--- /dev/null
+/****************************************************************************
+ * extdrv/dht11.c
+ *
+ *
+ *
+ * Copyright 2013 Nathael Pajani <nathael.pajani@ed3l.fr>
+ *
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ *************************************************************************** */
+
+/*
+ * Support for the DHT11 Temperature and Humidity sensor
+ * Remember that the sensor operates on 3.5 to 5.5V, and that a level shifter must
+ * be used to interface with the DHT11 sensor.
+ *
+ * Note : This support uses a lot of "sleep()" calls, and is thus very ineficient
+ * and many data conversion can occur (checksum errors, though on all of my tests
+ * the errors were always on the lower bit, when the temp and humidity values
+ * were changing, and the scope always reported very stable signals, so I suspect
+ * that the error is not on the micro-controler side ... )
+ * The addition of the "epsilon_error" with a value of 1 removed all errors on my
+ * side., while still getting coherent values.
+ *
+ * DHT11 protocol can be found here : http://embedded-lab.com/blog/?p=4333
+ *
+ */
+
+#include <stdint.h>
+#include "core/lpc_regs_12xx.h"
+#include "core/system.h"
+#include "core/pio.h"
+#include "lib/stdio.h"
+#include "drivers/gpio.h"
+#include "drivers/serial.h"
+#include "extdrv/status_led.h"
+
+
+static struct pio dht11_gpio;
+void dht11_config(const struct pio* gpio)
+{
+ /* Configure as output and set it high. */
+ /* This is the "do nothing" state */
+ config_gpio(gpio, LPC_IO_MODE_PULL_UP, GPIO_DIR_OUT, 1);
+ pio_copy(&dht11_gpio, gpio);
+}
+
+static unsigned char dht11_read_dat()
+{
+ struct lpc_gpio* gpio_port_regs = LPC_GPIO_REGS(dht11_gpio.port);
+ int i = 0;
+ unsigned char val = 0;
+ for (i = 0; i < 8; i++) {
+ /* Wait end of 'low' */
+ while(!(gpio_port_regs->in & (1 << dht11_gpio.pin)));
+
+ /* Wait 35us */
+ usleep(35);
+
+ /* read one bit */
+ if (gpio_port_regs->in & (1 << dht11_gpio.pin)) {
+ val |= (1 << (7-i));
+ }
+
+ /* Wait end of bit */
+ while (gpio_port_regs->in & (1 << dht11_gpio.pin));
+ }
+ return val;
+}
+
+void dht11_display(int serial_num, int epsilon_error)
+{
+ struct lpc_gpio* gpio_port_regs = LPC_GPIO_REGS(dht11_gpio.port);
+ unsigned char data[5];
+ unsigned char checksum = 0;
+ char buff[60];
+ int len = 0, err = 0, i = 0;
+
+ /* Set pin as output */
+ gpio_port_regs->data_dir |= (1 << dht11_gpio.pin);
+
+ /* Send the "start" bit : low pulse of more than 18ms */
+ gpio_port_regs->clear = (1 << dht11_gpio.pin);
+ msleep(25);
+ gpio_port_regs->set = (1 << dht11_gpio.pin);
+
+ /* Set pin as input */
+ gpio_port_regs->data_dir &= ~(1 << dht11_gpio.pin);
+
+ /* Wait for start condition ack : 80us low followed by 80us high.
+ * Do not care about the durations */
+ while (gpio_port_regs->in & (1 << dht11_gpio.pin));
+ while (!(gpio_port_regs->in & (1 << dht11_gpio.pin)));
+ while (gpio_port_regs->in & (1 << dht11_gpio.pin));
+
+ /* Start reading data : 40 bits */
+ for (i = 0; i < 5; i++){
+ data[i] = dht11_read_dat();
+ if (i < 4) {
+ checksum += data[i];
+ }
+ }
+
+ if (checksum != data[4]) {
+ if (epsilon_error == 0) {
+ err = 1;
+ } else if ((checksum < (data[4] - epsilon_error)) && (checksum > (data[4] + epsilon_error))) {
+ err = 1;
+ }
+ }
+ if (err == 1) {
+ status_led(red_only);
+ len = snprintf(buff, 60, "TH_ERR - H: 0x%02x,0x%02x - T: 0x%02x,0x%02x - C: 0x%02x\r\n",
+ data[0], data[1], data[2], data[3], data[4]);
+ serial_write(serial_num, buff, len);
+ return;
+ }
+
+ len = snprintf(buff, 25, "H: %d,%d - T: %d,%d\r\n", data[0], data[1], data[2], data[3]);
+ serial_write(serial_num, buff, len);
+ status_led(green_only);
+}
--- /dev/null
+/****************************************************************************
+ * extdrv/dht11.h
+ *
+ *
+ *
+ * Copyright 2013 Nathael Pajani <nathael.pajani@ed3l.fr>
+ *
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program. If not, see <http://www.gnu.org/licenses/>.
+ *
+ *************************************************************************** */
+
+#ifndef EXTDRV_DHT11_H
+#define EXTDRV_DHT11_H
+
+/*
+ * Support for the DHT11 Temperature and Humidity sensor
+ * Remember that the sensor operates on 3.5 to 5.5V, and that a level shifter must
+ * be used to interface with the DHT11 sensor.
+ *
+ * Note : This support uses a lot of "sleep()" calls, and is thus very ineficient
+ * and many data conversion can occur (checksum errors, though on all of my tests
+ * the errors were always on the lower bit, when the temp and humidity values
+ * were changing, and the scope always reported very stable signals, so I suspect
+ * that the error is not on the micro-controler side ... )
+ * The addition of the "epsilon_error" with a value of 1 removed all errors on my
+ * side., while still getting coherent values.
+ *
+ * DHT11 protocol can be found here : http://embedded-lab.com/blog/?p=4333
+ *
+ */
+
+#include <stdint.h>
+
+/***************************************************************************** */
+/* DHT11 Humidity and temp sensor configuration : Set up the GPIO used for
+ * communication with the DHT11 sensor
+ */
+void dht11_config(const struct pio* gpio);
+
+/* Display both temperature and humidity values on the given serial line.
+ * serial_num is the serial line number (0 or 1)
+ * epsilon_error is the allowed error on the checksum
+ */
+void dht11_display(int serial_num, int epsilon_error);
+
+
+
+#endif /* EXTDRV_DHT11_H */
+
