USB CDC Echo Sample App

Description

The USB CDC Echo Sample application demonstrates USB CDC communication and echo functionality on the supported boards for this application. It performs comprehensive USB CDC testing including serial port communication, message transmission, and echo response validation to ensure reliable bidirectional USB data transfer.

The sample includes multiple USB CDC operations:

USB CDC initialization: Initialize USB CDC serial communication with host PC.
Serial port interface: Establish command-line interface for serial communication.
Message transmission: Send test messages over USB CDC connection.
Echo response: Receive and validate echoed responses from connected device.
Communication testing: Perform basic USB CDC communication validation.
Data integrity: Ensure message integrity during transmission and reception.

During each run, the app logs initialization status, communication progress, message transmission results, and echo validation outcomes. This makes it easy for end users to confirm that USB CDC setup and echo operations are working as expected.

The latest example structure uses a common application source tree with board-specific hardware setup kept under hw/<BOARD>/. For this app:

Common application sources such as main.c and USB CDC-related files stay in the app root.
Application defconfigs are stored under configs/.
Board and hardware-specific setup is selected from hw/<BOARD>/, for example hw/SR110_RDK/.

The application can also be exported and built as a standalone app repository. In that flow, keep this app in its own directory, point SRSDK_DIR to the SDK root, and build from the app directory itself. For the full application workflow model, see Astra MCU SDK User Guide.

Supported Boards

This application supports:

SR110_RDK

Select the defconfig that matches your target board, and the build system will pick the corresponding board-specific hardware setup from hw/<BOARD>/.

Prerequisites

Choose one setup path:
- CLI: Setup and Install SDK using CLI
- VS Code: Setup and Install SDK using VS Code
Install required Python package for serial_sender.py:
- pyserial

pip install pyserial

Test Case Selection

Before building, choose the testcase defconfig that matches your target board.

You can:

Select the required defconfig directly from the application’s configs/ directory.
Run make list_defconfigs from the application directory to list all supported defconfigs.

Available defconfigs:

sr110_rdk_cm55_usb_cdc_echo_sample_app_defconfig

Building and Flashing the Example using VS Code

Use the VS Code flow described in the SR110 guide and the VS Code Extension guide:

Build (VS Code):

Open Build and Deploy -> Build Configurations.
Select the usb_cdc_echo_sample_app project configuration in the Project Configuration dropdown.
Build with Build (SDK+Project) for the first build, or Build (Project) for rebuilds.

Flash (VS Code):

Use Image Conversion to generate the flash image.
Use Image Flashing (SWD/JTAG) to flash the firmware image.

Building and Flashing the Example using CLI

Use the CLI flow described in the SR110 guide:

SR110 Build and Flash with CLI

Build (CLI):

Build from the application directory itself:

cd <sdk-root>/examples/usb_examples/usb_cdc_echo_sample_app
export SRSDK_DIR=<sdk-root>
make <app_defconfig> BUILD=SRSDK

For faster rebuilds when only app code changes, reuse the app-local installed SDK package:

cd <sdk-root>/examples/usb_examples/usb_cdc_echo_sample_app
export SRSDK_DIR=<sdk-root>
make build

If this app has been exported to its own repository, use the same commands from that exported app directory after setting SRSDK_DIR to the SDK root.

Flash (CLI):

Activate the SDK venv (required for image generation tools):

# Linux/macOS
source <sdk-root>/.venv/bin/activate
# Windows PowerShell
.\.venv\Scripts\Activate.ps1

Generate the flash image:

cd <sdk-root>/tools/srsdk_image_generator
python srsdk_image_generator.py \
  -B0 \
  -flash_image \
  -sdk_secured \
  -spk "<sdk-root>/tools/srsdk_image_generator/Inputs/spk_rc4_1_0_secure_otpk.bin" \
  -apbl "<sdk-root>/tools/srsdk_image_generator/Inputs/sr100_b0_bootloader_ver_0x012F_ASIC.axf" \
  -m55_image "<sdk-root>/examples/usb_examples/usb_cdc_echo_sample_app/out/sr110_cm55_fw/release/sr110_cm55_fw.elf" \
  -flash_type "GD25LE128" \
  -flash_freq "67"

Flash the firmware image:

cd <sdk-root>
python tools/openocd/scripts/flash_xspi_tcl.py \
  --cfg_path tools/openocd/configs/sr110_m55.cfg \
  --image tools/srsdk_image_generator/Output/B0_Flash/B0_flash_full_image_GD25LE128_67Mhz_secured.bin \
  --erase-all

Running the Application using VS Code Extension

Connect a USB cable to the application USB port on the SR110 board and press RESET.
For logging output, click SERIAL MONITOR and connect to the DAP logger port on J14.
- To make it easier to identify, ensure only J14 is plugged in (not J13).
- The logger port is not guaranteed to be consistent across OSes. As a starting point:
  - Windows: try the lower-numbered J14 COM port first.
  - Linux/macOS: try the higher-numbered J14 port first.
- If you do not see logs after a reset, switch to the other J14 port.
On Windows, if required, update the COM port driver in Device Manager to USB Serial Device.

Run the sender script:

python serial_sender.py -c <COM_PORT> -b <BAUD_RATE> -m "<MESSAGE_TO_SEND>"

Expected Logs

Serial Monitor Logs

---- Opened the serial port COM60 ----
0391470271:[0][WRN][LOGR]:Changing logger interface to LOGGER_IF_UART_1
0000000156:[0][INF][SYS ]:Application drivers initialization complete without errors.
0000004348:[0][INF][SYS ]:------------------------------------------
0000007710:[0][INF][SYS ]:            Hello  ASTRA                  
0000011076:[0][INF][SYS ]:------------------------------------------
0000014439:[0][INF][SYS ]:System initialization done
0000017035:[0][INF][SYS ]:sr110 SDK version 1.3.0
0000019526:[0][INF][USB ]:USB device unmounted
0000021858:[0][DBG][HAPI]:------------------------------------------
0000025220:[0][DBG][HAPI]:       Host API Router task               
0000028578:[0][DBG][HAPI]:------------------------------------------
0000031944:[0][INF][HAPI]:Active interface is USB
0000034404:[0][INF][USB ]:Usb CDC Echo Test Task Enter
0000037098:[0][INF][GENR]:Usecase manager service started.
0000039987:[0][DBG][HAPI]:A new service was registered, service ID: 6.
0000321147:[0][INF][USB ]:USB device mounted

Terminal Logs

PS C:\Release_1.3.0\Astra_MCU_SDK1.3.0\examples\SR110_RDK\usb_examples\usb_cdc_echo_sample_app> python .\serial_sender.py -c COM4 -b 230400 -m "Hello ASTRA!!"
Connected to COM4 at 230400 baud.
Sent: 'Hello ASTRA!!'
Response: HELLO ASTRA!!

Features of Python Script

Customizable Serial Port: Select COM port/device path.
Adjustable Baud Rate: Configure baud rate as required.
Send Custom Messages: Send custom payloads with CRLF.
Read Responses: Read back response data from device.
Error Handling: Prints useful errors for common serial issues.