For this project we use the Feather M0 Bluefruit and write the code in C/C++ using the Arduino framework and tools. This board was selected for it's Bluetooth capabilities, which will let us drive the robot using the Adafruit Bluefruit app controller interface, as well as run pre-written sequences using the controller's 1-4 buttons.

You'll need to have the Arduino IDE installed as well as the appropriate board packages and libraries. The Feather M0 Bluefruit LE guide covers this in detail. It's a good idea to read through that guide if you haven't yet; it will show you all the tricks of this board.

This code has a couple support files with it that were copied from the controller.ino example: BluefruitConfig.h and packetParser.cpp. Either start a new sketch called FlippyBot and copy them into the directory along with the FlippyBot.ino file below, or clone the repo from GitHub; it has everything in place that's needed.  In either case, load FlippyBot into the Arduino IDE, set your board and port (see the linked guide for this Feather board), and compile/upload the code.

We won't go into detail on the boilerplate BLE setup and use. That's covered in the linked guide and the comments from the example code that was used have been kept intact.

We start by creating motor objects, and placing them in an array. We define a constant index for each leg. Additionally there is an array of strings used in debug output for leg names.

Adafruit_Crickit crickit;
seesaw_Motor right_leg(&crickit);
seesaw_Motor left_leg(&crickit);

seesaw_Motor *legs[2] = {&right_leg, &left_leg};
const __FlashStringHelper *leg_names[] = {F("right"), F("left")};

const int RIGHT = 0;
const int LEFT = 1;

Speaking of debugging, there are two small functions for outputting errors and information. If you want to output to the serial console simply uncomment the #define DEBUG line near the start of the file. Remember to recompile/upload with it commented out before running the robot untethered.

void error(const __FlashStringHelper *err)
{
  digitalWrite(13, HIGH);
#ifdef DEBUG
  Serial.println(err);
#endif
  while (1);
}

void log(const __FlashStringHelper *msg)
{
#ifdef DEBUG
  Serial.println(msg);
#endif
}

To encapsulate everything needed to set the velocity of a leg motor, we have the set_leg function. It checks the validity of the arguments, prints debugging information if DEBUG is defined, and sets the velocity of the leg.

void set_leg(int leg, float velocity)
{
  if (leg != RIGHT && leg != LEFT) {
    error(F("Bad leg specifier"));
  }
  if (velocity < -1.0 || velocity > 1.0) {
    error(F("Velocity out of -1.0//1.0 range"));
  }

#ifdef DEBUG
  Serial.print(F("Setting "));
  Serial.print(leg_names[leg]);
  Serial.print(F(" to "));
  Serial.println(velocity);
#endif

  legs[leg]->throttle(velocity);
}

Note that the parameter here is called velocity, whereas in the next set of functions, the corresponding parameter is speed.  Speed is just how fast something is going. In our case it's always positive and specifies how fast to spin the drive shaft (0.0 being stopped, and 1.0 being full speed). Velocity also contains a direction. With respect to a motor that's simply forward or reverse and is indicated by the sign of the value: positive for forward and negative for reverse.

These next functions control motion of the bot, manipulating the speed and direction of the two motors. Remember that if a motor is spinning in the opposite direction than it should, simply switch its connections to the CRICKIT motor driver.

void stop()
{
  set_leg(RIGHT, 0.0);
  set_leg(LEFT, 0.0);
}

void forward(float speed)
{
  set_leg(RIGHT, speed);
  set_leg(LEFT, speed);
}

void reverse(float speed)
{
  set_leg(RIGHT, speed * -1);
  set_leg(LEFT, speed * -1);
}

void rotate_clockwise(float speed)
{
  set_leg(RIGHT, speed * -1);
  set_leg(LEFT, speed);
}

void rotate_counterclockwise(float speed)
{
  set_leg(RIGHT, speed);
  set_leg(LEFT, speed * -1);
}

The setup function is primarily boilerplate configuration and initialization of the bluetooth stack. The last bit is relevant to the bot, though: initializing the CRICKIT and connecting the motor objects to the motor drivers.

if (!crickit.begin()) {
  error(F("Error initializing CRICKIT!"));
}
log(F("Crickit started"));

right_leg.attach(CRICKIT_MOTOR_A1, CRICKIT_MOTOR_A2);
left_leg.attach(CRICKIT_MOTOR_B1, CRICKIT_MOTOR_B2);

Since the design goal is to control the bot from the Bluefruit phone app, there are four slots for predefined scripts that get triggered by the 1-4 buttons. The first one has been filled in as an example.

void demo1()
{
  forward(1.0);
  delay(5000);
  rotate_clockwise(1.0);
  delay(2000);
  forward(0.75);
  delay(4000);
  rotate_counterclockwise(1.0);
  delay(3000);
  stop();
}

void demo2()
{
}

void demo3()
{
}

void demo4()
{
}

The main loop checks for a command from the controller via Bluetooth and moves the bot as requested.

