README.rst
1.. zephyr:code-sample:: usb-cdc-acm
2 :name: USB CDC-ACM
3 :relevant-api: usbd_api _usb_device_core_api
4
5 Use USB CDC-ACM driver to implement a serial port echo.
6
7Overview
8********
9
10This sample app demonstrates use of a USB Communication Device Class (CDC)
11Abstract Control Model (ACM) driver provided by the Zephyr project.
12Received data from the serial port is echoed back to the same port
13provided by this driver.
14This sample can be found under :zephyr_file:`samples/subsys/usb/cdc_acm` in the
15Zephyr project tree.
16
17Requirements
18************
19
20This project requires an USB device driver, which is available for multiple
21boards supported in Zephyr.
22
23Building and Running
24********************
25
26Reel Board
27===========
28
29To see the console output of the app, open a serial port emulator and
30attach it to the USB to TTL Serial cable. Build and flash the project:
31
32.. zephyr-app-commands::
33 :zephyr-app: samples/subsys/usb/cdc_acm
34 :board: reel_board
35 :goals: flash
36 :compact:
37
38Running
39=======
40
41Plug the board into a host device, for example, a PC running Linux.
42The board will be detected as shown by the Linux dmesg command:
43
44.. code-block:: console
45
46 usb 9-1: new full-speed USB device number 112 using uhci_hcd
47 usb 9-1: New USB device found, idVendor=8086, idProduct=f8a1
48 usb 9-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
49 usb 9-1: Product: CDC-ACM
50 usb 9-1: Manufacturer: Intel
51 usb 9-1: SerialNumber: 00.01
52 cdc_acm 9-1:1.0: ttyACM1: USB ACM device
53
54The app prints on serial output (UART1), used for the console:
55
56.. code-block:: console
57
58 Wait for DTR
59
60Open a serial port emulator, for example minicom
61and attach it to detected CDC ACM device:
62
63.. code-block:: console
64
65 minicom --device /dev/ttyACM1
66
67The app should respond on serial output with:
68
69.. code-block:: console
70
71 DTR set, start test
72 Baudrate detected: 115200
73
74And on ttyACM device, provided by zephyr USB device stack:
75
76.. code-block:: console
77
78 Send characters to the UART device
79 Characters read:
80
81The characters entered in serial port emulator will be echoed back.
82
83Troubleshooting
84===============
85
86If the ModemManager runs on your operating system, it will try
87to access the CDC ACM device and maybe you can see several characters
88including "AT" on the terminal attached to the CDC ACM device.
89You can add or extend the udev rule for your board to inform
90ModemManager to skip the CDC ACM device.
91For this example, it would look like this:
92
93.. code-block:: none
94
95 ATTRS{idVendor}=="8086" ATTRS{idProduct}=="f8a1", ENV{ID_MM_DEVICE_IGNORE}="1"
96
97You can use
98``/lib/udev/rules.d/77-mm-usb-device-blacklist.rules`` as reference.
99
