tweaked cal_postgain_binary() so it gets the least significant bit right

diff --git a/comedi_calibrate/comedi_calibrate.c b/comedi_calibrate/comedi_calibrate.c
index 2a0dafa8406a1162850744162e5670c1a47f90ab..8914680d74e9d9fa6dc8f4107bbcff771951beff 100644 (file)
--- a/comedi_calibrate/comedi_calibrate.c
+++ b/comedi_calibrate/comedi_calibrate.c
@@ -211,7 +211,7 @@ ok:
                        "insufficient information.\n"
                        "Please send this output to <ds@schleef.org>.\n"
                        "This output will also allow comedi_calibrate to execute more\n"
-                       "quickly in the future.");
+                       "quickly in the future.\n");
                if(verbose<1)verbose=1;
                if(device_status==STATUS_UNKNOWN){
                        do_reset=1;
@@ -525,70 +525,61 @@ void cal_binary( calibration_setup_t *setup, int obs, int dac)
 
 void cal_postgain_binary( calibration_setup_t *setup, int obs1, int obs2, int dac)
 {
-       int x1, x2, x;
-       double y1, y2, y;
+       int x0, x1, x2, x, polarity;
+       double y0, y1, y2;
        new_sv_t sv1, sv2;
        double target = setup->observables[obs1].target - setup->observables[obs2].target;
        unsigned int chanspec1 = setup->observables[obs1].observe_insn.chanspec;
        unsigned int chanspec2 = setup->observables[obs2].observe_insn.chanspec;
+       unsigned int bit;
 
        DPRINT(0,"postgain binary: %s, %s\n", setup->observables[obs1].name,
                setup->observables[obs2].name);
 
-       x1 = 0;
-       x2 = setup->caldacs[dac].maxdata;
-
-       update_caldac( setup, dac, x1 );
-       usleep(100000);
-       preobserve( setup, obs1);
-       new_sv_init(&sv1, setup->dev, setup->ad_subdev,chanspec1);
-       sv1.settling_time_ns = setup->settling_time_ns;
-       new_sv_measure( setup->dev, &sv1);
-       y1 = sv1.average;
-       preobserve( setup, obs2);
-       new_sv_init(&sv2, setup->dev, setup->ad_subdev,chanspec2);
-       sv2.settling_time_ns = setup->settling_time_ns;
-       new_sv_measure( setup->dev, &sv2);
-       y1 -= sv2.average;
-
-       update_caldac( setup, dac, x2 );
+       x0 = x1 = x2 = 0;
+       update_caldac( setup, dac, x0 );
        usleep(100000);
        preobserve( setup, obs1);
        new_sv_init(&sv1, setup->dev, setup->ad_subdev,chanspec1);
        sv1.settling_time_ns = setup->settling_time_ns;
        new_sv_measure( setup->dev, &sv1);
-       y2 = sv1.average;
+       y0 = sv1.average;
        preobserve( setup, obs2);
        new_sv_init(&sv2, setup->dev, setup->ad_subdev,chanspec2);
        sv2.settling_time_ns = setup->settling_time_ns;
        new_sv_measure( setup->dev, &sv2);
-       y2 -= sv2.average;
+       y0 -= sv2.average;
+       y1 = y2 = y0;
 
-       x = 0;
-       while(x2-x1 > 1){
-               x = (x1 + x2 + 1)/2;
-               DPRINT(3,"trying %d\n",x);
+       bit = 1;
+       while( ( bit << 1 ) < setup->caldacs[dac].maxdata )
+               bit <<= 1;
+       for( ; bit; bit >>= 1 )
+       {
+               x2 = x1 | bit;
 
-               update_caldac( setup, dac, x );
+               update_caldac( setup, dac, x2 );
                usleep(100000);
 
                preobserve( setup, obs1);
                new_sv_init(&sv1, setup->dev, setup->ad_subdev,chanspec1);
                sv1.settling_time_ns = setup->settling_time_ns;
                new_sv_measure( setup->dev, &sv1);
-               y = sv1.average;
+               y2 = sv1.average;
                preobserve( setup, obs2);
                new_sv_init(&sv2, setup->dev, setup->ad_subdev,chanspec2);
                sv2.settling_time_ns = setup->settling_time_ns;
                new_sv_measure( setup->dev, &sv2);
-               y -= sv2.average;
-
-               if(fabs(y2 - target) > fabs(y1 - target)){
-                       x2 = x;
-                       y2 = y;
-               }else{
-                       x1 = x;
-                       y1 = y;
+               y2 -= sv2.average;
+
+               DPRINT(3,"trying %d, result %g, target %g\n",x2,y2,target);
+
+               if( (y2 - y0) > 0.0 ) polarity = 1;
+               else polarity = -1;
+
+               if( (y2 - target) * polarity < 0.0 ){
+                       x1 = x2;
+                       y1 = y2;
                }
 
                if(verbose>=3){
@@ -599,6 +590,11 @@ void cal_postgain_binary( calibration_setup_t *setup, int obs1, int obs2, int da
                }
        }
 
+       if( fabs( y1 - target ) < fabs( y2 - target ) )
+               x = x1;
+       else
+               x = x2;
+       update_caldac( setup, dac, x );
        DPRINT(0,"caldac[%d] set to %d\n",dac,x);
        if(verbose>=3){
                preobserve( setup, obs1);