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RPi Node-Red: Advanced Multi-Button Board + RGB LED

RPi Node-Red: Advanced Multi-Button Board + RGB LED

Overview

This tutorial will utilize a multi-button board input device to control an RGB LED module. Students will learn about and utilize binary counting to program the multi-button board. This tutorial adds to prior knowledge on the Button + LED tutorial.

Requirements

  • Raspberry Pi 3 Model B
  • Multi-Button Board
  • RGB LED Module
  • F-F Jumper Cables

Getting Started

Setting up the Hardware

Multi-Button Board to Raspberry Pi

  • K1 to #6
  • K2 to #5
  • K3 to #22
  • K4 to #27
  • K5 to #17
  • K6 to #4
  • K7 to #21
  • K8 to #20
  • G to GND

RGB LED to Raspberry Pi

  • R to #13
  • G to #19
  • B to #26
  • GND to GND

Setting up Node-Red

  1. Insert RPi-GPIO-In Nodes
    1. These nodes act as inputs from the multi-button board.
    2. Place 8 nodes, representing the 8 button inputs.
    3. Assign each button (K1, K2…, K8) to their respective GPIO pin on the Raspberry Pi.
    4. Set the Resistor setting to pullup.
    5.  
  2. Insert Change Nodes
    1. These nodes translate the input nodes from the multi-button board into number values from 0 to 7 (numbering starts at 0 due to how computers start counting at 0 instead of 1).
    2. Place 8 nodes, labeling them from 0 to 7.
    3. For each node, change the data type to number and set the values to 0-7 starting with the first node.
  3. Connect an RPi-GPIO-In node to a Change node
    1. Connecting the two node types translates each binary 0 or 1 button input into a different decimal value.
  4. Insert Function Nodes
    1. These nodes act as “decoders” that translates the numbered value into a bit-string.
    2. The RGB values represent three individual switches. By having a bit-string representation, each bit can determine the color’s bit state.
    3. Function for [4] node
      1. // Value retrieved from initial input
        var value = msg.payload;
        
        // subtract_bit determined by bit location
        var subtract_bit = 4;
        
        // If value is greater than the subtract_bit, indicates that the bit state for [4] is 1
        if (value >= subtract_bit) {
            var new_value = {payload: value - subtract_bit};
            var bit_state = {payload: 1};
            return [new_value, bit_state];
        }
        
        // Otherwise, bit state for [4] is 0
        else {
            value = {payload: value};
            var bit_state = {payload: 0};
            return [value, bit_state];
        }
    4. Function for [2] node
      1. // Value retrieved from initial input
        var value = msg.payload;
        
        // subtract_bit determined by bit location
        var subtract_bit = 2;
        
        // If value is greater than the subtract_bit, indicates that the bit state for [2] is 1
        if (value >= subtract_bit) {
            var new_value = {payload: value - subtract_bit};
            var bit_state = {payload: 1};
            return [new_value, bit_state];
        }
        
        // Otherwise, bit state for [2] is 0
        else {
            value = {payload: value};
            var bit_state = {payload: 0};
            return [value, bit_state];
        }
    5. Function for [1] node
      1. var bit_state = {payload: msg.payload};
        return bit_state;
  5. Insert RPi-GPIO-Out Nodes
    1. These nodes act as output nodes for the RGB LED module.
    2. Place three nodes, each representing one of the RGB LEDs and assign to their respective GPIO pin.

Conclusion

If you have successfully followed this tutorial module, you should be able to change the RGB LED module’s color from the multi-button board.

Node-Red Solution

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subtract_bit};\n    var bit_state = {payload: 1};\n    return [new_value, bit_state];\n}\n\n// Otherwise, bit state for [4] is 0\nelse {\n    value = {payload: value};\n    var bit_state = {payload: 0};\n    return [value, bit_state];\n}","outputs":2,"noerr":0,"x":590,"y":340,"wires":[["fb4d798f.1edc38"],["a17a86af.bfb648"]]},{"id":"fb4d798f.1edc38","type":"function","z":"b8b26cb8.1baef","name":"[2]","func":"// Value retrieved from initial input\nvar value = msg.payload;\n\n// subtract_bit determined by bit location\nvar subtract_bit = 2;\n\n// If value is greater than the subtract_bit, indicates that the bit state for [2] is 1\nif (value >= subtract_bit) {\n    var new_value = {payload: value - subtract_bit};\n    var bit_state = {payload: 1};\n    return [new_value, bit_state];\n}\n\n// Otherwise, bit state for [2] is 0\nelse {\n    value = {payload: value};\n    var bit_state = {payload: 0};\n    return [value, bit_state];\n}","outputs":2,"noerr":0,"x":730,"y":360,"wires":[["bb73fc3f.28e14"],["74e9a7d8.f4a0e8"]]},{"id":"bb73fc3f.28e14","type":"function","z":"b8b26cb8.1baef","name":"[1]","func":"var bit_state = {payload: msg.payload};\nreturn bit_state;","outputs":1,"noerr":0,"x":870,"y":380,"wires":[["9a25ca9f.d2dca8"]]},{"id":"a17a86af.bfb648","type":"rpi-gpio out","z":"b8b26cb8.1baef","name":"Red","pin":"33","set":"","level":"0","freq":"","out":"out","x":750,"y":280,"wires":[]},{"id":"74e9a7d8.f4a0e8","type":"rpi-gpio out","z":"b8b26cb8.1baef","name":"Green","pin":"35","set":"","level":"0","freq":"","out":"out","x":890,"y":300,"wires":[]},{"id":"9a25ca9f.d2dca8","type":"rpi-gpio out","z":"b8b26cb8.1baef","name":"Blue","pin":"37","set":"","level":"0","freq":"","out":"out","x":1030,"y":320,"wires":[]}]
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