adding pid

docs/examples/line-follower-pid.md

@@ -1,3 +1,4 @@
+# Gradien follower PID + calibration
 
 ```blocks
 let lasterror = 0
@@ -5,12 +6,45 @@ let D = 0
 let I = 0
 let P = 0
 let error = 0
+let setpoint = 0
+let max = 0
+let min = 0
+let v = 0
+v = sensors.color3.light(LightIntensityMode.Reflected)
+min = v
+max = v
+setpoint = v
+while (!(brick.buttonEnter.wasPressed())) {
+    brick.clearScreen()
+    brick.showString("Move robot on terrain", 1)
+    brick.showString("Press ENTER when done", 2)
+    v = sensors.color3.light(LightIntensityMode.Reflected)
+    min = Math.min(min, v)
+    max = Math.max(max, v)
+    setpoint = (max + min) / 2
+    brick.showValue("v", v, 3)
+    brick.showValue("min", min, 4)
+    brick.showValue("max", v, 5)
+    brick.showValue("setpoint", setpoint, 6)
+    loops.pause(100)
+}
 loops.forever(function () {
-    error = sensors.color3.light(LightIntensityMode.Reflected) - 35
+    brick.clearScreen()
+    v = sensors.color3.light(LightIntensityMode.Reflected)
+    brick.showValue("light", v, 1)
+    error = v - setpoint
+    brick.showValue("error", error, 2)
     P = error * 5
+    brick.showValue("P", P, 3)
     I = I + error * 0.01
+    brick.showValue("I", I, 4)
     D = (error - lasterror) * 0.2
+    brick.showValue("D", D, 5)
     motors.largeBC.steer(P + (I + D), 100)
     lasterror = error
+    if (brick.buttonEnter.wasPressed()) {
+        motors.largeBC.setSpeed(0)
+        brick.buttonDown.pauseUntil(ButtonEvent.Click)
+    }
 })
 ```