This code example demonstrates the use of opamp as a buffer along with 12-bit SAR ADC on EZ-PD™ PMG1-S3 MCU. The opamp is configured to act as a buffer between external signals and input channels of a 12-bit SAR ADC to provide impedance matching for high-impedance signals. The measured signal is then printed on the UART terminal.
Provide feedback on this code example.
- ModusToolbox™ v3.0 or later (tested with v3.0)
- Board support package (BSP) minimum required version: 3.0.0
- Programming language: C
- Associated parts: EZ-PD™ PMG1-S3 MCU
- GNU Arm® Embedded Compiler v10.3.1 (
GCC_ARM) - Default value ofTOOLCHAIN - Arm® Compiler v6.16 (
ARM) - IAR C/C++ Compiler v9.30.1 (
IAR)
- EZ-PD™ PMG1-S3 Prototyping Kit (
PMG1-CY7113) – Default value ofTARGET
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Connect the board to your PC using a USB cable through the KitProg3 USB connector (J1). This cable is used for programming the EZ-PD™ PMG1 device and can be used during debugging. In addition, it transfers the UART data from the serial port to the PC to display it on a serial monitor.
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Connect the USB PD port (J10) to a USB-C power adapter/USB port on the PC using a Type-C/Type-A to Type-C cable to power the EZ-PD™ PMG1 device for normal operations.
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For EZ-PD™ PMG1-S3 kits of revision 3 or lower, connect the UART Tx (J6.10), and UART Rx (J6.9) lines from the EZ-PD™ EZ-PD™ PMG1 kit to J3.8 and J3.10 on KitProg3 respectively to establish a UART connection between the KitProg3 and the EZ-PD™ PMG1 device. Kits with a higher revision have UART lines internally connected and therefore, external wiring is not required.
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Configure the CTBm 0 block as a Follower to work in a buffer mode as shown in Figure 1.
Figure 1. Opamp in Follower configuration
a. Connect the voltage signal to be buffered to opamp Vplus (P3.0).
Note: Used variable DC power supply to provide input voltage in this example.
- ADC is configured as unsigned single-ended. opamp output and ADC pins are connected through AMUXBUS, therefore, no need for an external connection. See the 12-bit ADC configuration.
See the kit user guide for details on configuring the board.
Install a terminal emulator to display the serial data. Instructions in this document use Tera Term.
Create the project and open it using one of the following:
In Eclipse IDE for ModusToolbox™
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Click the New Application link in the Quick Panel (or, use File > New > ModusToolbox™ Application). This launches the Project Creator tool.
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Pick a kit supported by the code example from the list shown in the Project Creator – Choose Board Support Package (BSP) dialog.
When you select a supported kit, the example is reconfigured automatically to work with the kit. To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can use the Library Manager to select or update the BSP and firmware libraries used in this application. To access the Library Manager, click the link from the Quick Panel.
You can also just start the application creation process again and select a different kit.
If you want to use the application 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.
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In the Project Creator - Select Application dialog, choose the example by enabling the checkbox.
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(Optional) Change the suggested New Application Name.
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The Application(s) Root Path defaults to the Eclipse workspace which is usually the desired location for the application. If you want to store the application in a different location, you can change the Application(s) Root Path value. Applications that share libraries must be in the same root path.
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Click Create to complete the application creation process.
For more details, see the Eclipse IDE for ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mt_ide_user_guide.pdf).
In command-line interface (CLI)
ModusToolbox™ provides the Project Creator as both a GUI tool and the command-line tool (project-creator-cli). The 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 "project-creator-cli" tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--board-id |
Defined in the <id> field of the BSP manifest |
Required |
--app-id |
Defined in the <id> 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 |
The following example clones the "mtb-example-pmg1-opamp-buffer-saradc" application with the desired name "MyOpampBufferSarADC" configured for the PMG1-CY7113 BSP into the specified working directory, C:/mtb_projects:
project-creator-cli --board-id PMG1-CY7113 --app-id mtb-example-pmg1-opamp-buffer-saradc --user-app-name MyOpampBufferSarADC --target-dir "C:/mtb_projects"
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™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
To work with a different supported kit later, use the Library Manager to choose the BSP for the supported kit. You can invoke the Library Manager GUI tool from the terminal by using the make library-manager command or use the Library Manager CLI tool (library-manager-cli) to change the BSP.
