pid tuning: set y axis limit to first point instead of 0

src/QmlControls/PIDTuning.qml

@@ -139,15 +139,22 @@ RowLayout {
             _xAxis.max = _msecs / 1000
             _xAxis.min = _msecs / 1000 - chartDisplaySec
 
+            var firstPoint = _msecs == 0
+
             var len = axis[_currentAxis].plot.length
             for (var i = 0; i < len; ++i) {
                 var value = axis[_currentAxis].plot[i].value
                 if (!isNaN(value)) {
                     chart.series(i).append(_msecs/1000, value)
+                    if (firstPoint) {
+                        _yAxis.min = value
+                        _yAxis.max = value
+                    } else {
                         adjustYAxisMin(_yAxis, value)
                         adjustYAxisMax(_yAxis, value)
                     }
                 }
+            }
 
             var t = new Date().getTime() // in ms
             if (_last_t > 0)