Using the Arduino to replace chip logic

Doug and Kay of submarineboat.com have created a control circuit to drive their ROV. They use chip logic to map joystick inputs to motor output. They use two motors positioned left & right of the vehicle center line. Motion is achieved by selectively powering the motors singularly or in pairs, forward or reverse to achieve the desired effect. Forward - both motors fire forward, rotating - one fires forward, one fires aft, moving and turning - one motor fires while asymmetric thrust and drag achieves the desired action. Here we use an Arduino and software logic to replace their chip logic.

Link to their original design.

The code:

/*

ROV Controller Proof of Concept, created by Stephan, 20100306-01

*/

// map the inputs

#define JA 12

#define JB 9

#define JC 6

#define JD 4

// map the outputs

#define LED_LF 13

#define LED_LR 10

#define LED_RF 7

#define LED_RR 5

bool nand(bool A, bool B);

bool nand(bool A, bool B, bool C);

void logic_circuit (bool A, bool B, bool C, bool D, bool &LF, bool &LR, bool &RF, bool &RR);

int a,b,c,d;

bool LF,LR,RF,RR;

bool A = true;

bool B = true;

bool C = true;

bool D = true;

void setup() {

// setup the input pins

pinMode(JA, INPUT);

pinMode(JB, INPUT);

pinMode(JC, INPUT);

pinMode(JD, INPUT);

// assign the LED pin as an output

pinMode(LED_LF, OUTPUT);

pinMode(LED_LR, OUTPUT);

pinMode(LED_RF, OUTPUT);

pinMode(LED_RR, OUTPUT);

}

void loop() {

// read the joystick

a = (digitalRead(JA));

b = (digitalRead(JB));

c = (digitalRead(JC));

d = (digitalRead(JD));

// abstract the joystick readings

A = (a == HIGH) ? true : false;

B = (b == HIGH) ? true : false;

C = (c == HIGH) ? true : false;

D = (d == HIGH) ? true : false;

// run the logic circuit

logic_circuit(A,B,C,D,LF,LR,RF,RR);

// write to output

digitalWrite(LED_LF, LF);

digitalWrite(LED_LR, LR);

digitalWrite(LED_RF, RF);

digitalWrite(LED_RR, RR);

}

void logic_circuit (bool A, bool B, bool C, bool D, bool &LF, bool &LR, bool &RF, bool &RR) {

/*

This subroutine simulates a logic circuit created by Doug & Kay (SVSeeker@ymail.com).

The circuit was created to accept switched based joystick inputs and deliver logic signals

to activate power relays to drive a submerged ROV, according to a defined truth table.

Reference:

http://www.submarineboat.com/rov_joystick_for_props.htm#DC_Motors

Truth Table

Input from Joystick switch Output to Relay

A B C D LF LR RF RR

0 0 0 1 1 1

0 0 1 0 1 1

0 0 1 1 1

0 1 0 0 1 1

0 1 1 0 1

1 0 0 0 1 1

1 0 0 1 1

1 1 0 0 1

*/

// Left Forward

LF = nand(nand(A,!C,!D), nand(B,!C,!D));

// Right Forward

RF = nand(nand(!B,!C,D), nand(A,!B,!C));

// Left Reverse

LR = nand(nand(!A,!B,C), nand(!A,!B,D));

// Right Reverse

RR = nand(nand(!A,C,!D), nand(!A,B,!D));

}

/*

Two functions are provided to simulate the behavior of dual-input and triple-input NAND gates.

The function is overloaded based on the number of inputs two or three.

The functions accept bools as inputs and returns a bool.

The NAND gate is simulated using the ternary operator. If the operator evaluates to true,

it returns false and vice versa.

*/

bool nand (bool A, bool B) {

bool result = (A && B) ? false : true;

return (result);

}

bool nand (bool A, bool B, bool C) {

bool result = (A && B && C) ? false : true;

return (result);

}