The "library-manager-cli" tool has the following arguments:
| Argument | Description | Required/optional |
|---|---|---|
--add-bsp-name |
Name of the BSP that should be added to the application | Required |
--set-active-bsp |
Name of the BSP that should be as active BSP for the application | Required |
--add-bsp-version |
Specify the version of the BSP that should be added to the application if you do not wish to use the latest from manifest | Optional |
--add-bsp-location |
Specify the location of the BSP (local/shared) if you prefer to add the BSP in a shared path | Optional |
The following example adds the PMG1-CY7113 BSP to the already created application and makes it the active BSP for the app:
~/ModusToolbox/tools_3.0/library-manager/library-manager-cli --project "C:/mtb_projects/MyOpampBufferSarADC" --add-bsp-name PMG1-CY7113 --add-bsp-version "latest-v3.X" --add-bsp-location "local"
~/ModusToolbox/tools_3.0/library-manager/library-manager-cli --project "C:/mtb_projects/MyOpampBufferSarADC" --set-active-bsp APP_PMG1-CY7113
In third-party IDEs
Use one of the following options:
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Use the standalone Project Creator tool:
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Launch Project Creator from the Windows Start menu or from {ModusToolbox™ install directory}/tools_{version}/project-creator/project-creator.exe.
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In the initial Choose Board Support Package screen, select the BSP, and click Next.
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In the Select Application screen, select the appropriate IDE from the Target IDE drop-down menu.
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Click Create and follow the instructions printed in the bottom pane to import or open the exported project in the respective IDE.
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Use command-line interface (CLI):
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Follow the instructions from the In command-line interface (CLI) section to create the application.
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Export the application to a supported IDE using the
make <ide>command. -
Follow the instructions displayed in the terminal to create or import the application as an IDE project.
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For a list of supported IDEs and more details, see the "Exporting to IDEs" section of the ModusToolbox™ user guide (locally available at {ModusToolbox™ install directory}/docs_{version}/mtb_user_guide.pdf).
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Ensure that the steps listed in the Hardware setup section are complete.
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Ensure that the jumper shunt on the power selection jumper (J5) is placed at positions 2-3 to enable programming mode.
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Connect the board to your PC using the USB cable through the KitProg3 USB connector (J1). This cable is used for programming the EZ-PD™ PMG1 device.
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Program the board using one of the following:
Using Eclipse IDE for ModusToolbox™
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Select the application project in the Project Explorer.
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In the Quick Panel, scroll down, and click <Application Name> Program (KitProg3_MiniProg4).
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_ARMNote: This application supports only PMG1-CY7113 BSP.
-
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After programming the kit, disconnect the USB cable and change the position on the power selection jumper (J5) to 1-2 to power the kit through the USB PD port in operational mode.
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Reconnect the USB cable to the KitProg3 Type-C port (J1).
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Open a terminal program and select the KitProg3 COM port. Set the serial port parameters to 8N1 and 115200 baud.
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Power the kit through the USB PD port (J10), using the second USB cable.
As soon as the kit is powered through the USB PD port (J10), the User LED(LED3) starts blinking and the application starts printing "12-bit SAR ADC with OpAmp as buffer". Consequently, the digital output codes and the corresponding value of the measured analog input voltages are automatically displayed at an interval of 500 milliseconds each.
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Voltage in Vout (P5.2) pin is the buffered output (1x) of Vplus (P3.0). Use a multimeter to measure the voltage in Vplus (P3.0) and compare it with the corresponding voltages and digital codes displayed on the serial terminal using the standard ADC conversion formula:
Code = (Vin/Vref) * (2^n - 1), where 'n' is the resolution in the number of bits used for representing the digital code.
Figure 2. UART terminal display of code
Note: Enable DEBUG_PRINT macro for UART print.
You can debug the example to step through the code. In the 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.
Ensure that the board is connected to your PC using the USB cables through both the KitProg3 USB connector and the USB PD port, with the jumper shunt on the power selection jumper (J5) placed at positions 1-2.
This code example uses PASS 0 CTB 0 OpAmp 1 under PASS 0 Continuous Time Block Mini (CTBm) 0, a 12-bit SAR ADC provided in the programmable analog block, available only on EZ-PD™ PMG1-S3 devices. Both opamp and ADC can be configured using the Device Configurator tool in ModusToolbox™.
CTBm 0 block is configured as Follower and has one input (Vplus Input) and one output (Output (to pin)). Input and output pins can be routed as external pins using firmware-controlled switches used for analog routing.
Detailed configuration of PASS 0 CTB 0 OpAmp1 parameters such as input, output pin selection, and output drive using Device Configurator:
-
Select the application project in the Project Explorer.
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In the Quick Panel, scroll down to the Tools section, and click Device Configurator.
Figure 3. PASS 0 CTB 0 OpAmp 1 configuration using Device Configurator
(a) Select Output Drive as Output to pin to route the opamp output externally to the pin and internally to the ADC.
(b) For opamp input and output, configure the Vplus Input pin to P3.0 and Output (to pin) to P5.2 and PASS 0 12-bit SAR ADC 0 vplus (SARADC0).
