Construct UART Data Frame with Parity Bit

Code

#include <stdio.h>
#include <stdint.h>

typedef struct {
    uint8_t parity_enable : 1;
    uint8_t parity_type   : 1;
    uint8_t reserved      : 6;
} UART_Control;

int count_ones (uint8_t data)
{
    int count = 0 ;
    for (int i=0 ; i<7 ;i++)
    {
        if(data & (1 << i))
        {
            count++;
        }
        
    }
    return count;
}



uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Your logic here
    data = data & 0x7F;  // Ensure 7-bit data

    if (ctrl->parity_enable == 0) {
        return data;  // No parity, MSB is 0
    }

    int ones = count_ones(data);
    int parity_bit;

    if (ctrl->parity_type == 0) {
        // Even parity: parity bit is 1 if ones are odd
        parity_bit = (ones % 2 == 0) ? 0 : 1;
    } else {
        // Odd parity: parity bit is 1 if ones are even
        parity_bit = (ones % 2 == 0) ? 1 : 0;
    }

    return (parity_bit << 7) | data;  // Frame = parity_bit at MSB + data

}



// int count_ones(uint8_t data) {
//     int count = 0;
//     for (int i = 0; i < 7; i++) {
//         if (data & (1 << i)) {
//             count++;
//         }
//     }
//     return count;
// }

// // Construct UART frame based on control register settings
// uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
//     data = data & 0x7F;  // Ensure 7-bit data

//     if (ctrl->parity_enable == 0) {
//         return data;  // No parity, MSB is 0
//     }

//     int ones = count_ones(data);
//     int parity_bit;

//     if (ctrl->parity_type == 0) {
//         // Even parity: parity bit is 1 if ones are odd
//         parity_bit = (ones % 2 == 0) ? 0 : 1;
//     } else {
//         // Odd parity: parity bit is 1 if ones are even
//         parity_bit = (ones % 2 == 0) ? 1 : 0;
//     }

//     return (parity_bit << 7) | data;  // Frame = parity_bit at MSB + data
// }

int main() {
    uint8_t data;
    scanf("%hhu", &data);  // 7-bit input

    uint8_t parity_enable, parity_type;
    scanf("%hhu %hhu", &parity_enable, &parity_type);

    UART_Control ctrl;
    ctrl.parity_enable = parity_enable;
    ctrl.parity_type = parity_type;

    uint8_t frame = create_uart_frame(data, &ctrl);
    printf("frame = 0x%02X", frame);

    return 0;
}

Solving Approach