humid_sht.c

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/*
 * Copyright (C) 2008-2014 The Paparazzi team
 *
 * This file is part of paparazzi.
 *
 * paparazzi 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, or (at your option)
 * any later version.
 *
 * paparazzi 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 paparazzi; see the file COPYING.  If not, write to
 * the Free Software Foundation, 59 Temple Place - Suite 330,
 * Boston, MA 02111-1307, USA.
 */

#include "std.h"
#include "mcu_periph/gpio.h"
#include "mcu_periph/uart.h"
#include "messages.h"
#include "subsystems/datalink/downlink.h"
#include "humid_sht.h"

//#include "led.h"

#define noACK           0
#define ACK             1
#define TEMP            0
#define HUMI            1

//adr    command  r/w
//000    0011     0
#define STATUS_REG_W    0x06
//000    0011     1
#define STATUS_REG_R    0x07
//000    0001     1
#define MEASURE_TEMP    0x03
//000    0010     1
#define MEASURE_HUMI    0x05
//000    1111     0
#define RESET           0x1e


#define SHT_IDLE            0
#define SHT_MEASURING_HUMID 1
#define SHT_MEASURING_TEMP  2

#if !defined SHT_DAT_GPIO || !defined SHT_SCK_GPIO
#error You need to define SHT_DAT_GPIO and SHT_SCK_GPIO
#endif

#define DATA_SET        gpio_setup_input(SHT_DAT_GPIO)
#define DATA_CLR        gpio_setup_output(SHT_DAT_GPIO)
#define DATA_IN         gpio_get(SHT_DAT_GPIO)

#define SCK_SET         gpio_set(SHT_SCK_GPIO)
#define SCK_CLR         gpio_clear(SHT_SCK_GPIO)


uint16_t humidsht, tempsht;
float fhumidsht, ftempsht;
bool_t humid_sht_available;
uint8_t humid_sht_status;

uint8_t s_write_byte(uint8_t value);
uint8_t s_read_byte(uint8_t ack);
void s_transstart(void);
void s_connectionreset(void);
uint8_t s_read_statusreg(uint8_t *p_value, uint8_t *p_checksum);
uint8_t s_write_statusreg(uint8_t *p_value);
uint8_t s_measure(uint16_t *p_value, uint8_t *p_checksum, uint8_t mode);
uint8_t s_start_measure(uint8_t mode);
uint8_t s_read_measure(uint16_t *p_value, uint8_t *p_checksum);
void calc_sht(uint16_t hum, uint16_t tem, float *fhum , float *ftem);
uint8_t humid_sht_reset(void);


uint8_t s_write_byte(uint8_t value)
{
  uint8_t i, error = 0;

  for (i = 0x80; i > 0; i /= 2) {       //shift bit for masking
    if (i & value) { DATA_SET; }            //masking value with i , write to SENSI-BUS
    else { DATA_CLR; }
    SCK_SET;                           //clk for SENSI-BUS
    SCK_SET; SCK_SET; SCK_SET;         //pulswith approx. 5 us
    //     _nop_();_nop_();_nop_();           //pulswith approx. 5 us
    SCK_CLR;
  }
  DATA_SET;                             //release DATA-line
  SCK_SET;                              //clk #9 for ack
  error = DATA_IN;                      //check ack (DATA will be pulled down by SHT11)
  SCK_CLR;

  return error;                         //error=1 in case of no acknowledge
}

uint8_t s_read_byte(uint8_t ack)
{
  uint8_t i, val = 0;

  DATA_SET;                             //release DATA-line
  for (i = 0x80; i > 0; i /= 2) {       //shift bit for masking
    SCK_SET;                            //clk for SENSI-BUS
    if (DATA_IN) { val = (val | i); }       //read bit
    SCK_CLR;
  }

  if (ack) { DATA_CLR; }                    //in case of "ack==1" pull down DATA-Line
  SCK_SET;                              //clk #9 for ack
  SCK_SET; SCK_SET; SCK_SET;            //pulswith approx. 5 us
  //  _nop_();_nop_();_nop_();              //pulswith approx. 5 us
  SCK_CLR;
  DATA_SET;                             //release DATA-line
  return val;
}

void s_transstart(void)
{
  // generates a transmission start
  //       _____         ________
  // DATA:      |_______|
  //           ___     ___
  // SCK : ___|   |___|   |______

