I want to implement a linear fade function. In the 16c74. 

       dac output
        |                    FadeInLevel
        |                *  *  *              *  *  *  *  
        |         * |                       | *  
        |           *   |                               |   *
        |        *      |                               |     *
        |     *         |                               |       *  *  *  * 
FadeOutLevel 
        |_*_______|_________________ |_____|_____________ time
        |           |                           |        |
              FadeInTime                             FadeOutTime


The fading should be controlled by setting a FadeInTime, FadeInLevel,
FadeOutTime, FadeOutLevel

I guess the fade function will look like
       dac output
        |
tv      |                *  
        |         *
        |           *  
        |        *     
        |     *        
sv      |_*______________________ time
         st               ft

sv = start value
tv = target value
st = start time
ft = fade time

        for a certain point X on the time axis I have a dac output value Y
        
                (tv - sv) * (X - st)
        Y = --------------------------- + sv
                (ft - st)

the start time st will be always be zero

                (tv - sv) * X 
        Y = ------------------ + sv
                ft 
The time interval will be something around 10 or 20ms



Does anybody have experience with this (prefered Mplabc)

Frank Temmerman