try sending buffer

serialtimetest/serialtimetest.c

@@ -21,8 +21,11 @@
 int speed,port;
 unsigned char msg0 = 0;
 unsigned char msg1 = 255;
+unsigned char buf[4] = {0,100,200,255};
 //
 void timer_handler (int signum) {
+   write(port,&buf,4);
+   /*
    static int flag = 0;
    if (flag == 0) {
       flag = 1;
@@ -32,6 +35,7 @@ void timer_handler (int signum) {
       flag = 0;
       write(port,&msg1,1);
       }
+   */
    }
 //
 int main(int argc,char *argv[]) {