NAME

       encoder_ratio - an electronic gear to synchronize two axes

SYNOPSIS

       loadrt encoder_ratio [num_chan=num | names=name1[,name2...]]

DESCRIPTION

       encoder_ratio  can be used to synchronize two axes (like an "electronic gear").  It counts
       encoder pulses from both axes in software, and produces an error value that  can  be  used
       with a PID loop to make the slave encoder track the master encoder with a specific ratio.

       This  module  supports  up  to eight axis pairs.  The number of pairs is set by the module
       parameter num_chan.  Alternatively, specify names= and unique names separated by commas.

       The num_chan= and names= specifiers are mutually  exclusive.   If  neither  num_chan=  nor
       names= are specified, the default value is one.

FUNCTIONS

       encoder-ratio.sample
              Read all input pins.  Must be called at twice the maximum desired count rate.

       encoder-ratio.update (uses floating-point)
              Updates all output pins.  May be called from a slower thread.

NAMING

       The names for pins and parameters are prefixed as:
         encoder-ratio.N. for N=0,1,...,num-1 when using num_chan=num
         nameN. for nameN=name1,name2,... when using names=name1,name2,...

       The encoder-ratio.N. format is shown in the following descriptions.

PINS

       encoder-ratio.N.master-A bit in
       encoder-ratio.N.master-B bit in
       encoder-ratio.N.slave-A bit in
       encoder-ratio.N.slave-B bit in
              The encoder channels of the master and slave axes

       encoder-ratio.N.enable bit in
              When the enable pin is FALSE, the error pin simply reports the slave axis position,
              in revolutions.  As such, it would normally be connected to the feedback pin  of  a
              PID block for closed loop control of the slave axis.  Normally the command input of
              the PID block is left unconnected (zero), so the  slave  axis  simply  sits  still.
              However  when  the enable input goes TRUE, the error pin becomes the slave position
              minus the scaled master position.  The scale factor is the ratio of master teeth to
              slave  teeth.   As  the master moves, error becomes non-zero, and the PID loop will
              drive the slave axis to track the master.

       encoder-ratio.N.error float out
              The error in the position of the slave (in revolutions)

PARAMETERS

       encoder-ratio.N.master-ppr unsigned rw
       encoder-ratio.N.slave-ppr unsigned rw
              The number of pulses per revolution of the master and slave axes

       encoder-ratio.N.master-teeth unsigned rw
       encoder-ratio.N.slave-teeth unsigned rw
              The number of "teeth" on the master and slave gears.

SEE ALSO

       encoder(9)