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 create_uart_frame(uint8_t data, UART_Control *ctrl) {
    // Step 1: Ensure only 7-bit data
    data &= 0x7F;  

    // Step 2: If parity is disabled
    if (ctrl->parity_enable == 0) {
        return data;  // MSB will be 0 automatically since data is 7-bit
    }

    // Step 3: Count number of 1s in data
    int count = 0;
    uint8_t temp = data;
    while (temp) {
        count += (temp & 1);
        temp >>= 1;
    }

    // Step 4: Compute parity bit
    uint8_t parity_bit;
    if (ctrl->parity_type == 0) {  
        // Even parity
        parity_bit = (count % 2 == 0) ? 0 : 1;
    } else {  
        // Odd parity
        parity_bit = (count % 2 == 0) ? 1 : 0;
    }

    // Step 5: Construct frame (parity in MSB + data in lower 7 bits)
    return (parity_bit << 7) | 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