================
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

  #. 8-bits of the trace ID (values associated with the above)
  #. 8-bits of additional trace ID data, and
  #. 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:

==  ====================  ================  ==================================  =================
N.  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``:
     
     .. code-block:: 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``:
     
      .. code-block:: 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.