Raspberry Pi にインストールした Node-RED でLEDの制御をしてみる##
使用環境
- Raspberry Pi
- Node-RED + node-red-node-pi-gpio + node-red-dashboard
- ブレッドボード
- LED
- 抵抗（1kΩ程度）
- ブレッドボード用ワイヤ（オス―メス）
1. Raspberry Pi に接続したLEDのON/OFF
Node-RED を起動してフローエディタで node-red-node-pi-gpio と node-red-dashboard がインストールされていることを確認します。
ボタンとrpi gpio out をフローに追加します。
rpi gpio out は、使用するピン番号を選択します。設定後、各ノードをワイヤで結びます。
実物の回路を作成します。rpi gpio out で設定したピンとブレッドボードの抵抗－LED－Raspberry Pi の GND とワイヤで接続します。
Node-RED のフローをデブロイし、ダッシュボードを表示します。ボタンをクリックするとLEDが点灯／消灯すると思います。
2. Slider で明るさ制御
１．で作成したフローのボタンの代わりにスライダーを使って、LEDの明るさを制御してみましょう。
rpi gpio out の設定画面で、pwm出力を選択し、スライダの出力値も0から100とします。
gauge も追加してスライダの値を表示するようにしてみましょう。
フローが完成したらデブロイして動作確認してみましょう。
3. OFF時の値を記憶、ONで復元
２．で slider を利用して LED の明るさ制御ができたので、button を追加して、以下の機能を追加してみましょう。
① OFF ボタンを追加、クリックすると、slider の値を記憶し、slider の値を 0 にする。
② ON ボタンを追加、クリックすると、①で記憶した値が slider にセットされ元の明るさに戻る
解説
グローバル変数を利用してスライダの値を記憶しています。
ひとつの変数でできそうな気もしていますが、ふたつ使用しています。OFFにした時のスライダの値をグローバル変数に入れて、ONにするときに戻す。というフローなのですが、スライダの値を常にグローバル変数に入れておいて、Off時にその値を記憶用のグローバル変数に入れるという２度手間をしています。変数ひとつでは、なぜかかうまく行きません。
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修正 ###
かなり恥ずかしい・・・
変数の使用は、injection してからと、勝手に思い込んでました。いきなり使えます。
次のように変更します。
変数のスコープも flow に変更しました。
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