99 lines
2.6 KiB
ReStructuredText
99 lines
2.6 KiB
ReStructuredText
.. zephyr:code-sample:: usb-cdc-acm
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:name: USB CDC-ACM
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:relevant-api: usbd_api _usb_device_core_api uart_interface
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Use USB CDC-ACM driver to implement a serial port echo.
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Overview
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********
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This sample app demonstrates use of a USB Communication Device Class (CDC)
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Abstract Control Model (ACM) driver provided by the Zephyr project.
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Received data from the serial port is echoed back to the same port
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provided by this driver.
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This sample can be found under :zephyr_file:`samples/subsys/usb/cdc_acm` in the
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Zephyr project tree.
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Requirements
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************
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This project requires an USB device driver, which is available for multiple
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boards supported in Zephyr.
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Building and Running
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********************
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Reel Board
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===========
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To see the console output of the app, open a serial port emulator and
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attach it to the USB to TTL Serial cable. Build and flash the project:
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.. zephyr-app-commands::
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:zephyr-app: samples/subsys/usb/cdc_acm
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:board: reel_board
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:goals: flash
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:compact:
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Running
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=======
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Plug the board into a host device, for example, a PC running Linux.
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The board will be detected as shown by the Linux dmesg command:
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.. code-block:: console
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usb 9-1: new full-speed USB device number 112 using uhci_hcd
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usb 9-1: New USB device found, idVendor=8086, idProduct=f8a1
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usb 9-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
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usb 9-1: Product: CDC-ACM
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usb 9-1: Manufacturer: Intel
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usb 9-1: SerialNumber: 00.01
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cdc_acm 9-1:1.0: ttyACM1: USB ACM device
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The app prints on serial output (UART1), used for the console:
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.. code-block:: console
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Wait for DTR
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Open a serial port emulator, for example minicom
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and attach it to detected CDC ACM device:
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.. code-block:: console
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minicom --device /dev/ttyACM1
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The app should respond on serial output with:
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.. code-block:: console
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DTR set, start test
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Baudrate detected: 115200
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And on ttyACM device, provided by zephyr USB device stack:
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.. code-block:: console
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Send characters to the UART device
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Characters read:
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The characters entered in serial port emulator will be echoed back.
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Troubleshooting
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===============
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If the ModemManager runs on your operating system, it will try
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to access the CDC ACM device and maybe you can see several characters
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including "AT" on the terminal attached to the CDC ACM device.
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You can add or extend the udev rule for your board to inform
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ModemManager to skip the CDC ACM device.
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For this example, it would look like this:
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.. code-block:: none
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ATTRS{idVendor}=="8086" ATTRS{idProduct}=="f8a1", ENV{ID_MM_DEVICE_IGNORE}="1"
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You can use
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``/lib/udev/rules.d/77-mm-usb-device-blacklist.rules`` as reference.
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