USB HID CDC ACM Application¶
This sample app demonstrates use of multiple USB classes with multiple instances. It combines two HID instances and two CDC ACM instances. This sample can be found under samples/subsys/usb/hid-cdc in the Zephyr project tree.
This project requires an USB device driver and multiple endpoints.
The board hardware must have a push button connected via a GPIO pin. These are called “User buttons” on many of Zephyr’s Supported Boards.
Unsupported board: sw0 devicetree alias is not defined
You may see additional build errors if the
sw0 alias exists, but is not
If the devicetree aliases
sw3 are defined, they will
also be used as additional buttons as described below.
Building and Running¶
This sample can be built for multiple boards. To build and flash it for the nRF52840 DK board:
west build -b nrf52840dk_nrf52840 samples/subsys/usb/hid-cdc west flash
After you have built and flashed the sample app image to your board, plug the board into a host device, for example, a PC running Linux. Two CDC ACM interfaces (for example /dev/ttyACM1 and /dev/ttyACM2) and two HID devices will be detected:
usb 2-2: new full-speed USB device number 3 using ohci-pci usb 2-2: New USB device found, idVendor=2fe3, idProduct=0003, bcdDevice= 2.03 usb 2-2: New USB device strings: Mfr=1, Product=2, SerialNumber=3 usb 2-2: Product: Zephyr HID and CDC ACM sample usb 2-2: Manufacturer: ZEPHYR usb 2-2: SerialNumber: 86FE679A598AC47A cdc_acm 2-2:1.0: ttyACM1: USB ACM device input: ZEPHYR Zephyr HID and CDC ACM sample as /devices/pci0000:00/0000:00:06.0/usb2/2-2/2-2:1.2/0003:2FE3:0100.0002/input/input8 hid-generic 0003:2FE3:0100.0002: input,hidraw1: USB HID v1.10 Mouse [ZEPHYR Zephyr HID and CDC ACM sample] on usb-0000:00:06.0-2/input2 cdc_acm 2-2:1.3: ttyACM2: USB ACM device input: ZEPHYR Zephyr HID and CDC ACM sample as /devices/pci0000:00/0000:00:06.0/usb2/2-2/2-2:1.5/0003:2FE3:0100.0003/input/input9 hid-generic 0003:2FE3:0100.0003: input,hidraw2: USB HID v1.10 Keyboard [ZEPHYR Zephyr HID and CDC ACM sample] on usb-0000:00:06.0-2/input5
You can now connect to both CDC ACM ports:
minicom -D /dev/ttyACM1 -b 115200
minicom -D /dev/ttyACM2 -b 115200
After both ports have been connected to, messages explaining usage of each port will be displayed:
Welcome to CDC_ACM_0 Supported commands: up - moves the mouse up down - moves the mouse down right - moves the mouse to right left - moves the mouse to left
Welcome to CDC_ACM_1 Enter a string and terminate it with ENTER. It will be sent via HID when BUTTON 2 is pressed. You can modify it by sending a new one here.
CDC ACM 0 may be used to control the mouse by typing a command and pressing ENTER.
CDC ACM 1 is used to control the keyboard - any string typed into it and finished with ENTER will be saved on the device and typed back to the host when BUTTON 2 is pressed.
Buttons have following functions:
Button 0 moves HID mouse in random direction
Button 1 is a left HID mouse button
Button 2 types the string sent with CDC ACM 1 using HID keyboard
Button 3 is a CAPS LOCK on HID keyboard