Hi folks, I normally post over at FS.com, but browse here too (not often enough though...had to sign-up again. )I'm having problems coding a radar altimeter gauge. I think I have the math correct, but something in my callback code throughs a warning in VC++5 during the build. If I click through the warning, it will compile but the gauge needle is non-functional and stays frozen on 0 meters.Here's a code snip that includes the needle macro and callback.

//////////////////////////////////////////////////////////////////////// interpreted from post#3186 at FS.com panel forum////////////////////////////////////////////////////////////////////// UINT32 Ground = 0;  //set variables to 0UINT32 Plane = 0;UINT32 Ralt = 0;MODULE_VAR		PHeight = {PLANE_ALTITUDE};  //get plane altMODULE_VAR		GHeight = {GROUND_ALTITUDE}; //get ground alt////////////needle macro callback/////////////////////////////FLOAT64 FSAPI ralt_cb (PELEMENT_ICON pelement){int val;lookup_var(&PHeight);			//get Plane Altlookup_var(&GHeight);			//get Ground AltPlane == PHeight.var_value.n;	//Plane Alt in metersGround == GHeight.var_value.n;	//Ground Alt in (meters * 256)Ground == Ground/256;			//Ground Alt converted back to metersRalt == Plane - Ground;			//altitude of plane above terrain...I want this as my returned value. val = (Ralt);	return val;}//////////////////////////////////////////////////////////MAKE_NEEDLE(	ralt_needle,	BMP_RALT_NEEDLE,	NULL,	ralt_fail,	IMAGE_USE_TRANSPARENCY | IMAGE_USE_ERASE | BIT7,	0,	150, 150,	0, 7,	MODULE_VAR_NONE,ralt_cb,		ralt_nonlinearity,	6)PELEMENT_HEADER		ralt_needle_list[] ={	(PELEMENT_HEADER)&ralt_needle,	NULL};////////////////////////////////////////////////////////////////////////

Any ideas are welcome. Thanks!Mike

The reason for the warning is that you use an icon callback for a needle element (PELEMENT_ICON instead of PELEMENT_NEEDLE) Since do not access any of the pelement->.. variables it doesn't do any harm.The reason why it is stuck is a different one, you use the equality operator "==" where you need the assingment operator "=". By the way, there is a variable RADIO_HEIGHT for your purpose, it wasn't there is FS98 but it is now.Arne Bartels

DOH! That's two that I overlooked.Thanks Arne!