Arduino Bluetooth Controlled Car Using HC-06 Module and MIT App Inventor

1/*
2FYI:  
3The data I transmit will be in this form @sum|leftSpeed|rightSpeed# my code removes the @ and # and 
4collects the data inside leaving us with sum|leftSpeed|rightSpeed, when i transmit the motor speeds via bluetooth i also transmit a sum, 
5eg if leftSped is 15 and rightSped is 113, then the sum is 1+5+1+1+3 = 11, if any of the data changes via transmission 
6then the transmitted sum won't correspond to the speed data sum and I will ignore the data.
7
8The data pieces eg sum and leftSpeed and rightSpeed are seperated by '|'.
9
10The left speed and right speeds i get from the bluetooth module which are sent from the phone have a range of 0 to 510, where 255 means stationary
11and 0 is full throttle backwards and 510 is full throttle forwards, you will see how I subtract 255 from my code later
12
13
14
15*/
16
17
18
19#include <AFMotor.h> //motor sheild library
20#include <math.h>
21
22
23AF_DCMotor M1(1);  //motor objects for each wheel
24AF_DCMotor M2(2);
25AF_DCMotor M3(3);
26AF_DCMotor M4(4);
27
28struct Speedies {   // this is a data structure which is convenient as i have a left side motor speed and a right side one.
29  float left;
30  float right;
31};
32
33
34int lSped = 0;      //some useful variables
35int rSped = 0;
36int sum = 0;   // the sum as mentioned above
37
38
39uint8_t hold1 = 0;     // I use these to find the locations of the '|' between the data pieces I send via bluetooth
40uint8_t hold2 = 0;
41
42
43
44//setting up bluetooth comms
45#include <SoftwareSerial.h>
46
47//rx and tx pins for communication between HC-O6 and arduino Mega
48const byte rxPin = 51;
49const byte txPin = 50;
50
51SoftwareSerial BTSerial(rxPin, txPin);
52
53
54
55
56//messaging keys
57const char START = '@';
58const char END = '#';
59
60const int TIMEOUT = 20; // this is the max length of the messagebuffer before I decide something is wrong and start listening for the start character again
61
62
63//messaging var
64String messageBuffer = "";
65bool waitingToStart = true; // waiting to recieve data as we recieved a start byte (for bluetooth comms)
66
67
68
69void setup() {
70  // put your setup code here, to run once:
71
72  pinMode(rxPin, INPUT);
73  pinMode(txPin, OUTPUT); //setting rx and tx pins in the right modes
74
75  //begin Serial comms
76  BTSerial.begin(9600);
77  Serial.begin(9600);
78}
79
80void loop() {
81  // put your main code here, to run repeatedly:
82
83
84                          // this bluetooth recieving section of the code is well explained in this bytes n bits video from time 13:50 (https://www.youtube.com/watch?v=jGoKdF8r7as), and I used it for this project
85  char nextData;
86
87  if (BTSerial.available()) {
88
89    if (waitingToStart) {
90
91      do {
92        nextData = BTSerial.read();
93      } while ((nextData != START) && BTSerial.available());
94      if (nextData == START) {
95        Serial.println("message starting");
96        waitingToStart = false;
97      }
98    }
99
100
101
102    if (!waitingToStart && BTSerial.available()) {
103
104      do {
105        nextData = BTSerial.read();
106        Serial.println(nextData);
107        messageBuffer += nextData;
108      } while ((nextData != END) && BTSerial.available());
109    }
110
111
112
113    if (nextData == END) {
114      messageBuffer = messageBuffer.substring(0, messageBuffer.length() - 1);
115      Serial.print("message complete ");
116      Serial.println(messageBuffer);
117
118      speedSet(extractInfo(messageBuffer));    //function to actually process bluetooth messageBuffer and then setMotor Speeds
119
120      
121
122
123
124      messageBuffer = "";
125      waitingToStart = true;
126    }
127
128    if (messageBuffer.length() > TIMEOUT) {
129      Serial.println("timeout error - " + messageBuffer);
130      messageBuffer = "";
131      waitingToStart = true;
132    }
133  }
134}
135
136
137
138
139int sumDigits(int n) {  // this is my function to add the digits in a number like 235 to get 2+3+5 = 10, which i use for error control
140  int sum = 0;
141  while (n > 0) {
142    sum += n % 10;
143    n = n / 10;
144  }
145  return sum;
146}
147
148
149
150
151Speedies extractInfo(String message) {  // this function extracts the info from the bluetooth data sent to first check if the data is valid then store it as some variables to send to the speedSet function
152
153  float lSpeed;
154  float rSpeed;
155
156  Speedies info;
157
158    hold1 = message.indexOf('|');
159    hold2 = message.lastIndexOf('|');
160
161    sum = message.substring(0, hold1).toInt();
162    lSped = message.substring((hold1+1), hold2).toInt();
163    rSped = message.substring((hold2+1), message.length()).toInt();
164
165
166  if(sum = (sumDigits(lSped) + sumDigits(rSped))){
167
168    info.left = lSped;
169    info.right = rSped;
170    return info;
171
172  } else{return;}
173
174
175
176  
177}
178
179
180void speedSet(Speedies speeda) {  // this function uses the extracted bluetooth info then sets the motor speeds
181
182  // i subtract 255 here so i can go from values of 0 tp 510 to -255 to 255, where a negative is backwards
183
184  float rightSpeed = speeda.left-255; //sorry about these two lines of code, they look weird but i just had my left motors swapped with my right ones
185
186  float leftSpeed = speeda.right-255;
187
188  if(leftSpeed < 70 && leftSpeed>-70){      //if the speeds are too low then i set the motor speed to 0 to avoid the motor sounds
189    leftSpeed = 0;
190  } else if(leftSpeed>255){
191    leftSpeed = 255;
192  } else if(leftSpeed<-255){   // setting max speed limits
193    leftSpeed = -255;
194  }
195
196  if(rightSpeed < 0 && rightSpeed>-70){
197    rightSpeed = 0;
198  } else if(rightSpeed>255){
199    rightSpeed = 255;
200  } else if(rightSpeed<-255){
201    rightSpeed = -255;
202  }
203
204
205
206    if (leftSpeed >= 0) {    // here i make negative speeds into backward
207
208      M2.run(FORWARD);
209      M3.run(FORWARD);
210      leftSpeed = leftSpeed;
211    } else {
212      M2.run(BACKWARD);
213      M3.run(BACKWARD);
214      leftSpeed = -1.0 * leftSpeed;
215    }
216
217    if (rightSpeed >= 0) {
218
219      M1.run(FORWARD);
220      M4.run(FORWARD);
221      rightSpeed = rightSpeed;
222    } else {
223      M1.run(BACKWARD);
224      M4.run(BACKWARD);
225      rightSpeed = -1.0 * rightSpeed;
226    }
227 
228    M2.setSpeed(round(leftSpeed));    //here i write to the motors and that's all!!!
229    M3.setSpeed(round(leftSpeed));
230
231    M1.setSpeed(round(rightSpeed));
232    M4.setSpeed(round(rightSpeed));
233
234
235}