This example demonstrates how PSoC® 6 MCU detects a USB suspend condition, enters a low-power state, and restores normal operation when USB activity resumes.
PSoC 6 MCU operates in the CPU active power mode before the host decides to suspend the USB device. The PSoC 6 MCU device goes to deep sleep as soon as a suspend condition is detected so that it consumes less power. The USB device maximum suspend current should not exceed 500 µA (for a low-power device) to be compliant with the USB specification. When the host decides to wake up the USB device, it drives a resume condition on the bus. This drives the PSoC 6 MCU device to wake up and change its power mode to CPU active.
The example uses an LED to indicate the USB device state as well as the PSoC 6 MCU power mode. The LED is OFF when a suspend condition is detected and PSoC 6 MCU is in deep sleep. The LED is ON when the USB is active and PSoC 6 MCU is in CPU active power mode.
To see the USB descriptor, use the usbdev-configurator tool located at <ModusToolbox_install_dir>/tools_<version>/usbdev-configurator. In the tool, open the design.cyusbdev file located under the /COMPONENT_CUSTOM_DESIGN_MODUS/TARGET_<BSP> folder.
Provide feedback on this Code Example.
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Note: This code example version requires ModusToolbox software version 2.2 or later and is not backward compatible with v2.1 or older versions.
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Board Support Package (BSP) minimum required version: 2.0.0
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Programming Language: C
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Associated Parts: All PSoC® 6 MCU parts
- GNU Arm® Embedded Compiler v9.3.1 (
GCC_ARM) - Default value ofTOOLCHAIN - Arm compiler v6.11 (
ARM) - IAR C/C++ compiler v8.42.2 (
IAR)
- PSoC 6 Wi-Fi BT Prototyping Kit (
CY8CPROTO-062-4343W) - Default value ofTARGET - PSoC 6 WiFi-BT Pioneer Kit (
CY8CKIT-062-WIFI-BT) - PSoC 62S2 Wi-Fi BT Pioneer Kit (
CY8CKIT-062S2-43012) - PSoC 62S1 Wi-Fi BT Pioneer Kit (
CYW9P62S1-43438EVB-01) - PSoC 62S1 Wi-Fi BT Pioneer Kit (
CYW9P62S1-43012EVB-01) - PSoC 62S3 Wi-Fi BT Prototyping Kit (
CY8CPROTO-062S3-4343W) - PSoC 64 Secure Boot Wi-Fi BT Pioneer Kit (
CY8CKIT-064B0S2-4343W)
This example uses the board's default configuration. See the kit user guide to ensure that the board is configured correctly.
Note: The PSoC 6 BLE Pioneer Kit (CY8CKIT-062-BLE) and the PSoC 6 WiFi-BT Pioneer Kit (CY8CKIT-062-WIFI-BT) ship with KitProg2 installed. The ModusToolbox software requires KitProg3. Before using this code example, make sure that the board is upgraded to KitProg3. The tool and instructions are available in the Firmware Loader GitHub repository. If you do not upgrade, you will see an error like "unable to find CMSIS-DAP device" or "KitProg firmware is out of date".
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.
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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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Optionally, change the suggested New Application Name.
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Enter the local path in the Application(s) Root Path field to indicate where the application needs to be created.
Applications that can share libraries can be placed 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}/ide_{version}/docs/mt_ide_user_guide.pdf).
ModusToolbox provides the Project Creator as both a GUI tool and a command line tool to easily create one or more ModusToolbox applications. See the "Project Creator Tools" section of the ModusToolbox User Guide for more details.
Alternatively, you can manually create the application using the following steps:
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Download and unzip this repository onto your local machine, or clone the repository.
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Open a CLI terminal and navigate to the application folder.
On Linux and macOS, you can use any terminal application. On Windows, open the modus-shell app from the Start menu.
Note: The cloned application contains a default BSP file (TARGET_xxx.mtb) in the deps folder. Use the Library Manager (
make modlibscommand) to select and download a different BSP file, if required. If the selected kit does not have the required resources or is not supported, the application may not work. -
Import the required libraries by executing the
make getlibscommand.
Various CLI tools include a -h option that prints help information to the terminal screen about that tool. For more details, see the ModusToolbox User Guide (locally available at {ModusToolbox install directory}/docs_{version}/mtb_user_guide.pdf).
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Follow the instructions from the CLI section to create the application, and import the libraries using the
make getlibscommand. -
Export the application to a supported IDE using the
make <ide>command.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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Follow the instructions displayed in the terminal to create or import the application as an IDE project.
If using a PSoC 64 Secure MCU kit (like CY8CKIT-064B0S2-4343W, CY8CPROTO-064B0S3), the PSoC 64 Secure MCU must be provisioned with keys and policies before being programmed. Follow the instructions in the Secure Boot SDK User Guide to provision the device. If the kit is already provisioned, copy-paste the keys and policy folder to the application folder.
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Connect the board to your PC using the provided USB cable through the KitProg3 USB connector.
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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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Program the board.
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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).
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Using CLI:
From the terminal, execute the
make programcommand to build and program the application using the default toolchain to the default target. You can specify a target and toolchain manually:make program TARGET=<BSP> TOOLCHAIN=<toolchain>Example:
make program TARGET=CY8CPROTO-062-4343W TOOLCHAIN=GCC_ARM
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Connect another USB cable (or reuse the same cable used to program the kit) to the USB device connector.
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In the PC, verify that a new USB device enumerates as a Virtual COM port.
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Run any terminal emulator and make a new connection to the Virtual COM port. Observe the message “USB is active” periodically printed in the terminal. Observe that the kit LED is ON.
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To put the device into suspend mode, on a Windows PC, go to the Start menu and put the PC into sleep mode. This makes the USB traffic stop; PSoC 6 MCU enters the suspend mode, and the LED turns OFF.
