0. Another 'brute force' method of removing TT data. This time we
   remove the TT infomation from the DM voltages:

1. summary:

   // cal temp primary out

   delta_drive[a] = pr_sign * lp->data.inverse[a][s] * signal[s]

   temp_primary_out[a] = lp->data.primary_out[a] + (lp->data.delta_drive[a] * lp->parm.pr_gain)

   // take out tilt-from using temp primary_out.

   tt_dd[a] =  tt_sign * ttdm_inverse[a][s] * temp_primary_out[s]

   pr_out_tt[s] = input_imat[s][a] * tt_dd[a];

   temp_primary_out[a] = temp_primary_out[a] - (pr_out_tt[s] * gain2);

   // output to hardware:

   primary_out = temp_primary_out[a];


2. source code:

/*------------------------------------------------------------------
**  pr_servo_remove_tt() -  performs the primary loop. but first tries
**    to remove the tt information from the sigal[s] data.
**------------------------------------------------------------------
*/
static int pr_servo_remove_tt( lp_shmem_t * lp )
{
   int a, s;
   double total, out;
   float temp_primary_out[AO_NUM_P_ACTUATORS];
   float pr_out_tt[AO_NUM_P_ACTUATORS];
   float tt_dd[AO_NUM_TT_ACTUATORS];

   lp->status.lp_indicator |= 0x02;

   /******************************************************************
   ** cal temp_primary_out[a]
   ******************************************************************
   */

   /*--------------------------------------------------------
   **   delta_drive[a] = pr_sign * inverse[a][s] * signal[s]
   **    Note: using modified signal[s]
   */
   for (a=0; a<AO_NUM_P_ACTUATORS; a++)
   {
      total = 0.0;
      for (s=0; s<AO_NUM_SENSORS; s++)
         total += lp->data.inverse[a][s] * lp->data.signal[s];
      lp->data.delta_drive[a] = lp->parm.pr_sign * total;
   }

   /*--------------------------------------------
   ** temp_primary_out[a] = delta_drive[a] * pr_gain
   */
   for( a=0; a<AO_NUM_P_ACTUATORS; a++ )
   {
      temp_primary_out[a] = lp->data.primary_out[a] + (lp->data.delta_drive[a] * lp->parm.pr_gain);
   }

   /******************************************************************
   ** try to take out tilt from temp_primary_out[a]
   ******************************************************************
   */

   /*---------------------------------------------------------------
   **  tt_dd[a] = tt_sign * (ttdm_inverse[a][s] * temp_primary_out[s] )
   */
   for (a=0; a<AO_NUM_TT_ACTUATORS; a++)
   {
      total = 0.0;
      for (s=0; s<AO_NUM_P_ACTUATORS; s++)
         total += lp->data.ttdm_inverse[a][s] * temp_primary_out[s];
      tt_dd[a] = lp->parm.tt_sign * total;
   }
   /*---------------------------------------------------------------
   **  pr_out_tt[s] = input_imat[s][a] * tt_dd[a]
   **  cal pr_out values related only to tiptilt.
   */
   for (s=0; s<AO_NUM_P_ACTUATORS; s++)
   {
      total = 0.0;
      for (a=0; a<AO_NUM_TT_ACTUATORS; a++)
         total += lp->data.input_imat[s][a] * tt_dd[a];
      pr_out_tt[s] = total;
   }

   /*---------------------------------------------------------------
   ** temp_primary_out[a] = temp_primary_out[a] - (pr_out_tt[a] * pr_gain2)
   ** removes tiptilt component from temp_primary_out[a]
   */
   for (a=0; a<AO_NUM_P_ACTUATORS; a++)
   {
      temp_primary_out[a]  = temp_primary_out[a] - (pr_out_tt[a] * lp->parm.pr_gain2);
   }

   /******************************************************************
   * perform primary loop using modified signal[s]
   ******************************************************************
   */

   /*--------------------------------------------
   ** primary_out[a] = delta_drive[a] * pr_gain
   */
   for( a=0; a<AO_NUM_P_ACTUATORS; a++ )
   {
      set_primary_out( lp, a, temp_primary_out[a] );
   }
   return 0;
}