Implementing Full Subtractor using VSDSquadron Mini

  • VSDSquadron Mini board
  • Push Buttons
  • 2 LEDs
  • Breadboard
  • Jumper Wires
  • VS Code , Platformio


D = (A XOR B) XOR Bin

= A’B’Bin + A’BBin’ + AB’Bin’ + ABBin
= Bin(A’B’ + AB)  + Bin’(AB’ + A’B)  
= Bin( A XNOR B) + Bin’(A XOR B)  
= Bin (A XOR B)’  +  Bin’(A XOR B)
= Bin XOR (A XOR B)
= (A XOR B) XOR Bin

Bout= A’Bin + A’B + BBin

 = A’B’Bin + A’BBin’ + A’BBin + ABBin      
 = A’B’Bin +A’BBin’ + A’BBin + A’BBin + A’BBin + ABBin
 = A’Bin(B + B’) + A’B(Bin + Bin’) + BBin(A + A’)
 = A’Bin + A’B + BBin

VSDSquadron Mini BoardHardware Connections
GNDLED1 anode, LED2 anode, Switch(1,2,3) anode
PD1Switch 1 cathode (A)
PD2Switch 2 cathode (B)
PD3Switch 3 cathode (Bin)
PC4Red LED (Borrow)
PC5Green LED (Difference)

// Full Subtractor Implementation

// Included the required header files
#include <stdio.h>
#include <debug.h>
#include <ch32v00x.h>

// Defining the Logic Gate Functions
int and(int bit1, int bit2)
{
    int out = bit1 & bit2;
    return out;
}
int or(int bit1, int bit2)
{
    int out = bit1 | bit2;
    return out;
}
int xor(int bit1, int bit2)
{
    int out = bit1 ^ bit2;
    return out;
}
int not(int bit)
{
    int out = ~bit & 1; // Ensuring only the least significant bit is considered
    return out;
}

// Configuring GPIO Pins
void GPIO_Config(void)
{
    GPIO_InitTypeDef GPIO_InitStructure = {0}; // structure variable used for GPIO configuration
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOD, ENABLE); // to enable the clock for port D
    RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC, ENABLE); // to enable the clock for port C
    
    // Input Pins Configuration
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_1 | GPIO_Pin_2 | GPIO_Pin_3;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IPU; // Defined as Input Type with pull-up
    GPIO_Init(GPIOD, &GPIO_InitStructure);

    // Output Pins Configuration
    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4 | GPIO_Pin_5;
    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_Out_PP; // Defined Output Type
    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz; // Defined Speed
    GPIO_Init(GPIOC, &GPIO_InitStructure);
}

// The MAIN function responsible for the execution of the program
int main()
{
    uint8_t A, B, Bin, Diff, Bout; // Declared the required variables
    uint8_t p, q, r; 
    NVIC_PriorityGroupConfig(NVIC_PriorityGroup_2);
    SystemCoreClockUpdate();
    Delay_Init();
    GPIO_Config();

    while(1)
    {
        A = GPIO_ReadInputDataBit(GPIOD, GPIO_Pin_1);
        B = GPIO_ReadInputDataBit(GPIOD, GPIO_Pin_2);
        Bin = GPIO_ReadInputDataBit(GPIOD, GPIO_Pin_3);
        
        // Full Subtractor Logic
        Diff = xor(xor(A, B), Bin); // Difference = A ⊕ B ⊕ Bin
        p = and(not(A), B); // p = A' B
        q = and(B, Bin); // q = B Bin
        r = and(not(A), Bin); // r = A' Bin
        Bout = or(or(p, q), r); // Borrow out = A' B + B Bin + A' Bin

        // Write the Difference output
        if(Diff == 1)
        {
            GPIO_WriteBit(GPIOC, GPIO_Pin_4, RESET); // LED on for Difference = 1
        }
        else
        {
            GPIO_WriteBit(GPIOC, GPIO_Pin_4, SET); // LED off for Difference = 0
        }

        // Write the Borrow output
        if(Bout == 1)
        {
            GPIO_WriteBit(GPIOC, GPIO_Pin_5, RESET); // LED on for Borrow out = 1
        }
        else
        {
            GPIO_WriteBit(GPIOC, GPIO_Pin_5, SET); // LED off for Borrow out = 0
        }
    }
}
                                                                                              

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