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This version (20 Jul 2022 07:13) was approved by Mahesh Phalke.The Previously approved version (23 Jul 2021 12:42) is available.Diff

AD7124 Temperature Measurement Demo Example

This page gives an overview of using the 'ARM Mbed' platform supported temperature measurement firmware example with Analog Devices AD7124 Evaluation board and SDP-K1 controller board (or any other Mbed supported target board). The firmware example is console based, which provides an user-interactive menu options for user to select and configure the multiple temperature sensors at different instances, such as 2/3/4-wire RTDs, NTC Thermistors and Thermocouples.

The connection block diagram is described below:

This code has been developed and tested on SDP-K1 Controller Board using the on-board Arduino/SDP-120 Headers. However, same code can be used without or with little modifications on any other Mbed supported board which has Arduino Header Support on it, such as STM32-Discovery, STM32-Nucleo, etc.

Hardware Connections

Connect the VIO_ADJUST jumper on the SDP-K1 board to 3.3V position to drive SDP-K1 GPIOs at 3.3V.

For AD7124 evaluation board connections and jumper settings, refer the respective evaluation board manual. Arduino connector is used as default interface type for both the boards in the software.

SDP-K1 is powered through USB connection from the computer. SDP-K1 acts as a serial device when connected to PC, which creates a COM Port to connect to serial terminal (console based application) running on windows-os. The COM port assigned to a device can be seen through the device manager for windows based OS.


Software Downloads

Latest firmware (Use below link):

Quick Start to use AD7124 Mbed Firmware

If you have some familiarity with the Mbed platform, the following is a basic list of steps required to start running the code:

  • Connect the AD7124 EVAL-board to the SDP-K1 controller board as specified in hardware connections section.
  • Connect the SDP-K1 controller board to your computer over USB provided along with SDP-K1 board.
  • Import the code into Keil Studio from above firmware download link by using “File→Import Project…” option. Specify the web link of code in URL and check 'Make this the active project’ option.

  • Make sure all dependent libraries are obtained correctly by IDE.

  • Compile the code as shown below. After a successful compile a binary will be downloaded to your computer - store this into your computer. Drag and drop (or copy) this binary file to the SDP-K1 USB drive mounted in your computer file system (similar to C/D drives) to flash firmware into MCU.


Using the Firmware

Configure your serial terminal ( Tera Term) for below settings:

The AD7124 temperature measurement example main menu looks like below (with Tera Term):

The firmware is designed to be intuitive to use, and requires little explanation, simply enter a number corresponding to the required command and follow the on-screen prompts.

Firmware allows user to perform the measurement for single or multiple (more than one) temperature sensors of same type. Below sensors are supported:

  1. Single or Multiple 2/3/4-wire RTDs (default is PT100)
  2. Single Or Multiple Thermocouple (default is T-type)
  3. Single Or Multiple Thermistors (default is 10K NTC)

User must ensure all sensors are connected to AD7124 evaluation board as per configurations specific in the software and on this wiki page (see subsequent sections). If user intend to change these configurations in the software, the hardware connections must be modified as per new configurations. The details about altering the software modules for modifying the configurations are given in 'Modifying Firmware' section.

In order to use analog inputs AIN4 and AIN5 on Legacy AD7124 Eval board (with SDP-120 interface only) in any of the demo mode, make sure to route the sensor connections directly through LK6 link, instead of physical screw-terminal connector. Make sure LK6 link is removed for the same purpose.

Multiple RTD (2/3/4-wire Configurations)

Multiple 2-wire RTD configurations:

Multiple 3-wire RTD configurations:

Multiple 4-wire RTD configurations:


Multiple Thermocouple Configurations

Cold Junction Compensation (CJC) configurations for TC measurement:


Multiple NTC Thermistor Configurations

Calibrating 3-wire RTDs

Firmware provides an option for user to perform calibrated measurement on 3-wire RTD sensors. There are two types of calibration options available in the firmware. User must modify sensor hardware connections according to configuration defined in the software. Based on selected calibration type, the sensors are first calibrated and then 3-wire RTD measurement is performed on them. For more information on the calibration scheme, refer the design note on RTD measurement.

Calibration is allowed to perform only on Multiple RTD sensors and not on a single RTD sensor.

Calibrating ADC (Internal and System Calibration)

Firmware allows user to perform ADC calibration on the current sensor configuration (demo mode) selected through console menu. ADC calibration helps to remove any offset Or gain error present on the input channels. The updated device coefficients (gain and offset) post ADC calibration are used/applied during the sensor measurement. Therefore, once calibration is complete, user must go to the previous demo mode which was selected before ADC calibration and then perform the measurement on selected sensors. The calibration coefficients (gain and offset) are applied only on the analog input channels which were enabled prior to calibration. Also after calibration if any new demo mode is selected apart from the one which was enabled during calibration, the calibration coefficients are reset and doesn't applied on input channels. In this case, user must perform the calibration again.

Internal ADC calibration is straightforward but system calibration needs user inputs (typically after applying full-scale/zero-scale) voltages on selected analog inputs.


Modifying Firmware

app_config.h

This file can be used to:

  1. Select the 'Active Device' as either AD7124-4 Or AD7124-8. Default active device is AD7124-4.
  2. Select the SDP_K1 interface type as either Arduino Or SDP-120. Default is Arduino.

ad7124_regs_configs.h

This file defines the analog inputs, excitation sources, PGA, reference sources and power mode for all sensor demo mode configurations.

ad7124_regs_config_rtd.c, ad7124_regs_config_thermistor.c, ad7124_regs_config_thermocouple.c

These files define the AD7124 register configurations used for various sensor demo modes.

ad7124_user_config.c

This file defines the user configurations for the AD7124, such as SPI parameters (frequency, mode, etc) and other init parameters used by No-OS drivers to initialize AD7124 device. These are the parameters loaded into device when device is powered-up or power-cycled.

ad7124_console_app.c

This file defines the functionality for selecting and displaying sensor configurations (hardcoded in the software), perform ADC sampling on selected sensor channels and display temperature measurement result for selected sensors.

ad7124_temperature_sensor.cpp

This file defines the functions which acts as wrapper for calling 'tempsensor' library functions to calculate the temperature based on resistance or voltages. The fixed sensors such as NTC 10K, T type thermocouple, PT100/PT1000 RTD are used.

No-OS Drivers for AD7124

No-OS drivers provide the high level abstracted layer for digital interface of AD7124 device. The complete digital interface (to access memory map and perform data read) is done in integration with low level platform drivers.

The functionality related with No-OS drivers is covered in below 2 files:

  1. ad7124.c
  2. ad7124.h
It is hoped that the most common functions of the AD7124 are coded, but it's likely that some special functionality is not implemented. Feel free to consult Analog Devices Engineer-Zone for feature requests, feedback, bug-reports etc.
resources/tools-software/product-support-software/ad7124_temperature_measurement_demo.txt · Last modified: 20 Jul 2022 07:12 by Mahesh Phalke