PASS0 SARADC0 has three inputs: Vplus, Vminus, and ext_vref. The inputs can be routed to the required external pins using a set of firmware-controlled switches used for analog routing.
PASS 0 12-bit SAR ADC 0 has been configured as single-ended mode. Single-ended input modes are preferred for reading analog direct current (DC) signals. In addition to this, the output code can be displayed in both signed and unsigned formats.
Detailed configuration of PASS 0 12-bit SAR ADC 0 for parameters such as reference voltage, resolution, number of channels, scan rate, channel acquisition time, clock frequency, input mode, result format, interrupts, and so on are included in the Device Configurator tool.
Figure 4. PASS 0 12-bit SAR ADC 0 configuration using Device Configurator
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On the Device Configurator, select PASS 0 12-bit SAR ADC 0 under Programmable Analog (PASS) 0 in the Peripherals tab. Do the following changes to ADC configuration fields:
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In the Channel 0 section, select input modes as 'Single-ended'.
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Under the Sampling section, select the output result formats as 'Unsigned'.
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Change other parameters to modify the performance of ADC according to the application requirements.
Note: If you make any changes on the Device Configurator, save the changes and then re-program the kit to activate the new configuration.
Some of the important parameters that are responsible for the performance of PASS 0 12-bit SAR ADC 0 are listed as follows:
(a) Set Vref Select to Vdda.
(b) Set the ADC Clock Frequency to 1.778 MHz.
(c) Set Samples Averaged to 256 to minimize the effect of noise and other errors. This results in averaging out 256 samples from a particular channel in a single scan to generate the final ADC output code value.
(d) Enable Averaging under Channel 0 for the sample averaging.
(e) Ch0 Vplus is ADC pin configuration, here select opamp Vout Pin (P5.2) as a Ch0 Vplus input to inter-connect the Vout and Ch0 Vplus using AMUXBUSA/B to avoid external wiring.
(f) Select Full Resolution 12-bit to ensure maximum performance of the ADC.
For single-ended unsigned configuration, code 0 corresponds to the Vplus input at 0 V. Similarly, code 2047 corresponds to the Vplus input equal to Vref (3.3 V).
Note that the maximum voltage swing across Vplus and Vneg pin that the ADC can read is equal to Vref.
It implies that | Vplus - Vneg | <= Vref
View the CTBm 0 and PASS 0 12-bit SAR ADC 0 internal signal routing by using the Analog Routing tab in the Device Configurator.
Figure 5. Analog routing in Device Configurator
Figure 6. Firmware flowchart
Note: This ADC configuration results in a sample conversion delay of 2.304 milliseconds (scan duration) after triggering. This time interval can be effectively utilized to run codes to perform some user-defined tasks. However, a delay of 500 milliseconds has been allotted between each ADC sample display to slow down the UART terminal display rate for better visibility.
-
EZ-PD™ PMG1 MCU: Customize the 12-bit SAR ADC with opamp as buffer application functionality through the compile-time parameter that can be turned ON/OFF through the main.c file.
| Macro name | Description | Allowed values |
|---|---|---|
DEBUG_PRINT |
Debug print macro to enable the UART print | 1u to enable 0u to disable |
Table 1. Application resources
| Resource | Alias/object | Purpose |
|---|---|---|
| Programmable Analog (PASS) 0 | SARADC0 | Uses 12-bit SAR ADC to convert analog input voltage to digital codes |
| PASS 0 Continuous Time Block Mini (CTBm) 0 | CYBSP_CTB0_OPAMP1 | Uses CTB 0 to work as opamp Follower |
| SCB 4 | CYBSP_UART | Uses UART SCB 4 block for serial communication to send ADC code values through a serial port |
| LED (BSP) | CYBSP_USER_LED | User LED to indicate the output |
| Resources | Links |
|---|---|
| Application notes | AN232553 – Getting started with EZ-PD™ PMG1 MCU on ModusToolbox™ software AN232565 – EZ-PD™ PMG1 MCU hardware design guidelines and checklist |
| Code examples | Using ModusToolbox™ on GitHub |
| Device documentation | EZ-PD™ PMG1 MCU datasheets |
| Development kits | Select your kits from the Evaluation board finder. |
| Libraries on GitHub | mtb-pdl-cat2 – Peripheral Driver Library (PDL) |
| Tools | Eclipse IDE for ModusToolbox™ – ModusToolbox™ is a collection of easy-to-use software and tools enabling rapid development with Infineon MCUs, covering applications from embedded sense and control to wireless and cloud-connected systems using AIROC™ Wi-Fi and Bluetooth® connectivity devices. |
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: CE238349 – EZ-PD™ PMG1 MCU: 12-bit SAR ADC with opamp as buffer
| Version | Description of change |
|---|---|
| 1.0.0 | New code example |
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