  DATA_SET; SCK_CLR;                      //Initial state
  SCK_CLR;//  _nop_();
  SCK_SET;
  SCK_SET;//  _nop_();
  DATA_CLR;
  DATA_CLR;//  _nop_();
  SCK_CLR;
  SCK_CLR; SCK_CLR; SCK_CLR; //  _nop_();_nop_();_nop_();
  SCK_SET;
  SCK_SET;//  _nop_();
  DATA_SET;
  DATA_SET;//  _nop_();
  SCK_CLR;
}

void s_connectionreset(void)
{
  // communication reset: DATA-line=1 and at least 9 SCK cycles followed by transstart
  //          _____________________________________________________         ________
  // DATA:                                                         |_______|
  //             _    _    _    _    _    _    _    _    _        ___     ___
  // SCK :    __| |__| |__| |__| |__| |__| |__| |__| |__| |______|   |___|   |______

  uint8_t i;

  DATA_SET; SCK_CLR;                    //Initial state
  for (i = 0; i < 9; i++) {             //9 SCK cycles
    SCK_SET;
    SCK_CLR;
  }
  s_transstart();                       //transmission start
}

uint8_t s_read_statusreg(uint8_t *p_value, uint8_t *p_checksum)
{
  // reads the status register with checksum (8-bit)
  uint8_t error = 0;

  s_transstart();                   //transmission start
  error = s_write_byte(STATUS_REG_R); //send command to sensor
  *p_value = s_read_byte(ACK);      //read status register (8-bit)
  *p_checksum = s_read_byte(noACK); //read checksum (8-bit)
  return error;                     //error=1 in case of no response form the sensor
}

uint8_t s_write_statusreg(uint8_t *p_value)
{
  // writes the status register with checksum (8-bit)
  uint8_t error = 0;

  s_transstart();                   //transmission start
  error += s_write_byte(STATUS_REG_W); //send command to sensor
  error += s_write_byte(*p_value);  //send value of status register
  return error;                     //error>=1 in case of no response form the sensor
}

uint8_t s_measure(uint16_t *p_value, uint8_t *p_checksum, uint8_t mode)
{
  // makes a measurement (humidity/temperature) with checksum
  uint8_t error = 0;
  uint32_t i;

  s_transstart();                   //transmission start
  switch (mode) {                   //send command to sensor
    case TEMP : error += s_write_byte(MEASURE_TEMP); break;
    case HUMI : error += s_write_byte(MEASURE_HUMI); break;
    default      : break;
  }
  for (i = 0; i < 6665535; i++) if (DATA_IN == 0) { break; } //wait until sensor has finished the measurement
  if (DATA_IN) { error += 1; }                    // or timeout (~2 sec.) is reached
  *(p_value) = s_read_byte(ACK) << 8;         //read the first byte (MSB)
  *(p_value) |= s_read_byte(ACK);             //read the second byte (LSB)
  *p_checksum = s_read_byte(noACK);           //read checksum

  return error;
}

uint8_t s_start_measure(uint8_t mode)
{
  // makes a measurement (humidity/temperature) with checksum
  uint8_t error = 0;

  s_transstart();                   //transmission start
  switch (mode) {                   //send command to sensor
    case TEMP : error += s_write_byte(MEASURE_TEMP); break;
    case HUMI : error += s_write_byte(MEASURE_HUMI); break;
    default      : break;
  }

  return error;
}

uint8_t s_read_measure(uint16_t *p_value, uint8_t *p_checksum)
{
  // reads a measurement (humidity/temperature) with checksum
  uint8_t error = 0;

