Subsections

Linux notes

All differences between the Windows and Linux version of Tscope are reported here. If a function is not mentioned in this section, it will behave identical on both operating systems.

ts_priority

From tscope version 168 onwards this function can actually increase the priority of your program when running on Linux. It must, however, be used with care. Here are some considerations:

On Linux systems the higher priority modes can only be selected when running as root. When a non-root user requests a higher priority the program writes a warning to the console and continues running with normal priority.
When running in X11 mode, increasing the priority of your program will slow down the X11 server. Therefore, it is necessary to suspend your program from time to time to allow the X11 server to display your stimuli, poll the mouse status, etc. The function ts_waitmode controls where and when Tscope will suspend your program. You will need to experiment with the different wait modes to find a good setting. Giving up too much cpu cycles will cause the vsync function to miss sync signals, keeping all cycles for yourself will slow down graphics.
Running in console mode (as root) seems the best option when running programs with increased priority. The only problem is that the current version of Allegro has trouble with usb mice on linux. On my system this could be fixed by telling Allegro to read the mouse state from /dev/input/eventN, by adding
```
[mouse]
mouse = EV
```
to the allegro configuration file. This configuration file can be found in the source directory of allegro and is called allegro.cfg. If you are using ts_scrcfg and ts_timercfg you will need to add this to your tscope.cfg file.
The good news, however, is that timing precision on Linux is already quite accurate when running with normal priority in X11 mode. Moreover, as in the Windows version, the *error parameter of the timing functions will accurately report the timing error of each timed event, so that trials where the timing error was too large can be filtered out afterwards.

Currently, Tscope uses a call to the function setpriority to change the priority of the program. The priority of a program could be uncreased even further by calling sched_setscheduler and mlockall, but this would also increase the risk of locking up your system.

ts_waitmode

On Linux, Tscope programs can give up short intervals of cpu time by blocking on a read of the real time clock (/dev/rtc). This allows other processes (such as X11) to run for a short time. When running a program with higher priority in X11 mode, the waitmode should be set to SLEEP_WAIT. This can, however, only be done when running as root. If a waitmode different from the default BUSYLOOP is requested by a non-root user, the program will write a warning to the console and will continue using the BUSYLOOP waitmode.

ts_defkey

Most input devices will work in the same way on Linux and on Windows. There are two minor differences:

The game and parallel port can only be read when running as root.
The cedrus usb serial response box is not supported on Linux.

ts_vsync

The logic for selecting a vsync mode differs from the Windows version for the following reasons:

Only root can read the status of the vsync signal from the registry.
The actual refresh rate can not be reported by Linux. In order to know the refreshrate of your screen, it is necessary to start your program with the desired graphics mode and then use your screen's menu to read out the refresh rate. This value can then be entered in your call to ts_refreshrate to make the vsync simulation work properly.

Under ideal circumstances, the function reads the status of vertical retrace signal directly from the computer's registry. In situations where that's not possible, a vertical retrace signal is simulated.

Tscope will simulate the retrace signal at the requested refresh rate in the following cases:

If no window is opened yet.
In windowed mode.
If the refresh rate is too high. Default the maximum value is 70Hz, but it can be altered by the function ts_vsynclimit.
If the vsync register cannot be opened. (i.e. if the user is not root).

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