update

uart_read_test_main.cpp

@@ -68,7 +68,7 @@ int main(int argc, char *argv[]) {
     int ret1, ret2;
     ret1 = uartReceive(&dev, buf, 2 /*接收的字节数2-1*/);  // send the received text over UART
     if (ret1 != 0) {
-      printf("%x", buf[0]);
+      printf("0x%02x", buf[0]);
       i++;
       if (i % 20 == 0) {
         printf("\n");