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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) {
    
    data &= 0x7F;
    uint8_t frame = data;
    if(ctrl->parity_enable == 0) {
        frame &= ~(1U << 7);
    }else {
        int count = 0;
        for(int i = 0; i < 7; i++) {
            if((data >> i) & 1)
                count++;
        }
        if(ctrl->parity_type == 0) {
            if(count % 2 == 0) 
                frame &= (1U << 7) - 1;
            else
                frame |= 1U << 7;
        }else {
            if(count % 2 == 0)
                frame |= 1U << 7;
            else
                frame &= (1U << 7) - 1;
        }
    }

    return frame;
}

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

 

 

 

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Input

85 1 0

Expected Output

frame = 0x55