Hello All,

    I have an interesting question. The project is a robot arm in a closed
loop app using a potentiometer connected to the arm. The motor is activated
by an analog voltage input, which compares to the pot settings (and has
specific hysteresis points in the code). The pot  has a specific range
defined in increments preset by the user within the AtoD range. I am trying
to find a way in C (CCS) to fit variable, user-defined limits (LowLimit and
HighLimit) within the preset analog to digital limits and reset the AtoD
range to within the new user limits. The range on the AtoD is 0 to 5 volts,
set up with Vref to 5 volts. The user defined limits are defined as : 0v <
LowLimit < High Limit < 5v. The new range is found by : HighLimit - LowLimit
= Range. The problem is: How do I divide in CCS C to find the new ratio?
Normal float and long division will not provide a divisor that is usable for
the steps within the ratio. I have read all the information about floats,
atod calculations, etc. but I have not found any app such as this.....

Pseudo Code

    long Range;                                        // Pot values low to
high
    long LowLimit;                                   // Lower Pot value
limit => 0 v
    long HighLimit;                                   // Higher Pot value
limit =< 5 v
    long increment;                                   // New range of pot
positions
    long PotPosition;                                // Measured input of
pot position
    long MeasVal;                                   // User input voltage 0
to 5 volts
    long PotVal ;                                      // Pot Position
measurement
    int input=0;                                        // Analog
measurement channel
    int pot=1;                                          // Analog
measurement channel

    MeasVal  = measure_routine(input);            // Get new input value to
fit within range
    PotVal   = measure_routine(pot);              // Get pot value

    Range = HighLimit - LowLimit;          // determines range of new limits

    increment = Range / 1023;                 // 0x3ff full range of atod
gives new increment
***** Here is the issue, cannot find a way to do this and get a number that
makes this work:
     PotPosition = MeasVal * increment; // Gives new position for the pot

    Code would then compare the analog voltage input to the PotPosition
reading, then move the motor accordingly. The new limits correspond to the
old zero and five volt limits, and have limits on how small the range can be
before range becomes unusable.

    The issue remains: How do you calculate the new position within the new
range?

    Any thoughts?

    Jack Wilker

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