I have a USB CDC-ACM device emulating Serial over USB communication. The CDC Communications and Data interfaces are shown respectively on 2-1:1.0 (Comm) and 2-1:1.1 (Data) interface descriptors, and the cdc_acm driver is being loaded properly.
My issue is that only the Communication interface is being assigned to /dev/ttyACMX by cdc_acm driver, but the Data interface is ignored. It seems to prevents the device from working properly (a GBA ST2 Bill Validator using ccTalk protocol). It works fine on Windows 8+ using the usbser.sys driver.
With cdc_acm driver, dmesg and lsusb output is:
$ dmesg
[ 3484.982436] usb 2-1: new full-speed USB device number 4 using ohci-pci
[ 3485.251788] usb 2-1: New USB device found, idVendor=16f9, idProduct=0003
[ 3485.251792] usb 2-1: New USB device strings: Mfr=1, Product=2, SerialNumber=3
[ 3485.251794] usb 2-1: Product: GBA ST2
[ 3485.251795] usb 2-1: Manufacturer: Astrosystems
[ 3485.251796] usb 2-1: SerialNumber: 06010010001
[ 3485.260103] cdc_acm 2-1:1.0: ttyACM0: USB ACM device
$ lsusb -t
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/12p, 12M
|__ Port 1: Dev 4, If 0, Class=Communications, Driver=cdc_acm, 12M
|__ Port 1: Dev 4, If 1, Class=CDC Data, Driver=cdc_acm, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/12p, 480M
Showing that:
- 2-1:1.0 is assigned to
/dev/ttyACM0 - 2-1:1.1 is ignored
By playing around with the usbserial driver to assign the Data interface to a /dev/ttyUSBX port I found that the following manipulation sometimes works:
- plug-in the device and have it use the
cdc_acmdriver. This cause the device to exit its sleep mode (the device leds becomes green) - Switch to the
usbserialdriver usingmodprobe -r cdc_acm && modprobe usbserial vendor=0x16f9 product=0x0003, resulting in the Comm interface being ignored and Data interface assigned to a USB port - If the device goes back to sleep mode, it needs to be re-plugged and initialized again from step 1
When using the usbserial driver:
- 2-1:1.0 is ignored
- 2-1:1.1 is assigned to
/dev/ttyUSBX
Related dmesg and lsusb:
$ dmesg
[ 3688.481125] usbserial_generic 2-1:1.0: Generic device with no bulk out, not allowed.
[ 3688.481153] usbserial_generic: probe of 2-1:1.0 failed with error -5
[ 3688.481157] usbserial_generic 2-1:1.1: The "generic" usb-serial driver is only for testing and one-off prototypes.
[ 3688.481158] usbserial_generic 2-1:1.1: Tell [email protected] to add your device to a proper driver.
[ 3688.481160] usbserial_generic 2-1:1.1: generic converter detected
[ 3688.481219] usb 2-1: generic converter now attached to ttyUSB0
$ lsusb -t
/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=ohci-pci/12p, 12M
|__ Port 1: Dev 4, If 0, Class=Communications, Driver=, 12M
|__ Port 1: Dev 4, If 1, Class=CDC Data, Driver=usbserial_generic, 12M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=ehci-pci/12p, 480M
My guess is that the device use the CDC Communication interface to perform some sort of initialization, and then the CDC Data interface when in use.
How can I have both interfaces attached to a USB and/or ACM port? Should I implement my own driver (or extend the cdc_acm driver) to explicitely attach each descriptor to a USB or ACM port?
Here is a sample lsusb -v output showing the Communication interface on 2-1:1.0 and Data interface on 2-1:1.1:
Bus 002 Device 003: ID 16f9:0003
Device Descriptor:
bLength 18
bDescriptorType 1
bcdUSB 2.00
bDeviceClass 2 Communications
bDeviceSubClass 0
bDeviceProtocol 0
bMaxPacketSize0 64
idVendor 0x16f9
idProduct 0x0003
bcdDevice 14.06
iManufacturer 1 Astrosystems
iProduct 2 GBA ST2
iSerial 3 06010010001
bNumConfigurations 1
Configuration Descriptor:
bLength 9
bDescriptorType 2
wTotalLength 62
bNumInterfaces 2
bConfigurationValue 1
iConfiguration 0
bmAttributes 0xc0
Self Powered
MaxPower 100mA
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 0
bAlternateSetting 0
bNumEndpoints 1
bInterfaceClass 2 Communications
bInterfaceSubClass 2 Abstract (modem)
bInterfaceProtocol 1 AT-commands (v.25ter)
iInterface 4 GBA USB Serial Port
CDC Header:
bcdCDC 1.20
CDC ACM:
bmCapabilities 0x02
line coding and serial state
CDC Union:
bMasterInterface 0
bSlaveInterface 1
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x83 EP 3 IN
bmAttributes 3
Transfer Type Interrupt
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 50
Interface Descriptor:
bLength 9
bDescriptorType 4
bInterfaceNumber 1
bAlternateSetting 0
bNumEndpoints 2
bInterfaceClass 10 CDC Data
bInterfaceSubClass 0 Unused
bInterfaceProtocol 0
iInterface 4 GBA USB Serial Port
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x82 EP 2 IN
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Endpoint Descriptor:
bLength 7
bDescriptorType 5
bEndpointAddress 0x01 EP 1 OUT
bmAttributes 2
Transfer Type Bulk
Synch Type None
Usage Type Data
wMaxPacketSize 0x0040 1x 64 bytes
bInterval 0
Device Status: 0x0001
Self Powered
