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;

uint8_t sum_7bits (uint8_t data) {
    uint8_t i, result=0;
    for (i=0; i<7; i++) {
        result ^= (data & 0x1);
        data = data >> 1;
    }
    return result;
}
uint8_t create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Your logic here
    uint8_t result;
    uint8_t parity_bit, sum;

    result = data;
    if (ctrl->parity_enable == 0) {
        return result;
    }

    sum = sum_7bits(data);
    switch (ctrl->parity_type) {
        case 0:
        // even parity
        result = (sum == 0 ? result: (result ^ 0x80));
        return result;

        case 1:
        default:
        result = (sum == 0 ? (result ^ 0x80) : result);
        return result;
    }
}

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

create a routine to count bits then set parity if required