This code example demonstrates low-power sensing of a thermistor and ambient light sensor (ALS) using the SAR ADC of the PSoC™ 6 MCU. This code example is supported only for devices that have an SAR ADC capable of operating in System Deep Sleep mode.
Sensor voltages are measured by the SAR ADC while the device is in System Deep Sleep mode resulting in a power-efficient solution.
In this code example, the temperature value in degree celsius and ambient light in percentage are displayed on the UART terminal every half second.
Provide feedback on this code example.
- ModusToolbox™ v3.1 or later (tested with v3.1)
- Board support package (BSP) minimum required version: 4.0.0
- Programming language: C
- Associated parts: All PSoC™ 6 MCU parts
- GNU Arm® Embedded Compiler v11.3.1 (
GCC_ARM) – Default value ofTOOLCHAIN - Arm® Compiler v6.16 (
ARM) - IAR C/C++ Compiler v9.30.1 (
IAR)
- PSoC™ 62S4 Pioneer Kit (
CY8CKIT-062S4) – Default value ofTARGET
This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly.
See the ModusToolbox™ tools package installation guide for information about installing and configuring the tools package.
Install a terminal emulator if you don't have one. Instructions in this document use Tera Term.
This example requires no additional software or tools.
The ModusToolbox™ tools package provides the Project Creator as both a GUI tool and a command line tool.
Use Project Creator GUI
-
Open the Project Creator GUI tool.
There are several ways to do this, including launching it from the dashboard or from inside the Eclipse IDE. For more details, see the Project Creator user guide (locally available at {ModusToolbox™ install directory}/tools_{version}/project-creator/docs/project-creator.pdf).
-
On the Choose Board Support Package (BSP) page, select a kit supported by this code example. See Supported kits.
Note: To use this code example for a kit not listed here, you may need to update the source files. If the kit does not have the required resources, the application may not work.
-
On the Select Application page:
a. Select the Applications(s) Root Path and the Target IDE.
Note: Depending on how you open the Project Creator tool, these fields may be pre-selected for you.
b. Select this code example from the list by enabling its check box.
Note: You can narrow the list of displayed examples by typing in the filter box.
c. (Optional) Change the suggested New Application Name and New BSP Name.
d. Click Create to complete the application creation process.
Use Project Creator CLI
The 'project-creator-cli' tool can be used to create applications from a CLI terminal or from within batch files or shell scripts. This tool is available in the {ModusToolbox™ install directory}/tools_{version}/project-creator/ directory.
Use a CLI terminal to invoke the 'project-creator-cli' tool. On Windows, use the command-line 'modus-shell' program provided in the ModusToolbox™ installation instead of a standard Windows command-line application. This shell provides access to all ModusToolbox™ tools. You can access it by typing "modus-shell" in the search box in the Windows menu. In Linux and macOS, you can use any terminal application.
The following example clones the "Low-power SAR ADC thermistor and ALS" application with the desired name "LowPowerSarAdcThermistorAls" configured for the CY8CKIT-062S4 BSP into the specified working directory, C:/mtb_projects:
project-creator-cli --board-id CY8CKIT-062S4 --app-id mtb-example-psoc6-low-power-sar-adc-thermistor-als --user-app-name LowPowerSarAdcThermistorAls --target-dir "C:/mtb_projects"
The 'project-creator-cli' tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--board-id |
Defined in the field of the BSP manifest | Required |
--app-id |
Defined in the field of the CE manifest | Required |
--target-dir |
Specify the directory in which the application is to be created if you prefer not to use the default current working directory | Optional |
--user-app-name |
Specify the name of the application if you prefer to have a name other than the example's default name | Optional |
Note: The project-creator-cli tool uses the
git cloneandmake getlibscommands to fetch the repository and import the required libraries. For details, see the "Project creator tools" section of the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
After the project has been created, you can open it in your preferred development environment.
Eclipse IDE
If you opened the Project Creator tool from the included Eclipse IDE, the project will open in Eclipse automatically.
