[Upcycle It] Interactive Race Car Driver - We have the technology to rebuild him

After the various modifications, repairs and tests it was time to put the Furby back together. The speaker wires were soldered in place and all the cables hot glued to act as a basic strain relief. A hole was made through the battery box to route the wires through to the Edison (via the level shifters). The power cables were extended and a couple of damaged links on the board were replaced. Once that was done the case could be re-assembled.

Power

As mentioned previously the Edison needs 7v to be able to power the board and USB correctly. To support this a boost regulator was added to the circuit based on the popular XL6009 chip. I initially planned to keep the 5v regulator from the origional battery box but that was not working when I tried it. Instead, I added a switch so that the battery can be switched between charging and powering. This can also be used as an off switch. I used the 100Ω high power resistor from the LED downlighter to load the board whilst I adjusted the output to 7v. I also checked that it stayed at 7v when the load was off.

Level Shifters

I tested the level shifters with a dual power supply and a multimeter. Three worked as expected but one did not. Rather than 7v / 0v, there was around 2v on the output. So I swapped out the FRB590 with a BC549 and it tested ok.

H-Bridge

The H-Bridge has been wired up and tested with the Furby's motor.

Edison

Thanks to gpolder and the pinout he found, soldering up the connections to the breakout board was straight forward.

Software

For the software side, the Furby needs to respond the events happening on the car. By subscribing to the same message queue as the car we can use pretty much the same code as for the car but just have different actions.

The previously developed MCU app communicates to the motor controller via the host control API and a bidirectional (or duplex) stream.

The duplex stream has "on" events for when data is recieved and a write method to send data.

var stream = require('stream');
var util = require('util');
var fileduplex = require('file-duplex');

var mcu = new fileduplex('/dev/ttymcu0');

mcu.on('data', function(data) {
    console.log('Data %s',data);
});

mcu.on('error', function(error) {  
    console.log('Error %s', error);
});

mcu.write("M"); //Request max value
mcu.write("C"); //Request counter value
//mcu.write("U"); //Count up
//mcu.write("D"); //Count down

Putting that together with the MRAA code from previous, we get the motor controller class for the Furby.

var mraa = require('mraa');

    var Motor = function (D1Pin, D2Pin, SpeedPin, HomePin, SensePin, mcuStream) {
    var self = this;

    self.MotorPin1 = new mraa.Gpio(D1Pin);
    self.MotorPin1.dir(mraa.DIR_OUT);
    self.MotorPin2 = new mraa.Gpio(D2Pin);
    self.MotorPin2.dir(mraa.DIR_OUT);
    self.MotorPinSpeed = new mraa.Pwm(SpeedPin);  //PWM available on default swizzler positions. (3,5,6,9)
    self.MotorPinSpeed.period_us(700);
    self.MotorPinSpeed.enable(true);
    self.mcu = mcuStream;
    self.positionDelta = 10;  //How many counter positions is close enough?
    self.counter = 0;
    self.max = 0;
    self.target = -1;    //What counter position to goto
    self.mcu.write("M"); //Ask the MCU to get the maximum value

    self.mcu.on('data', function(data) {
    switch (data.substring(0,1)) {
        case "C": {
            self.counter = data.substring(1);
            if (self.InPosition()) {
                console.log("Position found at %d", self.counter);
                self.Stop();
                self.target = -1;  
            }
            setTimeout(function() {self.mcu.write("C") },10);
            break;
        }
        case "M": {
            self.max = data.substring(1);
            break;
        }
        default:  
            console.log("Unexpected data recieved %s",data);
    }
    });

    self.mcu.on('error', function(error) {  
        console.log('Motor MCU error occurred %s', error);
    });

    self.Reset = function() {
        //Set the motor running for long enough to trigger a reset then stop
        var timeForOneRev = 1000;
        self.Forward();
        setTimeout(function() { self.Stop() },timeForOneRev);
        setTimeout(function() { self.mcu.write("C") },timeForOneRev);
    }

    self.Forward = function() {
        self.mcu.write("U");
        self.MotorPin1.write(1);
        self.MotorPin2.write(0);
    }

    self.Reverse = function() {
        self.mcu.write("D");
        self.MotorPin1.write(0);
        self.MotorPin2.write(1);
    }

    self.Stop = function() {
        self.target=-1;
        self.MotorPin1.write(0);
        self.MotorPin2.write(0);
    }

    self.Speed = function(percent) {
        self.MotorPinSpeed.write(percent);
    }

    self.Position = function() {
        return self.counter;
    }

    self.Max = function() {
        return self.max;
    }

    self.Distance = function(newPosition) {
        //What is the distance from the current position to the new position
        var p = self.Position();
        var m = self.Max();
        var D1 = newPosition - p;
        var D2 = (m - p) + newPosition;
        if (Math.abs(D1) < Math.abs(D2))
            return D1;
        else
            return D2;
    }

      self.Direction = function(newPosition) {
            return Math.sign(self.Distance(newPosition))
      }

      self.InPosition = function() {
          if (self.target == -1) return false; //Not going to a position
          return ((self.Distance() * self.Direction()) < self.positionDelta);
      }

      self.Goto = function(newPosition) {
            self.target = newPosition;
            if (self.InPosition()) {
                self.target=-1;
                return;
            }
            if (self.Direction(newPosition) > 0) {
                self.Forward();
            }
            else {
                self.Reverse();
            }
      }
};

    module.exports = Motor;

There's still a bit to be done with the software but I hope to have enough for a demo this weekend.

Reference

XL6009 DC-DC Converter Datasheet

How to create duplex streams with Node.js - a Nodejs programming tutorial for web developers | CodeWinds

https://nodejs.org/api/stream.html

https://www.npmjs.com/package/file-duplex

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