Running Multiple USB CDC ACM ports simultaneously

[narangmayank]

Is it possible to emulate COM 4 ports over nRF USB using CDC ACM device class? I was able to get 3 working but when I added 4th one it didn't worked out. Is there any

limitation in the hardware or software side for the same?

My dts overlay looks like,

/ {
chosen {
zephyr,console = &cdc_acm_uart0;
};
};

&zephyr_udc0 {
cdc_acm_uart0: cdc_acm_uart0 {
compatible = "zephyr,cdc-acm-uart";
label = "CDC_ACM_0";
};

cdc_acm_uart1: cdc_acm_uart1 {
compatible = "zephyr,cdc-acm-uart";
label = "CDC_ACM_1";
};

cdc_acm_uart2: cdc_acm_uart2 {
compatible = "zephyr,cdc-acm-uart";
label = "CDC_ACM_2";
};

cdc_acm_uart3: cdc_acm_uart3 {
compatible = "zephyr,cdc-acm-uart";
label = "CDC_ACM_3";
};
};

As soon as I added the definition of cdc_acm_uart3 in the overlay, it just stop working. No COM Port is visible.

 

SoC: nRF52840

OS: Windows 11

Platform: NCS v2.8.0

This is based on zephyr cdc acm example which you can find github.com/.../cdc_acm

Thanks in Advance!

[Kenneth]

Hello,

I havent tried it, but if you enable:

CONFIG_LOG=y

CONFIG_LOG_MODE_IMMEDIATE=y

CONFIG_RESET_ON_FATAL_ERROR=n

There is no error or fault?

Kenneth

[narangmayank]

Hi Kenneth 

This doesn't help. Are you aware of any such limitations of emulating multiple COM ports?

I'm using following usb conf,

CONFIG_STDOUT_CONSOLE=y

CONFIG_USB_DEVICE_STACK=y

CONFIG_USB_DEVICE_PRODUCT="Zephyr CDC ACM sample"

CONFIG_USB_DEVICE_PID=0x0001

# CONFIG_USB_DRIVER_LOG_LEVEL_ERR=y

# CONFIG_USB_DEVICE_LOG_LEVEL_ERR=y

CONFIG_SERIAL=y

CONFIG_CONSOLE=y

CONFIG_USB_CDC_ACM=y

CONFIG_UART_INTERRUPT_DRIVEN=y

CONFIG_UART_LINE_CTRL=y

CONFIG_USB_DEVICE_INITIALIZE_AT_BOOT=y

Regards,

Mayank

[narangmayank]

I changed back the console to uart, got this error output which says failed to enable usb, I think thats why I'm not able to see any COM port.

*** Booting nRF Connect SDK v2.8.0-a2386bfc8401 ***
*** Using Zephyr OS v3.7.99-0bc3393fb112 ***
[00:00:00.363,525] <inf> cdc_acm_echo: Starting App...
[00:00:00.363,586] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,586] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,586] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,616] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,616] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,616] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,647] <err> usb_nrfx: invalid endpoint index/address
[00:00:00.363,647] <err> usb_descriptor: Failed to validate endpoints
[00:00:00.363,647] <err> usb_descriptor: Failed to fixup USB descriptor
[00:00:00.363,647] <err> usb_device: Failed to configure USB device stack
[00:00:00.363,677] <err> cdc_acm_echo: Failed to enable USB

[Kenneth]

The hardware only have a limited number of endpoints available, but I would expect it could support more than 3, is there any other USB class than CDC?

Kenneth

[narangmayank]

I'm not sure about other USB class but CDM ACM require 2 IN endpoints per instance. So max we can have is 3 only. I'm closing this ticket since I got the answer, Thanks!