void loop()
{
  // Wait for new data to arrive
  uint8_t len = readPacket(&ble, BLE_READPACKET_TIMEOUT);
  if (len == 0) return;

  // Got a packet!
  // printHex(packetbuffer, len);

   // Buttons
  if (packetbuffer[1] == 'B') {
    uint8_t buttnum = packetbuffer[2] - '0';
    boolean pressed = packetbuffer[3] - '0';

#ifdef DEBUG
    Serial.print ("Button "); Serial.print(buttnum);
    if (pressed) {
      Serial.println(" pressed");
    } else {
      Serial.println(" released");
    }
#endif
    switch(buttnum) {
    case 1:
      if (pressed) {
        demo1();
      }
      break;
    case 2:
      if (pressed) {
        demo2();
      }
      break;
    case 3:
      if (pressed) {
        demo3();
      }
      break;
    case 4:
      if (pressed) {
        demo4();
      }
      break;
    case 5:
      if (pressed) {
        forward(1.0);
      } else {
        stop();
      }
      break;
    case 6:
      if (pressed) {
        reverse(1.0);
      } else {
        stop();
      }
      break;
    case 7:
      if (pressed) {
        rotate_counterclockwise(1.0);
      } else {
        stop();
      }
      break;
    case 8:
      if (pressed) {
        rotate_clockwise(1.0);
      } else {
        stop();
      }
      break;
    }
  }
}

In case you haven't run into the switch statement before, it chooses a case block based on the value given to it, buttnum in this case.  The case block with the corresponding value is executed.  Notice that each case block ends with a break statement.  This exits the switch. If they weren't there, the next case block would be executed, and so on until the end of the switch was reached or a break statement was encountered.

The entire FilppyBot.ino source file is below.

// Triangular leg robot.

// Bluetooth code is from Feather M0 Bluefruit controller example.
// Explainatory comments kept intact.

// Adafruit invests time and resources providing this open source code.
// Please support Adafruit and open source hardware by purchasing
// products from Adafruit!

// Written by Dave Astels for Adafruit Industries
// Copyright (c) 2018 Adafruit Industries
// Licensed under the MIT license.

// All text above must be included in any redistribution.

#include <stdarg.h>
#include <string.h>
#include <Arduino.h>
#include <SPI.h>
#include "Adafruit_BLE.h"
#include "Adafruit_BluefruitLE_SPI.h"
#include "Adafruit_BluefruitLE_UART.h"

#include "BluefruitConfig.h"

#include "Adafruit_Crickit.h"
#include "seesaw_motor.h"

#define FACTORYRESET_ENABLE         1
#define MINIMUM_FIRMWARE_VERSION    "0.6.6"
#define MODE_LED_BEHAVIOUR          "MODE"

// function prototypes over in packetparser.cpp
uint8_t readPacket(Adafruit_BLE *ble, uint16_t timeout);
float parsefloat(uint8_t *buffer);
void printHex(const uint8_t * data, const uint32_t numBytes);

// the packet buffer
extern uint8_t packetbuffer[];

//#define DEBUG 1


Adafruit_BluefruitLE_SPI ble(BLUEFRUIT_SPI_CS, BLUEFRUIT_SPI_IRQ, BLUEFRUIT_SPI_RST);


//------------------------------------------------------------------------------
// setup crickit & motors

Adafruit_Crickit crickit;
seesaw_Motor right_leg(&crickit);
seesaw_Motor left_leg(&crickit);

seesaw_Motor *legs[2] = {&right_leg, &left_leg};
const __FlashStringHelper *leg_names[] = {F("right"), F("left")};

const int RIGHT = 0;
const int LEFT = 1;

//------------------------------------------------------------------------------
// conditional output routines

void error(const __FlashStringHelper *err)
{
  digitalWrite(13, HIGH);
#ifdef DEBUG
  Serial.println(err);
#endif
  while (1);
}


void log(const __FlashStringHelper *msg)
{
#ifdef DEBUG
  Serial.println(msg);
#endif
}



void set_leg(int leg, float velocity)
{
  if (leg != RIGHT && leg != LEFT) {
    error(F("Bad leg specifier"));
  }
  if (velocity < -1.0 || velocity > 1.0) {
    error(F("Velocity out of -1.0//1.0 range"));
  }

