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hans00/low_delay_3ping.ino

Last active March 30, 2017 09:18
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low_delay_3ping.ino
// 優化效率
#define ddtick __asm__("nop\n\t")
#if F_CPU == 20000000L
#define dd5tick __asm__("nop\n\t""nop\n\t""nop\n\t""nop\n\t""nop\n\t")
#define delayOneUs() { dd5tick; dd5tick; dd5tick; dd5tick; }
#endif
#if F_CPU == 16000000L
#define dd4tick __asm__("nop\n\t""nop\n\t""nop\n\t""nop\n\t")
#define delayOneUs() { dd4tick; dd4tick; dd4tick; dd4tick; }
#endif
#define delay2Us() { delayOneUs(); delayOneUs(); }
#define delay5Us() { delay2Us(); delay2Us(); delayOneUs(); }
int ping() {
pinMode(PING_PIN, OUTPUT);
digitalWrite(PING_PIN, LOW); delay2Us();
digitalWrite(PING_PIN, HIGH); delay5Us();
digitalWrite(PING_PIN, LOW);
pinMode(PING_PIN, INPUT);
return pulseIn(PING_PIN, HIGH) / 29 / 2;
}
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