我有一个带有 AlphaBot2 的树莓派零,它具有 HC-SR04 超声波传感器。使用 Python 的实现效果很好。我想在 C 中实现,因为我需要将它与另一个也在 C 中的程序绑定并且出于优化的原因。我注意到的第一件事是 Python 代码使用了 RPi.GPIO 库,而在 CI 中必须使用wiringPi 或bcm2835。所以我决定使用wiringPi lib。我的程序执行但距离不正确。与我在 web 上找到的实现不同的一件事是我使用的是 TRIG 22 和 ECHO 27,因为我的 HC-SR04 连接到 AlphaBot2。我没有使用 2 个电阻将其连接到树莓派。当我在传感器前面放置一些障碍物时,即使将其移动到 30 厘米,我也只能得到 3 和 5 厘米。
Distance: 3905724cm
Distance: 5cm
Distance: 5cm
Distance: 5cm
Distance: 5cm
Distance: 3cm
Distance: 3cm
Distance: 5cm
Distance: 5cm
这是我的代码:
#include <stdio.h>
#include <stdlib.h>
#include <wiringPi.h>
#include "ultrasonicClient.h"
#define TRUE (1==1)
// HC-SR04 ultrasonic sensor on AlphaBot2 Pi Zero
#define TRIG 22
#define ECHO 27
static volatile long startTimeUsec;
static volatile long endTimeUsec;
double speedOfSoundMetersPerSecond = 340.29;
void recordPulseLength() {
startTimeUsec = micros();
while (digitalRead(ECHO) == HIGH);
endTimeUsec = micros();
}
void setupUltrasonic() {
wiringPiSetup();
pinMode(TRIG, OUTPUT);
pinMode(ECHO, INPUT);
// TRIG pin must start LOW
// Initialize the sensor's trigger pin to low. If we don't pause
// after setting it to low, sometimes the sensor doesn't work right.
digitalWrite(TRIG, LOW);
delay(500); // .5 seconds
}
int getCM() {
// Send trig pulse
// Triggering the sensor for 10 microseconds will cause it to send out
// 8 ultrasonic (40Khz) bursts and listen for the echos.
digitalWrite(TRIG, HIGH);
delayMicroseconds(10);
digitalWrite(TRIG, LOW);
int now = micros();
// Wait for echo start
// The sensor will raise the echo pin high for the length of time that it took
// the ultrasonic bursts to travel round trip.
while (digitalRead(ECHO) == LOW && micros() - now < 30000);
recordPulseLength();
long travelTimeUsec = endTimeUsec - startTimeUsec;
double distanceMeters = 100 * ((travelTimeUsec / 1000000.0) * 340.29) / 2;
//Wait for echo end
long startTime = micros();
while (digitalRead(ECHO) == HIGH);
long travelTime = micros() - startTime;
//Get distance in cm
int distance = travelTime * 34000 / 2;
return distanceMeters * 100;
}
int runUltrasonicClient() {
int count = 0;
setupUltrasonic();
while (count < 60) {
printf("Distance: %dcm\n", getCM());
count++;
delay(500); // 0.5 second
}
return 0;
}