/*  Python module for DHT temperature/humidity sensors
 *
 *  Modified by Qingping Hou from DHT reader example, original header:
 *
 *  How to access GPIO registers from C-code on the Raspberry-Pi
 *  Example program
 *  15-January-2012
 *  Dom and Gert
 */
#define _BSD_SOURCE // for usleep

#define MAXTIMINGS 100

//#define DEBUG

#define DHT11 11
#define DHT22 22
#define AM2302 22

#include "dhtreader.h"

int readDHT(int type, int pin, float *temp_p, float *hum_p)
{
	int counter = 0;
	int laststate = HIGH;
	int i = 0;
	int j = 0;
	int checksum = 0;
#ifdef DEBUG
	int bitidx = 0;
	int bits[250];
#endif
	int data[100];

	// Set GPIO pin to output
	bcm2835_gpio_fsel(pin, BCM2835_GPIO_FSEL_OUTP);

	bcm2835_gpio_write(pin, HIGH);
	usleep(500000);  // 500 ms
	bcm2835_gpio_write(pin, LOW);
	usleep(20000);

	bcm2835_gpio_fsel(pin, BCM2835_GPIO_FSEL_INPT);

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

	// wait for pin to drop?
	while (bcm2835_gpio_lev(pin) == 1) {
		usleep(1);
	}

	// read data!
	for (i = 0; i < MAXTIMINGS; i++) {
		counter = 0;
		while ( bcm2835_gpio_lev(pin) == laststate) {
			counter++;
			//nanosleep(1);		// overclocking might change this?
			if (counter == 1000)
				break;
		}
		laststate = bcm2835_gpio_lev(pin);
		if (counter == 1000) break;
#ifdef DEBUG
		bits[bitidx++] = counter;
#endif

		if ((i>3) && (i%2 == 0)) {
			// shove each bit into the storage bytes
			data[j/8] <<= 1;
			if (counter > 200)
				data[j/8] |= 1;
			j++;
		}
	}

#ifdef DEBUG
	for (int ii=3; ii<bitidx; ii+=2) {
		printf("bit %d: %d\n", ii-3, bits[ii]);
		printf("bit %d: %d (%d)\n", ii-2, bits[ii+1], bits[ii+1] > 200);
	}
	printf("Data (%d): 0x%x 0x%x 0x%x 0x%x 0x%x\n", j, data[0], data[1], data[2], data[3], data[4]);
#endif

	if (j >= 39) {
		checksum = (data[0] + data[1] + data[2] + data[3]) & 0xFF;
		if (data[4] == checksum) {
			/* yay! checksum is valid */
			if (type == DHT11) {
				/*printf("Temp = %d *C, Hum = %d \%\n", data[2], data[0]);*/
				*temp_p = (float)data[2];
				*hum_p = (float)data[0];
			} else if (type == DHT22) {
				*hum_p = data[0] * 256 + data[1];
				*hum_p /= 10;

				*temp_p = (data[2] & 0x7F)* 256 + data[3];
				*temp_p /= 10.0;
				if (data[2] & 0x80)
					*temp_p *= -1;
				/*printf("Temp =  %.1f *C, Hum = %.1f \%\n", f, h);*/
			}
			return 0;
		}
		return -2;
	}

	return -1;
}