USB Device Trace

USB Device Tracing Controls. The NuttX USB device subsystem supports a fairly sophisticated tracing facility. The basic trace cabability is controlled by these NuttX configuration settings:

  • CONFIG_USBDEV_TRACE: Enables USB tracing

  • CONFIG_USBDEV_TRACE_NRECORDS: Number of trace entries to remember

Trace IDs. The trace facility works like this: When enabled, USB events that occur in either the USB device driver or in the USB class driver are logged. These events are described in include/nuttx/usb/usbdev_trace.h. The logged events are identified by a set of event IDs:

TRACE_INIT_ID

Initialization events

TRACE_EP_ID

Endpoint API calls

TRACE_DEV_ID

USB device API calls

TRACE_CLASS_ID

USB class driver API calls

TRACE_CLASSAPI_ID

Other class driver system API calls

TRACE_CLASSSTATE_ID

Track class driver state changes

TRACE_INTENTRY_ID

Interrupt handler entry

TRACE_INTDECODE_ID

Decoded interrupt event

TRACE_INTEXIT_ID

Interrupt handler exit

TRACE_OUTREQQUEUED_ID

Request queued for OUT endpoint

TRACE_INREQQUEUED_ID

Request queued for IN endpoint

TRACE_READ_ID

Read (OUT) action

TRACE_WRITE_ID

Write (IN) action

TRACE_COMPLETE_ID

Request completed

TRACE_DEVERROR_ID

USB controller driver error event

TRACE_CLSERROR_ID

USB class driver error event

Logged Events. Each logged event is 32-bits in size and includes

  1. 8-bits of the trace ID (values associated with the above)

  2. 8-bits of additional trace ID data, and

  3. 16-bits of additional data.

8-bit Trace Data The 8-bit trace data depends on the specific event ID. As examples,

  • For the USB serial and mass storage class, the 8-bit event data is provided in include/nuttx/usb/usbdev_trace.h.

  • For the USB device driver, that 8-bit event data is provided within the USB device driver itself. So, for example, the 8-bit event data for the LPC1768 USB device driver is found in arch/arm/src/lpc17xx_40xx/lpc17_40_usbdev.c.

16-bit Trace Data. The 16-bit trace data provided additional context data relevant to the specific logged event.

Trace Control Interfaces. Logging of each of these kinds events can be enabled or disabled using the interfaces described in include/nuttx/usb/usbdev_trace.h.

Enabling USB Device Tracing. USB device tracing will be configured if CONFIG_USBDEV and either of the following are set in the NuttX configuration file:

  • CONFIG_USBDEV_TRACE, or

  • CONFIG_DEBUG_FEATURES and CONFIG_DEBUG_USB

Log Data Sink. The logged data itself may go to either (1) an internal circular buffer, or (2) may be provided on the console. If CONFIG_USBDEV_TRACE is defined, then the trace data will go to the circular buffer. The size of the circular buffer is determined by CONFIG_USBDEV_TRACE_NRECORDS. Otherwise, the trace data goes to console.

Example. Here is an example of USB trace output using apps/examples/usbserial for an LPC1768 platform with the following NuttX configuration settings:

  • CONFIG_DEBUG_FEATURES, CONFIG_DEBUG_INFO, CONFIG_USB

  • CONFIG_EXAMPLES_USBSERIAL_TRACEINIT, CONFIG_EXAMPLES_USBSERIAL_TRACECLASS, CONFIG_EXAMPLES_USBSERIAL_TRACETRANSFERS, CONFIG_EXAMPLES_USBSERIAL_TRACECONTROLLER, CONFIG_EXAMPLES_USBSERIAL_TRACEINTERRUPTS

Console Output:

      ABDE
      usbserial_main: Registering USB serial driver
      uart_register: Registering /dev/ttyUSB0
      usbserial_main: Successfully registered the serial driver
1     Class API call 1: 0000
2     Class error: 19:0000
      usbserial_main: ERROR: Failed to open /dev/ttyUSB0 for reading: 107
      usbserial_main: Not connected. Wait and try again.
3     Interrupt 1 entry: 0039
4     Interrupt decode 7: 0019
5     Interrupt decode 32: 0019
6     Interrupt decode 6: 0019
7     Class disconnect(): 0000
8     Device pullup(): 0001
9     Interrupt 1 exit: 0000

The numbered items are USB USB trace output. You can look in the file drivers/usbdev/usbdev_trprintf.c to see examctly how each output line is formatted. Here is how each line should be interpreted:

