentration in terminal

  • Inject high concentration CO2 to the chamber, please maker sure the gas is full filling with chamber.

  • wait for gas evenly dispersion

  • input the high concentration gas’s concentration in terminal

  • wait for the system to complete the calibration

Modified Beer-Lambert Law calibrate procedure

  • input the command: mbllcalibrate

  • input the constant parameter b

  • input the constant parameter c

  • Inject low concentration or zero gas (nitrogen) to the chamber, please maker sure the gas is full filling with chamber.

  • wait for gas evenly dispersion

  • input the low concentration gas’s concentration in terminal

  • Inject high concentration CO2 to the chamber, please maker sure the gas is full filling with chamber.

  • wait for gas evenly dispersion

  • input the high concentration gas’s concentration in terminal

  • wait for the system to complete the calibration

After above calibrate procedure the CN0338 is ready to use.

Demo Requirements

The following is a list of items needed in order to replicate this demo.

  • Hardware

    • EVAL-ADICUP360

    • EVAL-CN0338-ARDZ

    • 7V to 12V DC Power Supply

    • Mirco USB to USB cable

    • PC or Laptop with a USB port

  • Software

    • ADuCM360_demo_cn0338 software

    • CrossCore Embedded Studio (2.7.0 or higher)

    • ADuCM36x DFP (1.0.2 or higher)

    • CMSIS ARM Pack (4.3.0 or higher)

    • Serial Terminal Program

      • Such as Putty or Tera Term

Setting up the hardware

  • To program the base board, set the jumpers/switches as shown in the next figure. The important jumpers/switches are highlighted in red.

https://media.githubusercontent.com/media/analogdevicesinc/system-level/main/docs/solutions/reference-designs/eval-adicup360/images/cn0337_demo_3.png

  • Connect the EVAL-CN0338-ARDZ to the Arduino connectors P2, P3, P5, P6, P7, P8, P9 of the EVAL-ADICUP360 board.

  • Plug in the DC Power supply into the DC barrel jack (P11) on the EVAL-ADICUP360.

  • Plug in the USB cable from the PC to the EVAL-ADICUP360 base board via the Debug USB.(P14)

Obtaining the Source Code

There are two basic ways to program the ADICUP360 with the software for the CN0338.

  • Dragging and Dropping the .Bin to the MBED drive

  • Building, Compiling, and Debugging using CCES

Using the drag and drop method, the software is going to be a version that Analog Devices creates for testing and evaluation purposes. This is the EASIEST way to get started with the reference design.

Importing the project into CrossCore is going to allow you to change parameters and customize the software to fit your needs, but will be a bit more advanced and will require you to download the CrossCore toolchain.

The software for the ADuCM360_demo_cn0338 demo can be found here:

Download

Prebuilt CN0338 Bin File

Complete CN0338 Source Files

Note

For more information on importing, debugging, or other tools related questions, please see the tools user guide.

Configuring the Software Parameters

  • Thermopile output data processing algorithm - ALGORITHM_PEAK2PEAK for peak-to-peak algorithm or ALGORITHM_AVERAGE for averaging algorithm(ADC.h).

#define ALGORITHM_PEAK2PEAK

  • If the ALGORITHM_AVERAGE is defined, the system will use the average value of all ADC sample point in half IR chop period as the input.

  • If the ALGORITHM_PEAK2PEAK is defined, the system will use the maximum value of all ADC sample point in IR high period and minimum value of all ADC sample point in IR low period as the input.

Outputting Data

Serial Terminal Output

  • In order to view the data, you must flash the program to the EVAL-ADICUP360.

  • Once complete you will need to switch the USB cable from the DEBUG USB (P14) to the USER USB (P13).

  • Then follow the UART settings below with the serial terminal program.

Following is the UART configuration.

Select COM Port
Baud rate: 115200
Data: 8 bit
Parity: none
Start: 1 bit
Stop: 2 bit
Flow Control: none

  • The user must press the <ENTER> key to get the welcome message for this demo.

  • The user then must type in the word <help> to bring up the application menu.

  • The application must be calibrated before accurate reading can be taken. There are two calibration modes that you can choose from, and each one has a set of calibration steps required. Please see the Calibration Procedure section on what to do for the calibration.

  • Once the calibration is complete, type <run> into the console window to get your results.

https://media.githubusercontent.com/media/analogdevicesinc/system-level/main/docs/solutions/reference-designs/eval-adicup360/images/cn0338_demo_21.png

How to use the Tools

The official tool we promote for use with the EVAL-ADICUP360 is CrossCore Embedded Studio. For more information on downloading the tools and a quick start guide on how to use the tool basics, please check out the Tools Overview page.

Importing

For more detailed instructions on importing this application/demo example into the CrossCore Embedded Studios tools, please view our How to import existing projects into your workspace section.

Debugging

For more detailed instructions on importing this application/demo example into the CrossCore Embedded Studios tools, please view our How to configure the debug session section.

Project structure

The ADuCM360_demo_cn0338 is a C++ project that uses ADuCM36x C/C++ Project structure.

This project contains: system initialization part - disabling watchdog, setting system clock, enabling clock for peripherals; port configuration for ADC, UART via P0.1/P0.2; UART read/write functions; Memory read/write functions; NDIR calculations; C02 concentration and temperature conversions.

https://media.githubusercontent.com/media/analogdevicesinc/system-level/main/docs/solutions/reference-designs/eval-adicup360/images/cn0338_demo_4.png

In the src and include folders you will find the source and header files related to CN0338 software application. The Communication.cpp/h files contain UART specific data, meanwhile the CN0338.cpp/h files contain the calculation part, the ADC.cpp/h files contain ADC channels handling and Flash.cpp/h provide memory management. The entire ‘command line interpreter’ is summarize in Cmd.cpp/h, Cmd_settings.cpp/h and Cmd_calibrate.cpp/h files. Because most of the parameters can be set at run time, not need to configure so much values before you start application.

The RTE folder contains device and system related files:

  • Device Folder – contains low levels drivers for ADuCM360 microcontroller.(try not to edit these files)

  • system.rteconfig - Allows the user to select the peripherial components they need, along with the startup and ARM cmsis files needed for the project.