#include <stdio.h>
#include <fcntl.h>
#include <errno.h>

main () {
    unsigned char a[40];
    unsigned char c;
    int i = 0;
    int j;
    unsigned char sum = 0;
	int fd,ret;

	fd = open("/dev/cua1",O_RDWR);
	printf("fd = %d\n",fd);

    a[i++] = 0xAA;
    a[i++] = 0x00;
    a[i++] = 0x13;
    a[i++] = 0x20;

	sum = 0;
    for(j=1;j<i;j++) sum += a[j];
    a[i] = sum & 0xFF;

    for(j=0;j<=i;j++) {
		ret = write(fd,&a[j],1);
		if(ret != 1) {
			printf("write returned %d errno = %d\n",ret,errno);
			perror("Write: ");
		}
	}

	printf("About to read...\n");
	while(1) {
		ret = read(fd,&c,1);
		printf("read returned %d character = 0x%x (%c)\n",ret,c,c);
	}
}