On Fri, 2008-02-22 at 17:51 -0800, Kirk Wallace wrote: > I think hal_joystick.c: > > http://cvs.linuxcnc.org/cgi-bin/cvsweb.cgi/emc2/src/hal/user_comps/devices/hal_joystick.c?rev=1.2;content-type=text%2Fplain > > might be a good model to follow for making my modbus user-land > component. My guess would be that one would setup HAL and the the HAL > pins and then loop to update the inputs and outputs, but the joystick > pins are set up in the main loop. Why is that? > > There is a prefix parameter used to name the pins and buttons but not > the component itself: > ... > snprintf(name, HAL_NAME_LEN-1, "hal_joystick-%d", getpid()); > comp_id = hal_init(name); > ... > Is there a reason not to use the prefix here? > > Thanks. >
Another bit I don't understand: /* STEP 3: allocate shared memory for joystick data */ js_data = (hal_js_t *) hal_malloc(sizeof(hal_js_t)); if (js_data == 0) { printf( "ERROR: hal_malloc() failed\n"); hal_exit(comp_id); return -1; } hal_js_t is a defined variable type. sizeof(hal_js_t) is the memory size of this type. hal_malloc(sizeof(hal_js_t)) returns the memory location of this variable. I don't understand what (hal_js_t *) does. hal_js_t is a type so it is similar to (int *)? -- Kirk Wallace (California, USA http://www.wallacecompany.com/machine_shop/ Hardinge HNC lathe, Bridgeport mill conversion, doing XY now, Zubal lathe conversion pending) ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2008. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users