For more details, see the Eclipse IDE for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_ide_user_guide.pdf).
Visual Studio (VS) Code
Launch VS Code manually, and then open the generated {project-name}.code-workspace file located in the project directory.
For more details, see the Visual Studio Code for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_vscode_user_guide.pdf).
Keil µVision
Double-click the generated {project-name}.cprj file to launch the Keil µVision IDE.
For more details, see the Keil µVision for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_uvision_user_guide.pdf).
IAR Embedded Workbench
Open IAR Embedded Workbench manually, and create a new project. Then select the generated {project-name}.ipcf file located in the project directory.
For more details, see the IAR Embedded Workbench for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_iar_user_guide.pdf).
Command line
If you prefer to use the CLI, open the appropriate terminal, and navigate to the project directory. On Windows, use the command-line 'modus-shell' program; on Linux and macOS, you can use any terminal application. From there, you can run various make commands.
For more details, see the ModusToolbox™ tools package user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
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Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
-
Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
-
Program the board using one of the following:
Using Eclipse IDE
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Select the application project in the Project Explorer.
-
In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).
In other IDEs
Follow the instructions in your preferred IDE.
Using CLI
From the terminal, execute the
make programcommand to build and program the application using the default toolchain to the default target. The default toolchain is specified in the application's Makefile but you can override this value manually:make program TOOLCHAIN=<toolchain>Example:
make program TOOLCHAIN=GCC_ARM -
-
After programming, the application starts automatically. Confirm that the sensor readings are displayed on the UART terminal as shown in Figure 1.
Figure 1. Sensor readings in terminal
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Touch the thermistor on the board and observe the change in the temperature readings on the terminal.
-
Block or increase the light over the ambient light sensor and observe the change in the percentage readings on the terminal.
-
Confirm that the user LED turns ON, when the light over the ambient light sensor is blocked.
You can debug the example to step through the code.
In Eclipse IDE
Use the <Application Name> Debug (KitProg3_MiniProg4) configuration in the Quick Panel. For details, see the "Program and debug" section in the Eclipse IDE for ModusToolbox™ user guide.
Note: (Only while debugging) On the CM4 CPU, some code in
main()may execute before the debugger halts at the beginning ofmain(). This means that some code executes twice – once before the debugger stops execution, and again after the debugger resets the program counter to the beginning ofmain(). See KBA231071 to learn about this and for the workaround.
In other IDEs
Follow the instructions in your preferred IDE.
The SAR ADC is configured with three channels - two differential channels for the thermistor and one single-ended channel for the ambient light sensor. The interface circuit and the resources used in the device are shown in Figure 2.
Figure 2. Sensor interface
This example demonstrates a low-power sensing solution using SAR ADC, which is configured to operate in System Deep Sleep mode. That is, while the CPU and other peripherals are turned OFF, the SAR ADC continues to scan the inputs and load the results into the FIFO. Scan is initiated by the timer configured to trigger the SAR ADC at a 400-Hz rate. The CPU wakes up only when the FIFO accumulates the configured number of samples, which in this case is after accumulating 120 samples from 40 scans (120 samples / 3 channels). With a timer period of 2.5 ms (1/400), the CPU is woken up every 100 ms (40 x 2.5 ms).
The CPU reads the FIFO data every 100 ms, and passes it through a first-order infinite impulse response (IIR) low-pass filter algorithm. The filtered values are used to calculate the temperature in degree celsius and ambient light intensity in percentage. The user LED is turned ON or OFF depending on the ambient light intensity value. The calculated values of temperature and ambient light intensity are also sent over the UART terminal every 500 ms.
Figure 3. Flowchart
Figure 4. Timing diagram and average current calculation
The current consumed by the PSoC™ 6 MCU device can be measured on the kit at the appropriate header. See the kit user guide for more details. The bench current measurement for different states of the firmware is shown in Table 1. Note that the thermistor circuit current is excluded from the readings. Current is calculated by setting the PSoC™ 6 MCU GPIO, driving the thermistor, to '0'. In addition, to get current readings for different states, certain modifications are made in the main.c code as shown in Table 1.