#ifdef DEBUG
  Serial.print(F("Setting "));
  Serial.print(leg_names[leg]);
  Serial.print(F(" to "));
  Serial.println(velocity);
#endif

  legs[leg]->throttle(velocity);
}


void stop()
{
  set_leg(RIGHT, 0.0);
  set_leg(LEFT, 0.0);
}


void forward(float speed)
{
  set_leg(RIGHT, speed);
  set_leg(LEFT, speed);
}


void reverse(float speed)
{
  set_leg(RIGHT, speed * -1);
  set_leg(LEFT, speed * -1);
}


void rotate_clockwise(float speed)
{
  set_leg(RIGHT, speed * -1);
  set_leg(LEFT, speed);
}


void rotate_counterclockwise(float speed)
{
  set_leg(RIGHT, speed);
  set_leg(LEFT, speed * -1);
}


void initialize()
{
  stop();
}


//------------------------------------------------------------------------------
// Start things up

void setup()
{
  pinMode(13, OUTPUT);
  digitalWrite(13, LOW);

#ifdef DEBUG
  while (!Serial);  // required for Flora & Micro
  delay(500);
  Serial.begin(115200);
#endif

  log(F("FlippyBot"));
  log(F("-----------------------------------------"));

  // Initialise the module
  log(F("Initialising the Bluefruit LE module: "));

  if ( !ble.begin(VERBOSE_MODE) )
  {
    error(F("Couldn't find Bluefruit, make sure it's in CoMmanD mode & check wiring?"));
  }

  log( F("OK!") );

  if ( FACTORYRESET_ENABLE )
  {
    // Perform a factory reset to make sure everything is in a known state
    log(F("Performing a factory reset: "));
    if ( ! ble.factoryReset() ){
      error(F("Couldn't factory reset"));
    }
  }

   // Disable command echo from Bluefruit
  ble.echo(false);

  log(F("Requesting Bluefruit info:"));
  // Print Bluefruit information
  ble.info();

  log(F("Please use Adafruit Bluefruit LE app to connect in Controller mode"));
  log(F("Then activate/use the sensors, color picker, game controller, etc!\n"));

  ble.verbose(false);  // debug info is a little annoying after this point!

  // Wait for connection
  while (! ble.isConnected()) {
      delay(500);
  }

  log(F("******************************"));

  // LED Activity command is only supported from 0.6.6
  if ( ble.isVersionAtLeast(MINIMUM_FIRMWARE_VERSION) )
  {
    // Change Mode LED Activity
    log(F("Change LED activity to " MODE_LED_BEHAVIOUR));
    ble.sendCommandCheckOK("AT+HWModeLED=" MODE_LED_BEHAVIOUR);
  }

  // Set Bluefruit to DATA mode
  log( F("Switching to DATA mode!") );
  ble.setMode(BLUEFRUIT_MODE_DATA);

  log(F("******************************"));

  if (!crickit.begin()) {
    error(F("Error initializing CRICKIT!"));
  }
  log(F("Crickit started"));

  right_leg.attach(CRICKIT_MOTOR_A1, CRICKIT_MOTOR_A2);
  left_leg.attach(CRICKIT_MOTOR_B1, CRICKIT_MOTOR_B2);
}


// Fill these functions in with the movement scripts you want attached to
// the controller's 1-4 buttons

void demo1()
{
  forward(1.0);
  delay(5000);
  rotate_clockwise(1.0);
  delay(2000);
  forward(0.75);
  delay(4000);
  rotate_counterclockwise(1.0);
  delay(3000);
  stop();
}


void demo2()
{
}


void demo3()
{
}


void demo4()
{
}


//------------------------------------------------------------------------------
// Main loop

void loop()
{
  // Wait for new data to arrive
  uint8_t len = readPacket(&ble, BLE_READPACKET_TIMEOUT);
  if (len == 0) return;

  // Got a packet!
  // printHex(packetbuffer, len);

   // Buttons
  if (packetbuffer[1] == 'B') {
    uint8_t buttnum = packetbuffer[2] - '0';
    boolean pressed = packetbuffer[3] - '0';

#ifdef DEBUG
    Serial.print ("Button "); Serial.print(buttnum);
    if (pressed) {
      Serial.println(" pressed");
    } else {
      Serial.println(" released");
    }
#endif
    switch(buttnum) {
    case 1:
      if (pressed) {
        demo1();
      }
      break;
    case 2:
      if (pressed) {
        demo2();
      }
      break;
    case 3:
      if (pressed) {
        demo3();
      }
      break;
    case 4:
      if (pressed) {
        demo4();
      }
      break;
    case 5:
      if (pressed) {
        forward(1.0);
      } else {
        stop();
      }
      break;
    case 6:
      if (pressed) {
        reverse(1.0);
      } else {
        stop();
      }
      break;
    case 7:
      if (pressed) {
        rotate_counterclockwise(1.0);
      } else {
        stop();
      }
      break;
    case 8:
      if (pressed) {
        rotate_clockwise(1.0);
      } else {
        stop();
      }
      break;
    }
  }
}

This guide was first published on Oct 17, 2018. It was last updated on Oct 17, 2018.

This page (Code) was last updated on Sep 23, 2020.

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