Note: When putting the PC in sleep, the board should be powered either by connecting KitProg3 connector to another PC or power source.
Note: If the USB Host cable is disconnected, while keeping the board powered through the kitprog connector, the device goes to deep-sleep.
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Use the mouse or keyboard to wake up the PC. The host generates a resume condition on the USB; PSoC 6 MCU resumes and restores communication through USB (the device is not enumerated again). Observe that the LED in the kit is ON again.
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After the PC wakes up, the communication with the USBFS device can be observed as described in Step 5.
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 more 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 of main(). 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 of main(). See KBA231071 to learn about this and for the workaround.
In the main firmware routine, the USBFS block is configured to use the Communication Device Class (CDC). After enumeration, the device periodically checks for activity every 1 ms. The USB device is suspended if there is no activity on the bus for longer than 3 ms. Normally, Start-Of-Frame (SOF) packets are sent by the host every 1 ms. The USBFS driver layer is not capable of tracking the suspend condition by itself. Therefore, a timer is placed in the design to provide ticks each 1 ms. The USB activity is checked every tick to identify when bus is idle for 3 ms.
After the USB suspend condition is detected, PSoC 6 MCU leaves the CPU active power mode and goes to deep sleep. This allows the device to reduce power consumption while the host does not communicate with it. Before going to deep sleep, the LED is turned OFF, the timer is disabled, and the wakeup source interrupt is enabled. The wakeup source is the falling edge on the USB Dp pin. The Cy_USBFS_Dev_Drv_Suspend() function is also called to prepare the USB hardware block to enter suspend mode.
When the host wants to wake the device up after the suspend condition, it does so by reversing the polarity of the signal on the data lines for at least 20 ms. The signal is completed with the low-speed end of the packet signal. As soon as the Dp pin polarity is reverted, PSoC 6 MCU wakes up because a wakeup event occurs (falling edge on the Dp pin). The USBFS hardware block configuration is restored by calling the Cy_USBFS_Dev_Drv_Resume() function. The timer is re-enabled, the LED is turned ON, and the wakeup source interrupt is disabled.
Table 1. Application Resources
| Resource | Alias/Object | Purpose |
|---|---|---|
| USBDEV (PDL) | CYBSP_USBDEV | USB Device configured with CDC Class descriptor |
| TIMER (HAL) | timer_obj | Used for generating interrupts at interval of 1ms |
| GPIO (HAL) | CYBSP_USER_LED | User LED |
| Application Notes | |
|---|---|
| AN228571 – Getting Started with PSoC 6 MCU on ModusToolbox | Describes PSoC 6 MCU devices and how to build your first application with ModusToolbox |
| AN221774 – Getting Started with PSoC 6 MCU on PSoC Creator | Describes PSoC 6 MCU devices and how to build your first application with PSoC Creator |
| AN210781 – Getting Started with PSoC 6 MCU with Bluetooth Low Energy (BLE) Connectivity on PSoC Creator | Describes PSoC 6 MCU with BLE Connectivity devices and how to build your first application with PSoC Creator |
| AN215656 – PSoC 6 MCU: Dual-CPU System Design | Describes the dual-CPU architecture in PSoC 6 MCU, and shows how to build a simple dual-CPU design |
| Code Examples | |
| Using ModusToolbox | Using PSoC Creator |
| Device Documentation | |
| PSoC 6 MCU Datasheets | PSoC 6 Technical Reference Manuals |
| Development Kits | Buy at www.cypress.com |
| CY8CKIT-062-BLE PSoC 6 BLE Pioneer Kit | CY8CKIT-062-WiFi-BT PSoC 6 WiFi-BT Pioneer Kit |
| CY8CPROTO-063-BLE PSoC 6 BLE Prototyping Kit | CY8CPROTO-062-4343W PSoC 6 Wi-Fi BT Prototyping Kit |
| CY8CKIT-062S2-43012 PSoC 62S2 Wi-Fi BT Pioneer Kit | CY8CPROTO-062S3-4343W PSoC 62S3 Wi-Fi BT Prototyping Kit |
| CYW9P62S1-43438EVB-01 PSoC 62S1 Wi-Fi BT Pioneer Kit | CYW9P62S1-43012EVB-01 PSoC 62S1 Wi-Fi BT Pioneer Kit |
| CY8CKIT-064B0S2-4343W PSoC 64 Secure Boot Wi-Fi BT Pioneer Kit | CY8CPROTO-064B0S3 PSoC 64 Secure Boot Prototyping Kit |
| Libraries | |
| PSoC 6 Peripheral Driver Library (PDL) and docs | mtb-pdl-cat1 on GitHub |
| Cypress Hardware Abstraction Layer (HAL) Library and docs | mtb-hal-cat1 on GitHub |
| Retarget-IO - A utility library to retarget the standard input/output (STDIO) messages to a UART port | retarget-io on GitHub |
| Middleware | |
| CapSense® library and docs | capsense on GitHub |
| Links to all PSoC 6 MCU Middleware | psoc6-middleware on GitHub |
| Tools | |
| Eclipse IDE for ModusToolbox | The cross-platform, Eclipse-based IDE for IoT designers that supports application configuration and development targeting converged MCU and wireless systems. |
| PSoC Creator™ | The Cypress IDE for PSoC and FM0+ MCU development. |
Cypress provides a wealth of data at www.cypress.com to help you select the right device, and quickly and effectively integrate it into your design.
For PSoC 6 MCU devices, see How to Design with PSoC 6 MCU - KBA223067 in the Cypress community.
Document Title: CE223305 - PSoC 6 MCU: USB Suspend and Resume
| Version | Description of Change |
|---|---|
| 1.0.0 | New code example |
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