"usb_dev_serial" receiving unusual data not sent from host application

Hello Jatala,

Couple of things

1. When you start the example does it start with the USB peripheral being reset? I suspect a rerun of the code is causing it when a new code image is loaded and the example re-run
2. When the bytes are being received, can you check what the content of the RX byte is. The reason why I ask so is to see if there is some trend in the RX bytes which may suggest the source being your host application or a driver artifact.
3. To check the driver artifact a good idea (though not possible) would be analyze the USB traffic.
4. Without the modified code you have it would be tough for us to see where the issue is coming from.

Regards
Amit

Hello Amit,

Thanks for the response. Here is exactly what I am doing:

1. Connect the ubuntu 14.04 PC to the Device port, and the windows 7 PC to the Debug port with USB cables as shown in the attached picture. On the ubuntu PC I do not run my application to read/write data to the USB Device port (/dev/ttyACM0), no application opens the port. In fact I do nothing except connecting the device port to ubuntu. On windows PC I am running CCS and Putty: first I connect to the board through putty; afterwards I  launch the modified usb_dev_serial program through the CCS.

 

Here is log of events, along with received data

Tiva C Series USB Serial Device Example

---------------------------------

Configuring USB

Waiting for host...

Ct: USB_EVENT_SUSPEND

Ct: USB_EVENT_SUSPEND

Ct: Connected

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_LINE_CODING

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_LINE_CODING

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x41

Rx: 0,  Rx: 1, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x54

Rx: 1,  Rx: 2, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x0d

Rx: 2,  Rx: 3, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x41

Rx: 3,  Rx: 4, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x54

Rx: 4,  Rx: 5, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x0d

Rx: 5,  Rx: 6, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x41

Rx: 6,  Rx: 7, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x54

Rx: 7,  Rx: 8, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x0d

Rx: 8,  Rx: 9, -> 1

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_LINE_CODING

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x7e, 0x00, 0x78, 0xf0, 0x7e

Rx: 9,  Rx: 14, -> 5

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x7e, 0x00, 0x78, 0xf0, 0x7e

Rx: 14,  Rx: 19, -> 5

Rx: USB_EVENT_DATA_REMAINING

Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

2. In the second setup, both the device and debug ports of the board are connected with the windows PC as shown here

Similar to the ubuntu case, I do not run my application to read/write data to the USB Device port, no application opens the port. In fact I do nothing except connecting the device port to the PC. Afterwards, I connect to the Debug port through Putty, and  launch the modified usb_dev_serial program from CCS. Here is log of events.  no received data is reported in this case. 

Tiva C Series USB Serial Device Example
---------------------------------
Configuring USB
Waiting for host...
Ct: USB_EVENT_SUSPEND
Ct: Connected
Ct: USBD_CDC_EVENT_GET_LINE_CODING
Rx: USB_EVENT_DATA_REMAINING
Ct: USBD_CDC_EVENT_SET_CONTROL_LINE_STATE

I am struggling to make sense of why in the Ubuntu case, the USB CDC class driver is reporting received data.

Kind regards

Jatala

Jatala said:

Rx: 2,  Rx: 3, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x41 --> ASCII 'A'

Rx: 3,  Rx: 4, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x54 --> ASCII 'T'

Rx: 4,  Rx: 5, -> 1

Rx: USB_EVENT_RX_AVAILABLE

Rx Data: 0x0d --> ASCII  '/r'

Rx: 5,  Rx: 6, -> 1

 On next debug session remember also print character as ASCII, printing ASCII char or attaching a terminal was clear what mean cr (for Baud rate auto setting)  "AT/n".

Hello Tsuneo,

Thanks for the explaining the cause of the data. Should not the CDC class driver handle this control data, instead of passing it to the user Rx buffer.