Transmitter – Prototype Code Explanation

This is an explanation of the code I developed for the transmitter part of the project. Although it’s already heavily commented, I hope I can explain as clearly and fully as possible what I am trying to achieve and the reasons for the choices and decisions I have made in the code.

/*
RC Information Board Project

This project reads in RC car race information output from RC-Timing by Dale Burr
(race information such as heat number, round number, time elapsed etc) and also
gantry/start lights information.

Race information is read in via the normal Arduino serial port (USB on an Uno
or pins 0 and 1 on an Uno or Atmega 328P-Pu IC) whilst gantry/start lights
information is read in via 2 Arduino pins after having been converted from RS232
by a MAX232 or similar.

The Arduino then processes the information and transforms it into 7 seperate
integer variables which are then joined using the sprintf function and
transmitted using the VirtualWire library from a 433Mhz MX-FS-03V transmitter
connected to the Arduino

For more information on this project, visit:

https://rcinfoboard.wordpress.com/

Created by Joe Keaveney
February 2016
*/

#include // Library required for LCD 16×2 display for testing
#include // Library required for data transmission over 433Mhz

LiquidCrystal lcd(12, 9, 5, 4, 3, 2); // tell Arduino the LCD pin configuration

char tx_array[20]; // The array of variables that is transmitted
char inputChar[50]; // The string (char array) that we search through for data
char *i;
char *rnum; // round number character
char *hnum; // heat number character
char *mnum; // etc
char *snum; // etc
int lstate = 0; // start/gantry lights state integer
int r_int; // round number integer
int h_int; // etc
int m_int; // etc
int s_int; // etc
int timeone; //integer that represents the first number of a 4-digit display
int timetwo; // second number
int timethree; // third number
int timefour; // fourth number

const int dtrPin = 6; // DTR input pin from MAX232/USB
const int rtsPin = 7; // RTS input pin from MAX232/USB
int dtrState = 0; // stores the state of DTR pin when read
int rtsState = 0; // stores the state of RTS pin when read

String inputString = “”; // a string to hold incoming data
boolean stringComplete = false; // whether the string is complete

void setup() { // setup Arduino in it’s initial state & start services
pinMode(dtrPin, INPUT); // set input pins for reading RS232 pin states
pinMode(rtsPin, INPUT);
lcd.begin(16, 2); // initialize LCD display and tell Arduino how big it is
Serial.begin(9600); // initialize serial so we can read in race information
inputString.reserve(200); // reserve 200 bytes for the inputString:
vw_set_ptt_inverted(true); // setup 433Mhz hardware – need this for MX-FS-03V
vw_set_tx_pin(8); // set Tx pin number
vw_setup(2000);// speed of data transfer Kbps – 2000 is fine & stable
}

void loop() {

dtrState = digitalRead(dtrPin); // read the state of the DTR and RTS inputs
rtsState = digitalRead(rtsPin);
//dtrState = !dtrState ; // Inverts the inputs, necessary due to TTL conversion
//rtsState = !rtsState ;

if (dtrState == LOW && rtsState == LOW) {
// DTR HIGH and RTS HIGH mean Green Light On
lstate = 2;
} else if (dtrState == LOW && rtsState == HIGH) {
// DTR HIGH and RTS LOW means Red Light On
lstate = 1;
}
else {
// Any other combination means both lights Off
lstate = 0;
}

if (stringComplete) {
inputString.toCharArray(inputChar, 50); // convert the input string to char
rnum = strtok_r(inputChar,”:”,&i); // start breaking down the input info
hnum = strtok_r(NULL,”:”,&i); // from RC-Timing into the data we need
mnum = strtok_r(NULL,”:”,&i);
snum = strtok_r(NULL,”:”,&i);
r_int = atoi(rnum); // convert the info into integers
h_int = atoi(hnum);
m_int = atoi(mnum);
s_int = atoi(snum);
if (m_int <= 9) { // break the time info into two integers for use on a
timeone = 0; // 4-digit display
timetwo = m_int;
// lcd.print(timeone);
// lcd.print(timetwo);
}
else {
timeone = m_int / 10;
timetwo = m_int % 10;
// lcd.print(timeone);
// lcd.print(timetwo);
}
// lcd.print(“:”);
if (s_int <= 9) {
timethree = 0;
timefour = s_int;
// lcd.print(timethree);
// lcd.print(timefour);
}
else {
timethree = s_int / 10;
timefour = s_int % 10;
// lcd.print(timethree);
// lcd.print(timefour);
}

lcd.clear(); //this section output the data to an LCD display
lcd.print(“R:”); //in the finished device, this will be removed
lcd.print(r_int);
lcd.print(” H:”);
lcd.print(h_int);
lcd.setCursor(4,1);
lcd.print(“TIME:”);
lcd.print(timeone);
lcd.print(timetwo);
lcd.print(“:”);
lcd.print(timethree);
lcd.print(timefour);

inputString = “”; // clear the string and flag ready to listen again
stringComplete = false;
}
// the sprintf function consolidates all the integer variables together
// and then vw_send and vw_wait send the info out on the 433Mhz Tx
sprintf(tx_array, “%d,%d,%d,%d,%d,%d,%d.”,lstate,r_int,h_int,timeone,timetwo,timethree,timefour);
vw_send((uint8_t*)tx_array, strlen(tx_array));
vw_wait_tx();
}

/*
SerialEvent occurs whenever a new data comes in the
hardware serial RX (USB or Arduino pins 0 and 1).
This routine is run between each
time loop() runs.
*/
void serialEvent() { // function declaration
while (Serial.available()) { // is there data to be processed?
char inChar = (char)Serial.read(); // get the new byte
if (inChar != ‘[‘ && inChar != ‘]’) { // filter out the [ and ] brackets
inputString += inChar; // add it to the inputString:
}
// if the incoming character is ‘]’ (ie end of message from RC-Timing),
// set a flag so the main loop can do something about it:
if (inChar == ‘]’) {
stringComplete = true;
}
}
}