xSCOPE

xSCOPE is a high speed protocol between the host and the target which runs over an xLINK.

It enables high-speed communication with two primary uses:

• Probes, where data values are sent to probes as ‘records’ which can then be plotted on a graph

• IO, where the ‘write’ syscall (used for functions such as printf) sends data over xSCOPE for faster printing

• xSCOPE command line options
  • xcc options
  • xrun options
  • xgdbserver options
• xSCOPE performance figures
  • Transfer rates between the xCORE Tile and XTAG-3 or XTAG-4
  • Transfer rates between the XTAG-3 or XTAG-4 and Host PC
  • Host/target data throughput benchmarks
• xSCOPE target library
  • Example
  • Configuration API
  • Tracing API
• xSCOPE host library
  • Example
  • API

Related

• xSCOPE config file

• Using xSCOPE for fast “printf debugging”

xSCOPE FAQ

• How do I just use xSCOPE for fast printing?

  See the quick start guide: Using xSCOPE for fast “printf debugging” for basic xSCOPE usage.

• Do I need both the -fxscope compiler option and an xSCOPE config file?

  If you are not using a config.xscope file, you must specify the -fxscope option on the command line to use xSCOPE (e.g. when using xSCOPE target library). You do not need both.

• What is xSCOPE “offline mode”?

  xSCOPE “offline mode”, which is also known as “xSCOPE file” mode, is the mode of xSCOPE which sends all xSCOPE records to a .vcd file to be viewed later with a VCD viewer such as GTKWave. This does not affect the “fast printf” xSCOPE messages, which still get printed to stdout. It only affects probes.

• What is xSCOPE “realtime xSCOPE”?

  xSCOPE “realtime mode”, also known as “xSCOPE server” refers to the the mode of xSCOPE which sends all received records to an xSCOPE client implemented by the user. Note that the realtime property of the server is as opposed to “offline”. It does not possess any hard real-time behaviour.

• What happens if the throughput of messages is too high for xSCOPE to keep up?

  That depends on the configuration of xSCOPE. By default, they will get dropped. This can be changed by calling xscope_mode_lossless(). In lossless mode, the transmitting thread will be stalled until there is bandwidth in the system to send more data.

  If the throughput is extremely high and the host system is very overloaded, it is possible for the host USB stack to drop packets.

Common & Known Issues

• Cannot simultaneously use the xSCOPE config file and xSCOPE API xscope_register function:

  It is not possible to use both the xSCOPE config file and the xSCOPE API xscope_register() function simultaneously. The dynamic registration will be ignored if an xSCOPE config file is used. You should see a warning similar to “System is already registered, new registration call ignored” when running with xrun or xgdb.

• Cannot attach to a running program:

  xSCOPE cannot be attached to a running program. The xSCOPE connection must be initialized and synchronized when the program is initially loaded with xrun/xgdb.

• No output without --xscope on xrun/xgdb:

  If you build your program with xSCOPE I/O enabled but do not specify the --xscope option in the xrun or xgdb connect command, you will not see any xSCOPE output.

• Cannot print when using xSCOPE server

  If the client of the xSCOPE server supports the ‘print’ capability (as the default implementation does), then the xgdb/xrun executable will no longer handle printing the messages itself: the client is expected to print them.

• xSCOPE io only affects write syscalls

  xSCOPE ioMode only improves the speed of write syscalls. Other sycalls such as read still go over JTAG, so those will not see a speed increase. The xSCOPE fileio library offers a system to improve this performance.

• Using both xSCOPE io and the xSCOPE server will break file writing.

  All write syscalls will get forwarded to the server, without the file descriptor, and not handled by the syscall code which would handle the syscall on the host. Consider using xSCOPE fileio if you need to use xSCOPE io and the xSCOPE server simultaneously.

• Using xSCOPE timed io will prepend the timestamp to all write syscalls, not just print messages

  The timed io is a convenience feature, which will not work for all applications. Disable it if you want precise control over the exact content that gets written to file.

• Signal integrity issues

  xSCOPE is very fast, but is more likely to experience signal integrity issues on some hardware configurations, such as with long cables.

• Trying to use xSCOPE when the physical connection is not present will silently fail

  The xSCOPE systems do not check that the connection is functional before relying on it, so this is up to the individual developer to ensure the connection is available before trying to use it.