{
  "format": "evn-blocks",
  "version": 3,
  "title": "Controllers: minimal",
  "needs": "a robot: left wheel motor on port 4 (mounted mirrored), right on port 3, 62.4 mm wheels 170 mm apart; an EVN colour sensor on I2C port 2 facing the floor a few mm up, over the edge of a dark line on a light floor",
  "description": "A line follower: a PID controller, made once and kept in the variable pid, turns the robot from the brightness of the floor under the colour sensor, so the robot follows the edge of the line for 10 s, then stops. Tune kp first (the wobble), then kd (the damping), then ki (the steady pull to one side). A second controller is a second variable: as many as the program needs.",
  "workspace": {
    "blocks": {
      "languageVersion": 0,
      "blocks": [
        {
          "type": "evn_setup_start",
          "id": "$0jKNQehs+y?%c0;(d@Z",
          "x": 20,
          "y": -40,
          "deletable": false,
          "next": {
            "block": {
              "type": "evn_motor_setup",
              "id": "Ju{5B!LeIDjWjr-Z,S0o",
              "fields": {
                "PORT": "4",
                "DIRECTION": "CCW",
                "UNIT": "DEG_S"
              },
              "next": {
                "block": {
                  "type": "evn_drivebase_setup",
                  "id": ")e*,G%fCqd`AJVTZCZj]",
                  "fields": {
                    "LEFT": "4",
                    "RIGHT": "3",
                    "WHEEL": 62.4,
                    "TRACK": 170
                  },
                  "next": {
                    "block": {
                      "type": "evn_colorsensor_setup",
                      "id": "S)mcPX1Or//{f=^.ZxsT",
                      "fields": {
                        "PORT": "2"
                      }
                    }
                  }
                }
              }
            }
          }
        },
        {
          "type": "evn_program_start",
          "id": "L-9khU6Wd6BM{ZUX~A{7",
          "x": 20,
          "y": 200,
          "deletable": false,
          "next": {
            "block": {
              "type": "variables_set",
              "id": "set_1",
              "fields": {
                "VAR": {
                  "id": "ctl_pid"
                }
              },
              "inputs": {
                "VALUE": {
                  "block": {
                    "type": "evn_pid_create",
                    "id": "make_2",
                    "fields": {
                      "KP": 1.5,
                      "KI": 0.2,
                      "KD": 0.08,
                      "LIMIT": 120
                    }
                  }
                }
              },
              "next": {
                "block": {
                  "type": "controls_repeat_ext",
                  "id": "4q=A-m8fLa`f!{QlTOmr",
                  "inputs": {
                    "TIMES": {
                      "shadow": {
                        "type": "math_number",
                        "id": "B~Ycfw,4Io6yiQd$YG%X",
                        "fields": {
                          "NUM": 1000
                        }
                      }
                    },
                    "DO": {
                      "block": {
                        "type": "evn_drivebase_drive",
                        "id": "7uIDzYjVnUj`^x@|zw%H",
                        "inputs": {
                          "SPEED": {
                            "shadow": {
                              "type": "math_number",
                              "id": "SxveSedeO@V%J(AUAS?d",
                              "fields": {
                                "NUM": 120
                              }
                            }
                          },
                          "TURN": {
                            "block": {
                              "type": "evn_ctrl_update",
                              "id": "R0ZlMli]epuTN!.e]CW)",
                              "fields": {
                                "VAR": {
                                  "id": "ctl_pid"
                                }
                              },
                              "inputs": {
                                "TARGET": {
                                  "shadow": {
                                    "type": "math_number",
                                    "id": "s]ZXLO+`vJfkkl{@^$,$",
                                    "fields": {
                                      "NUM": 34
                                    }
                                  }
                                },
                                "MEASURED": {
                                  "block": {
                                    "type": "evn_colorsensor_channel",
                                    "id": "34uWk^v`jXU~?:E??OT)",
                                    "fields": {
                                      "PORT": "2",
                                      "WHAT": "hsv().v"
                                    }
                                  }
                                }
                              }
                            }
                          }
                        },
                        "next": {
                          "block": {
                            "type": "evn_wait",
                            "id": "ppr90Bc)_sd38XU)Yesg",
                            "inputs": {
                              "TIME": {
                                "shadow": {
                                  "type": "math_number",
                                  "id": "n4;~g4mzy+z_JS3wee5,",
                                  "fields": {
                                    "NUM": 10
                                  }
                                }
                              }
                            }
                          }
                        }
                      }
                    }
                  },
                  "next": {
                    "block": {
                      "type": "evn_drivebase_stop",
                      "id": "YE|H0`[HMV0Ya{Qb{yA)",
                      "fields": {
                        "ACTION": "stop"
                      }
                    }
                  }
                }
              }
            }
          }
        }
      ]
    },
    "variables": [
      {
        "name": "pid",
        "id": "ctl_pid"
      }
    ]
  }
}