Раз такое дело))
uint32_t last_millis = 0;
uint8_t Print = 0;
const char * mass[] = {"Print_1", "Print_2", "Print_3"};
void setup() {
Serial.begin(9600);
}
void loop() {
if(millis() - last_millis >= 5000 )
{
last_millis = millis();
Serial.println(mass[Print++]);
if(Print > 2)
Print = 0;
}
}