USB EVENT ID

8-bit EVENT DATA

MEANING

16-bit EVENT DATA

1

TRACE_CLASSAPI_ID1

1

USBSER_TRACECLASSAPI_SETUP1

0000

2

TRACE_CLSERROR_ID1

19

USBSER_TRACEERR_SETUPNOTCONNECTED1

0000

3

TRACE_INTENTRY_ID1

1

LPC17_40_TRACEINTID_USB2

0039

4

TRACE_INTDECODE_ID2

7

LPC17_40_TRACEINTID_DEVSTAT2

0019

5

TRACE_INTDECODE_ID2

32

LPC17_40_TRACEINTID_SUSPENDCHG2

0019

6

TRACE_INTDECODE_ID2

6

LPC17_40_TRACEINTID_DEVRESET2

0019

7

TRACE_CLASS_ID1

3

(See TRACE_CLASSDISCONNECT1)

0000

8

TRACE_DEV_ID1

6

(See TRACE_DEVPULLUP1)

0001

9

TRACE_INTEXIT_ID1

1

LPC17_40_TRACEINTID_USB2

0000

NOTES:

  1. See include/nuttx/usb/usbdev_trace.h

  2. See arch/arm/src/lpc17xx_40xx/lpc17_40_usbdev.c

In the above example you can see that:

  • 1. The serial class USB setup method was called for the USB serial class. This is the corresponds to the following logic in drivers/usbdev/pl2303.c:

    static int pl2303_setup(FAR struct uart_dev_s *dev)
{
  ...
  usbtrace(PL2303_CLASSAPI_SETUP, 0);
  ...

  • 2. An error occurred while processing the setup command because no configuration has yet been selected by the host. This corresponds to the following logic in drivers/usbdev/pl2303.c:

    static int pl2303_setup(FAR struct uart_dev_s *dev)
{
  ...
  /* Check if we have been configured */

  if (priv->config == PL2303_CONFIGIDNONE)
    {
      usbtrace(TRACE_CLSERROR(USBSER_TRACEERR_SETUPNOTCONNECTED), 0);
      return -ENOTCONN;
    }
  ...

  • 3-6. Here is a USB interrupt that suspends and resets the device.

  • 7-8. During the interrupt processing the serial class is disconnected

  • 9. And the interrupt returns

USB Monitor. The USB monitor is an application in the apps/system/usbmonitor that provides a convenient way to get debug trace output. If tracing is enabled, the USB device will save encoded trace output in in-memory buffer; if the USB monitor is also enabled, that trace buffer will be periodically emptied and dumped to the system logging device (the serial console in most configurations). The following are some of the relevant configuration options:

Device Drivers -> USB Device Driver Support

.

CONFIG_USBDEV_TRACE=y

Enable USB trace feature

CONFIG_USBDEV_TRACE_NRECORDS=nnnn

Buffer nnnn records in memory. If you lose trace data,

.

then you will need to increase the size of this buffer

.

(or increase the rate at which the trace buffer is emptied).

CONFIG_USBDEV_TRACE_STRINGS=y

Optionally, convert trace ID numbers to strings.

.

This feature may not be supported by all drivers.

Application Configuration -> NSH LIbrary

.

CONFIG_NSH_USBDEV_TRACE=n

Make sure that any built-in tracing from NSH is disabled.

CONFIG_NSH_ARCHINIT=y

Enable this option only if your board-specific logic

.

has logic to automatically start the USB monitor.

.

Otherwise the USB monitor can be started or stopped

.

with the usbmon_start and usbmon_stop commands from the NSH console.

Application Configuration -> System NSH Add-Ons

.

CONFIG_USBMONITOR=y

Enable the USB monitor daemon

CONFIG_USBMONITOR_STACKSIZE=nnnn

Sets the USB monitor daemon stack size to nnnn. The default is 2KiB.

CONFIG_USBMONITOR_PRIORITY=50

Sets the USB monitor daemon priority to nnnn.

.

This priority should be low so that it does not

.

interfere with other operations, but not so low that

.

you cannot dump the buffered USB data sufficiently

.

rapidly. The default is 50.

CONFIG_USBMONITOR_INTERVAL=nnnn

Dump the buffered USB data every nnnn seconds.

.

If you lose buffered USB trace data, then dropping

.

this value will help by increasing the rate at which

.

the USB trace buffer is emptied.

CONFIG_USBMONITOR_TRACEINIT=y

Selects which USB event(s) that you want to be traced.

CONFIG_USBMONITOR_TRACECLASS=y

.

CONFIG_USBMONITOR_TRACETRANSFERS=y

.

CONFIG_USBMONITOR_TRACECONTROLLER=y

.

CONFIG_USBMONITOR_TRACEINTERRUPTS=y

.

NOTE: If USB debug output is also enabled, both outputs will appear on the serial console. However, the debug output will be asynchronous with the trace output and, hence, difficult to interpret.