  if (DATA_IN) { error += 1; }                    //still busy?
  *(p_value) = s_read_byte(ACK) << 8;         //read the first byte (MSB)
  *(p_value) |= s_read_byte(ACK);             //read the second byte (LSB)
  *p_checksum = s_read_byte(noACK);           //read checksum

  return error;
}

void calc_sht(uint16_t hum, uint16_t tem, float *fhum , float *ftem)
{
  // calculates temperature [ C] and humidity [%RH]
  // input : humi [Ticks] (12 bit)
  //             temp [Ticks] (14 bit)
  // output: humi [%RH]
  //             temp [ C]

  const float C1 = -4.0;            // for 12 Bit
  const float C2 = 0.0405;          // for 12 Bit
  const float C3 = -0.0000028;      // for 12 Bit
  const float T1 = 0.01;            // for 14 Bit @ 5V
  const float T2 = 0.00008;         // for 14 Bit @ 5V
  float rh;                         // rh:      Humidity [Ticks] 12 Bit
  float t;                          // t:       Temperature [Ticks] 14 Bit
  float rh_lin;                     // rh_lin:  Humidity linear
  float rh_true;                    // rh_true: Temperature compensated humidity
  float t_C;                        // t_C   :  Temperature [ C]

  rh = (float)hum;                  //converts integer to float
  t = (float)tem;                   //converts integer to float

  t_C = t * 0.01 - 39.66;           //calc. Temperature from ticks to [°C] @ 3.5V
  rh_lin = C3 * rh * rh + C2 * rh + C1; //calc. Humidity from ticks to [%RH]
  rh_true = (t_C - 25) * (T1 + T2 * rh) + rh_lin; //calc. Temperature compensated humidity [%RH]
  if (rh_true > 100) { rh_true = 100; } //cut if the value is outside of
  if (rh_true < 0.1) { rh_true = 0.1; } //the physical possible range
  *ftem = t_C;                      //return temperature [ C]
  *fhum = rh_true;                  //return humidity[%RH]
}

uint8_t humid_sht_reset(void)
{
  // resets the sensor by a softreset
  uint8_t error = 0;

  s_connectionreset();                  //reset communication
  error += s_write_byte(RESET);         //send RESET-command to sensor

  return error;                         //error=1 in case of no response form the sensor
}

void humid_sht_init(void)
{
  /* Configure DAT/SCL pin as GPIO */
  gpio_setup_input(SHT_DAT_GPIO);
  gpio_setup_output(SHT_SCK_GPIO);
  gpio_clear(SHT_SCK_GPIO);


  humid_sht_available = FALSE;
  humid_sht_status = SHT_IDLE;
}

void humid_sht_periodic(void)
{
  uint8_t error = 0, checksum;

  if (humid_sht_status == SHT_IDLE) {
    /* init humidity read */
    s_connectionreset();
    s_start_measure(HUMI);
    humid_sht_status = SHT_MEASURING_HUMID;
  } else if (humid_sht_status == SHT_MEASURING_HUMID) {
    /* get data */
    error += s_read_measure(&humidsht, &checksum);

    if (error != 0) {
      s_connectionreset();
      s_start_measure(HUMI);    //restart
      //LED_TOGGLE(2);
    } else {
      error += s_start_measure(TEMP);
      humid_sht_status = SHT_MEASURING_TEMP;
    }
  } else if (humid_sht_status == SHT_MEASURING_TEMP) {
    /* get data */
    error += s_read_measure(&tempsht, &checksum);

    if (error != 0) {
      s_connectionreset();
      s_start_measure(TEMP);    //restart
      //LED_TOGGLE(2);
    } else {
      calc_sht(humidsht, tempsht, &fhumidsht, &ftempsht);
      humid_sht_available = TRUE;
      s_connectionreset();
      s_start_measure(HUMI);
      humid_sht_status = SHT_MEASURING_HUMID;
      DOWNLINK_SEND_SHT_STATUS(DefaultChannel, DefaultDevice, &humidsht, &tempsht, &fhumidsht, &ftempsht);
      humid_sht_available = FALSE;
    }
  }
}