Table 1. Current measurement
| State | Average current |
|---|---|
| Analog resources configured but SAR ADC conversion is not started (timer is disabled). Device is put to System Deep Sleep mode | 8 µA |
| SAR ADC samples the input in System Deep Sleep mode every 2.5 ms, but FIFO interrupt is disabled which causes device to remain in System Deep Sleep mode | 52 µA |
| Normal operation - FIFO interrupt is enabled which causes device to wake up periodically every 100 ms to process the ADC data and transfer the result over UART every 500 ms | 74 µA |
Figure 5. Captured current waveform
This code example uses the custom configuration defined in the design.modus file located in the <application_folder>/templates/TARGET_<BSP-NAME>/config/design.modus folder. Important configurations are highlighted in Figures 6 to 12.
Figure 6. SAR common parameters for all channels
Figure 7. SAR channel parameters
Figure 8. SAR global parameters
Figure 9. FIFO parameters
Figure 10. AREF, Deep Sleep Clock, LPO and Timer parameters
Figure 11. Power parameters
Figure 12. Clock parameters
Table 2. Application resources
| Resource | Alias/object | Purpose |
|---|---|---|
| SAR (PDL) | SAR | SAR driver to measure sensor voltages |
| SYSANALOG (PDL) | PASS | SYSANALOG driver for AREF, timer and Deep Sleep clock configuration |
| UART (HAL) | cy_retarget_io_uart_obj | UART HAL object used by Retarget-IO for Debug UART port |
| GPIO (HAL) | CYBSP_USER_LED | User LED |
| Resources | Links |
|---|---|
| Application notes | AN228571 – Getting started with PSoC™ 6 MCU on ModusToolbox™ AN215656 – PSoC™ 6 MCU: Dual-CPU system design |
| Code examples | Using ModusToolbox™ on GitHub |
| Device documentation | PSoC™ 6 MCU datasheets PSoC™ 6 technical reference manuals |
| Development kits | Select your kits from the Evaluation board finder. |
| Libraries on GitHub | mtb-pdl-cat1 – PSoC™ 6 Peripheral Driver Library (PDL) mtb-hal-cat1 – Hardware Abstraction Layer (HAL) library retarget-io – Utility library to retarget STDIO messages to a UART port |
| Middleware on GitHub | psoc6-middleware – Links to all PSoC™ 6 MCU middleware |
| Tools | ModusToolbox™ – ModusToolbox™ software is a collection of easy-to-use libraries and tools enabling rapid development with Infineon MCUs for applications ranging from wireless and cloud-connected systems, edge AI/ML, embedded sense and control, to wired USB connectivity using PSoC™ Industrial/IoT MCUs, AIROC™ Wi-Fi and Bluetooth® connectivity devices, XMC™ Industrial MCUs, and EZ-USB™/EZ-PD™ wired connectivity controllers. ModusToolbox™ incorporates a comprehensive set of BSPs, HAL, libraries, configuration tools, and provides support for industry-standard IDEs to fast-track your embedded application development. |
Infineon provides a wealth of data at www.infineon.com to help you select the right device, and quickly and effectively integrate it into your design.
Document title: CE230699 - PSoC™ 6 MCU SAR ADC low-power sensing thermistor and ALS
| Version | Description of change |
|---|---|
| 1.0.0 | New code example |
| 2.0.0 | Updated code to support version v2.X of the CY8CKIT-062S4 BSP |
| 2.1.0 | Updated flowchart and timing diagram Updated the custom design file to use SAR personality v4.0 |
| 3.0.0 | Updated to support ModusToolbox™ v3.0 This version is not backward compatible with previous versions of ModusToolbox™ |
| 3.1.0 | Updated to support ModusToolbox™ v3.1 |
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