Question

我正在设置一个PHP页面来控制使用树莓派的一些基本传感器。我正在处理我自己的PHP代码，但多年以来我甚至触及了编码，而且我对C语言感到茫然。我已经编译了下面的代码，它运行良好，我从传感器获取数据。我能够将数据移植到PHP中而不会出现问题。我希望能够做的是将一个参数传递给已编译的C程序，该程序将是哪个PIN读取树莓派。

define DHT_PIN 29（数字29是我希望通过命令行参数传递的。）

C代码：

#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#define MAX_TIMINGS 85
#define DHT_PIN 29
int data[5] = { 0, 0, 0, 0, 0 };

void read_dht_data()
{
    uint8_t laststate    = HIGH;
    uint8_t counter        = 0;
    uint8_t j            = 0, i;

    data[0] = data[1] = data[2] = data[3] = data[4] = 0;

    /* pull pin down for 18 milliseconds */
    pinMode( DHT_PIN, OUTPUT );
    digitalWrite( DHT_PIN, LOW );
    delay( 18 );

    /* prepare to read the pin */
    pinMode( DHT_PIN, INPUT );

    /* detect change and read data */
    for ( i = 0; i < MAX_TIMINGS; i++ )
    {
        counter = 0;
        while ( digitalRead( DHT_PIN ) == laststate )
        {
            counter++;
            delayMicroseconds( 1 );
            if ( counter == 255 )
            {
                break;
            }
        }
        laststate = digitalRead( DHT_PIN );

        if ( counter == 255 )
            break;

        /* ignore first 3 transitions */
        if ( (i >= 4) && (i % 2 == 0) )
        {
            /* shove each bit into the storage bytes */
            data[j / 8] <<= 1;
            if ( counter > 16 )
                data[j / 8] |= 1;
            j++;
        }
    }

    /*
     * check we read 40 bits (8bit x 5 ) + verify checksum in the last byte
     * print it out if data is good
     */

    if ( (j >= 40) &&
         (data[4] == ( (data[0] + data[1] + data[2] + data[3]) & 0xFF) ) )
    {
        float h = (float)((data[0] << 8) + data[1]) / 10;
        if ( h > 100 )
        {
            h = data[0];    // for DHT11
        }
        float c = (float)(((data[2] & 0x7F) << 8) + data[3]) / 10;
        if ( c > 125 )
        {
            c = data[2];    // for DHT11
        }
        if ( data[2] & 0x80 )
        {
            c = -c;
        }
        printf( "%.1f %% %.1f *C\n", h, c );
    }
    else  {
       printf( "Data not good, skip\n" );
    }
}

int main( void )
{
    printf( "DHT22 temperature/humidity test\n" );

    if ( wiringPiSetup() == -1 )
        exit( 1 );

    read_dht_data();
}

我尝试过阅读，但C不是我的语言。我正在寻求一些帮助来完成我的任务。

Answer 1

您需要更改main函数的原型，然后解析所提供的参数：

#include <wiringPi.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

#define MAX_TIMINGS 85
int data[5] = { 0, 0, 0, 0, 0 };

void read_dht_data(long dhtPin)
{
    uint8_t laststate    = HIGH;
    uint8_t counter        = 0;
    uint8_t j            = 0, i;

    data[0] = data[1] = data[2] = data[3] = data[4] = 0;

    /* pull pin down for 18 milliseconds */
    pinMode( dhtPin, OUTPUT );
    digitalWrite( dhtPin, LOW );
    delay( 18 );

    /* prepare to read the pin */
    pinMode( dhtPin, INPUT );

    /* detect change and read data */
    for ( i = 0; i < MAX_TIMINGS; i++ )
    {
        counter = 0;
        while ( digitalRead( dhtPin ) == laststate )
        {
            counter++;
            delayMicroseconds( 1 );
            if ( counter == 255 )
            {
                break;
            }
        }
        laststate = digitalRead( dhtPin );

        if ( counter == 255 )
            break;

        /* ignore first 3 transitions */
        if ( (i >= 4) && (i % 2 == 0) )
        {
            /* shove each bit into the storage bytes */
            data[j / 8] <<= 1;
            if ( counter > 16 )
                data[j / 8] |= 1;
            j++;
        }
    }
}

int main(int argc, char * argv[])
{
  if (argc != 2)
  {
    printf("You must specify the DHT pin\n");
    return 1;
  }

  char *end;
  long dhtPin = strtol(argv[1], &end, 10);
  if (end == argv[1])
  {
    printf("Invalid number\n");
    return 1;
  }

  if ( wiringPiSetup() == -1 )
    return 1;

  read_dht_data(dhtPin);
  return 0;
}

如果需要更复杂的参数解析，请参阅getopt函数。

Answer 2

像这样使用argv []（假设参数是一个整数）：

int dht_pin = atoi(argv[1])

您需要将main定义为：

int main(int argc, char *argv[])
{ ... }

atoi（）是stdlib.h的一部分

C现有C代码中的命令行参数

2 个答案: