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RIOT/drivers/sht1x/sht1x.c

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/*
* Copyright 2009 Freie Universitaet Berlin (FUB)
* 2018 Otto-von-Guericke-Universität Magdeburg
*
* This file is subject to the terms and conditions of the GNU Lesser
* General Public License v2.1. See the file LICENSE in the top level
* directory for more details.
*/
/**
* @ingroup drivers_sht1x
* @brief Driver for the Sensirion SHT10/SHT11/SHT15 humidity and
* temperature sensor
* @{
*
* @file
* @brief SHT10/SHT11/SHT15 Device Driver
* @author Marian Buschsieweke <marian.buschsieweke@ovgu.de>
*
* @}
*/
#include <errno.h>
#include <stdint.h>
#include "xtimer.h"
#include "sht1x.h"
#include "sht1x_defines.h"
#include "bitarithm.h"
#include "container.h"
#define ENABLE_DEBUG 0
#include "debug.h"
/**
* @brief Perform measurement
*
* @param dev SHT1X device to use
* @param value Measured value
* @param mode The requested measurement mode: temperature or humidity
*
* @retval 0 Success
* @retval -EIO I/O failure (`gpio_init()` failed)
* @retval -EBADMSG CRC-8 checksum didn't match
* @retval -EPROTO SHT1x did not acknowledge command
* @retval -ECANCELED Measurement timed out
*/
static int measure(const sht1x_dev_t *dev, uint16_t *value, uint8_t mode);
/**
* @brief Write one byte
*
* @param dev SHT1X device to send the byte to
* @param value The value to write
*
* @retval 1 Write was acknowledged
* @retval 0 Write was *NOT* acknowledged (communication failure)
* @retval -EIO I/O failure (`gpio_init()` failed)
*/
static int write_byte(const sht1x_dev_t *dev, uint8_t value);
/**
* @brief Read one byte
*
* @param dev SHT1X device to receive the byte from
* @param dest Store the received byte here
* @param ack `SHT1X_ACK` to acknowledge byte, `SHT1X_NO_ACK` otherwise
*
* @retval 0 Success
* @retval -EIO I/O failure (`gpio_init()` failed)
*/
static int read_byte(const sht1x_dev_t *dev, uint8_t *dest, int ack);
/**
* @brief Communication reset
*
* @param dev SHT1X device to reset the connection to
*
* @retval 0 Success
* @retval -EIO I/O failure (`gpio_init()` failed)
*/
static int connection_reset(const sht1x_dev_t *dev);
/**
* @brief Send start of transmission sequence
*
* @param dev SHT1X device to send the transmission start sequence to
*
* @retval 0 Success
* @retval -EIO I/O failure (`gpio_init()` failed)
*/
static int transmission_start(const sht1x_dev_t *dev);
/**
* @brief Toggle the clock line
*
* @param dev SHT1X device to send one clock signal to
*/
static inline void clk_signal(const sht1x_dev_t *dev);
/**
* @brief Calculate the initial value of the CRC-8 checksum
*
* @param status The current sensor status
*
* @return The initial value of the CRC-8 checksum
*/
static inline uint8_t crc_initial_value(uint8_t status);
/**
* @brief Reverse the order of bits in a byte (needed for CRC)
*
* @param value The byte to reverse the bits of
*
* @return The reversed input
*/
static inline uint8_t reverse_byte(uint8_t value);
/**
* @brief Look up table required for CRC-8 calculation
*
* Values taken from the Application Note PDF of Sensirion (December 2011)
*/
static const uint8_t crc_lookup_table[] = {
0x00, 0x31, 0x62, 0x53, 0xc4, 0xf5, 0xa6, 0x97,
0xb9, 0x88, 0xdb, 0xea, 0x7d, 0x4c, 0x1f, 0x2e,
0x43, 0x72, 0x21, 0x10, 0x87, 0xb6, 0xe5, 0xd4,
0xfa, 0xcb, 0x98, 0xa9, 0x3e, 0x0f, 0x5c, 0x6d,
0x86, 0xb7, 0xe4, 0xd5, 0x42, 0x73, 0x20, 0x11,
0x3f, 0x0e, 0x5d, 0x6c, 0xfb, 0xca, 0x99, 0xa8,
0xc5, 0xf4, 0xa7, 0x96, 0x01, 0x30, 0x63, 0x52,
0x7c, 0x4d, 0x1e, 0x2f, 0xb8, 0x89, 0xda, 0xeb,
0x3d, 0x0c, 0x5f, 0x6e, 0xf9, 0xc8, 0x9b, 0xaa,
0x84, 0xb5, 0xe6, 0xd7, 0x40, 0x71, 0x22, 0x13,
0x7e, 0x4f, 0x1c, 0x2d, 0xba, 0x8b, 0xd8, 0xe9,
0xc7, 0xf6, 0xa5, 0x94, 0x03, 0x32, 0x61, 0x50,
0xbb, 0x8a, 0xd9, 0xe8, 0x7f, 0x4e, 0x1d, 0x2c,
0x02, 0x33, 0x60, 0x51, 0xc6, 0xf7, 0xa4, 0x95,
0xf8, 0xc9, 0x9a, 0xab, 0x3c, 0x0d, 0x5e, 0x6f,
0x41, 0x70, 0x23, 0x12, 0x85, 0xb4, 0xe7, 0xd6,
0x7a, 0x4b, 0x18, 0x29, 0xbe, 0x8f, 0xdc, 0xed,
0xc3, 0xf2, 0xa1, 0x90, 0x07, 0x36, 0x65, 0x54,
0x39, 0x08, 0x5b, 0x6a, 0xfd, 0xcc, 0x9f, 0xae,
0x80, 0xb1, 0xe2, 0xd3, 0x44, 0x75, 0x26, 0x17,
0xfc, 0xcd, 0x9e, 0xaf, 0x38, 0x09, 0x5a, 0x6b,
0x45, 0x74, 0x27, 0x16, 0x81, 0xb0, 0xe3, 0xd2,
0xbf, 0x8e, 0xdd, 0xec, 0x7b, 0x4a, 0x19, 0x28,
0x06, 0x37, 0x64, 0x55, 0xc2, 0xf3, 0xa0, 0x91,
0x47, 0x76, 0x25, 0x14, 0x83, 0xb2, 0xe1, 0xd0,
0xfe, 0xcf, 0x9c, 0xad, 0x3a, 0x0b, 0x58, 0x69,
0x04, 0x35, 0x66, 0x57, 0xc0, 0xf1, 0xa2, 0x93,
0xbd, 0x8c, 0xdf, 0xee, 0x79, 0x48, 0x1b, 0x2a,
0xc1, 0xf0, 0xa3, 0x92, 0x05, 0x34, 0x67, 0x56,
0x78, 0x49, 0x1a, 0x2b, 0xbc, 0x8d, 0xde, 0xef,
0x82, 0xb3, 0xe0, 0xd1, 0x46, 0x77, 0x24, 0x15,
0x3b, 0x0a, 0x59, 0x68, 0xff, 0xce, 0x9d, 0xac,
};
/** @brief Lookuptable for d1 parameter depending on supply voltage */
static const int16_t sht1x_d1[] = { -4010, -3980, -3970, -3960, -3940 };
static inline void clk_signal(const sht1x_dev_t *dev)
{
gpio_set(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
}
static int write_byte(const sht1x_dev_t *dev, uint8_t value)
{
int ack;
if (gpio_init(dev->data, GPIO_OUT) == -1) {
return -EIO;
}
/* send value bit by bit to sht1x */
for (int i = 0; i < 8; i++) {
if (value & BIT7) {
gpio_set(dev->data);
}
else {
gpio_clear(dev->data);
}
xtimer_usleep(SHT1X_HALF_CLOCK);
/* trigger clock signal */
clk_signal(dev);
/* shift value to write next bit */
value <<= 1;
}
/* wait for ack */
if (gpio_init(dev->data, GPIO_IN) == -1) {
return -EIO;
}
xtimer_usleep(SHT1X_HALF_CLOCK);
ack = gpio_read(dev->data);
clk_signal(dev);
return ack;
}
static int read_byte(const sht1x_dev_t *dev, uint8_t *dest, int ack)
{
uint8_t value = 0;
xtimer_usleep(SHT1X_HALF_CLOCK);
/* read value bit by bit */
for (int i = 0; i < 8; i++) {
value <<= 1;
gpio_set(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
if (gpio_read(dev->data)) {
/* set bit when DATA is high */
value |= 0x01;
}
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
}
/* send ack if necessary */
if (gpio_init(dev->data, GPIO_OUT) == -1) {
return -EIO;
}
gpio_write(dev->data, ack);
xtimer_usleep(SHT1X_HALF_CLOCK);
clk_signal(dev);
/* release data line */
if (gpio_init(dev->data, GPIO_IN) == -1) {
return -EIO;
}
*dest = value;
return 0;
}
static int transmission_start(const sht1x_dev_t *dev)
{
/* _____ ________
DATA: |_______|
___ ___
SCK : ___| |___| |______
*/
if (gpio_init(dev->data, GPIO_OUT) == -1) {
return -EIO;
}
/* set initial state */
gpio_set(dev->data);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_set(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->data);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_set(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_set(dev->data);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
if (gpio_init(dev->data, GPIO_IN) == -1) {
return -EIO;
}
return 0;
}
static int connection_reset(const sht1x_dev_t *dev)
{
/* _____________________________________________________ ____
DATA: |_______|
_ _ _ _ _ _ _ _ _ ___ ___
SCK : __| |__| |__| |__| |__| |__| |__| |__| |__| |______| |___| |__
*/
if (gpio_init(dev->data, GPIO_OUT) == -1) {
return -EIO;
}
gpio_set(dev->data);
xtimer_usleep(SHT1X_HALF_CLOCK);
gpio_clear(dev->clk);
xtimer_usleep(SHT1X_HALF_CLOCK);
for (int i = 0; i < 9; i++) {
clk_signal(dev);
}
return transmission_start(dev);
}
static inline uint8_t crc_initial_value(uint8_t status)
{
status &= 0x07;
return (((0x01 & status) << 7) | ((0x02 & status) << 5) | ((0x04 & status) << 3));
}
static inline uint8_t reverse_byte(uint8_t value)
{
uint8_t result = (value & 0x01) << 7;
result |= (value & 0x02) << 5;
result |= (value & 0x04) << 3;
result |= (value & 0x08) << 1;
result |= (value & 0x10) >> 1;
result |= (value & 0x20) >> 3;
result |= (value & 0x40) >> 5;
result |= (value & 0x80) >> 7;
return result;
}
static int measure(const sht1x_dev_t *dev, uint16_t *value, uint8_t mode)
{
uint8_t data[2] = { 0, 0 };
int retval;
retval = transmission_start(dev);
if (retval != 0) {
return retval;
}
switch (write_byte(dev, mode)) {
case -EIO:
return -EIO;
case 0:
break;
default:
case 1:
return -EPROTO;
}
/* wait until sensor has finished measurement or timeout */
{
int ack = 1;
for (int i = 0; ack != 0; i++) {
if (i > SHT1X_MEASURE_TIMEOUT) {
return -ECANCELED;
}
xtimer_usleep(1000);
ack = gpio_read(dev->data);
}
}
/* read MSB */
retval = read_byte(dev, &data[0], SHT1X_ACK);
if (retval != 0) {
return retval;
}
/* read LSB, send ACK only if CRC checking is enabled */
retval = (dev->conf & SHT1X_CONF_SKIP_CRC) ? SHT1X_NO_ACK : SHT1X_ACK;
retval = read_byte(dev, &data[1], retval);
if (retval != 0) {
return retval;
}
if (!(dev->conf & SHT1X_CONF_SKIP_CRC)) {
uint8_t crc;
uint8_t expected;
retval = read_byte(dev, &crc, SHT1X_NO_ACK);
if (retval != 0) {
return retval;
}
expected = crc_initial_value(dev->conf);
expected = crc_lookup_table[expected ^ mode];
expected = crc_lookup_table[expected ^ data[0]];
expected = crc_lookup_table[expected ^ data[1]];
expected = reverse_byte(expected);
if (expected != crc) {
DEBUG("[sht1x] CRC expected: 0x%02x, got: 0x%02x\n"
" CRC0: 0x%02x, CMD: 0x%02x, data: {0x%02x, 0x%02x}\n",
(int)expected, (int)crc,
(int)crc_initial_value(dev->conf), mode,
(int)data[0], (int)data[1]);
return -EBADMSG;
}
}
*value = (((uint16_t)data[0]) << 8) | (uint16_t)data[1];
return 0;
}
int sht1x_init(sht1x_dev_t *dev, const sht1x_params_t *params)
{
if (!dev || !params || (((uint8_t)params->vdd) >= ARRAY_SIZE(sht1x_d1))) {
return -EINVAL;
}
dev->clk = params->clk;
dev->data = params->data;
if (gpio_init(dev->clk, GPIO_OUT) || gpio_init(dev->data, GPIO_IN)) {
return -EIO;
}
dev->temp_off = 0;
dev->hum_off = 0;
dev->conf = 0;
dev->vdd = (uint8_t)params->vdd;
return sht1x_reset(dev);
}
int16_t sht1x_temperature(const sht1x_dev_t *dev, uint16_t raw)
{
if (!dev || (dev->vdd >= ARRAY_SIZE(sht1x_d1))) {
return INT16_MIN;
}
int16_t d1 = sht1x_d1[dev->vdd];
int16_t d2 = (dev->conf & SHT1X_CONF_LOW_RESOLUTION) ? 4 : 1;
return d1 + d2 * ((int16_t)raw);
}
int16_t sht1x_humidity(const sht1x_dev_t *dev, uint16_t raw, int16_t temp)
{
if (!dev) {
return -1;
}
static const int32_t c1 = -20468;
static const int32_t t1 = 1;
int32_t c2, c3, c4, t2;
if (dev->conf & SHT1X_CONF_LOW_RESOLUTION) {
c2 = 5872;
c3 = 494801;
c4 = 1000000;
t2 = 781;
}
else {
c2 = 367;
c3 = 791684;
c4 = 100000;
t2 = 12500;
}
/*
* Calculate linear humidity, but slightly different. Original formula:
*
* hum_lin = c1 + c2 * raw + c3 * (raw * raw)
*
* But we use:
*
* hum_lin = c1 + c2 * raw - (c4 * raw / c3') * (c4 * raw / c3')
*
* where: c3' = 1 / (sqrt(-c3) / c4)
*
* (This better fits for integer calculation)
*/
int32_t res = ((int32_t)raw * c4) / c3;
res = c1 + c2 * (int32_t)raw - (res * res);
/*
* Perform temperature compensation, again slightly different.
* Original formula:
*
* hum_true = (temp - 25) * (t1 + t2 * raw) + hum_lin
*
* But we use:
*
* hum_true = (temp - 25) * t1 + (temp - 25) * raw / t2') + hum_lin
*
* where t2' = 1/t2
*/
int32_t temp_diff = temp - 2500;
res = temp_diff * t1 + (temp_diff * (int32_t)raw * 100) / t2 + res;
return (int16_t)(res / 100);
}
int sht1x_read(const sht1x_dev_t *dev, int16_t *temp, int16_t *rel_hum)
{
uint16_t temp_raw;
int16_t t;
uint16_t hum_raw;
int retval;
if (!dev || (dev->vdd >= ARRAY_SIZE(sht1x_d1)) || (!temp && !rel_hum)) {
return -EINVAL;
}
retval = measure(dev, &temp_raw, SHT1X_MEASURE_TEMP);
if (retval != 0) {
connection_reset(dev);
return retval;
}
t = sht1x_temperature(dev, temp_raw) + dev->temp_off;
if (temp != NULL) {
*temp = t;
}
if (rel_hum != NULL) {
retval = measure(dev, &hum_raw, SHT1X_MEASURE_HUM);
if (retval != 0) {
connection_reset(dev);
return retval;
}
*rel_hum = sht1x_humidity(dev, hum_raw, t) + dev->hum_off;
}
return 0;
}
int sht1x_configure(sht1x_dev_t *dev, sht1x_conf_t conf)
{
if (!dev) {
return -EINVAL;
}
/* Apply config that is not stored on the sensor */
dev->conf &= SHT1X_CONF_MASK;
dev->conf |= conf & (~(SHT1X_CONF_MASK));
/* Send new status byte to sensor, if on-device config was changed */
if ((conf & SHT1X_CONF_MASK) != (dev->conf & SHT1X_CONF_MASK)) {
int retval = transmission_start(dev);
if (retval != 0) {
return retval;
}
switch (write_byte(dev, SHT1X_STATUS_REG_W)) {
case -EIO:
return -EIO;
case 0:
break;
default:
case 1:
return -EPROTO;
}
switch (write_byte(dev, conf & SHT1X_CONF_MASK)) {
case -EIO:
return -EIO;
case 0:
break;
default:
case 1:
return -EPROTO;
}
/* Read back uploaded configuration to verify that sensor applied it */
uint8_t status;
retval = sht1x_read_status(dev, &status);
if (retval != 0) {
return retval;
}
if (dev->conf != conf) {
/* Configuration was not applied by sensor */
return -ECANCELED;
}
}
return 0;
}
int sht1x_read_status(sht1x_dev_t *dev, uint8_t *status)
{
int retval;
if (!dev || !status) {
return -EINVAL;
}
retval = transmission_start(dev);
if (retval != 0) {
return retval;
}
switch (write_byte(dev, SHT1X_STATUS_REG_R)) {
case -EIO:
return -EIO;
case 0:
break;
default:
case 1:
return -EPROTO;
}
retval = read_byte(dev, status, SHT1X_ACK);
if (retval != 0) {
return retval;
}
uint8_t crc;
uint8_t expected;
/* read checksum */
retval = read_byte(dev, &crc, SHT1X_NO_ACK);
if (retval != 0) {
return retval;
}
expected = crc_initial_value(*status);
expected = crc_lookup_table[expected ^ SHT1X_STATUS_REG_R];
expected = crc_lookup_table[expected ^ *status];
expected = reverse_byte(expected);
if (expected != crc) {
DEBUG("[sht1x] CRC expected: 0x%02x, got: 0x%02x\n"
" CRC0: 0x%02x, CMD: 0x%02x, data: {0x%02x}\n",
(int)expected, (int)crc,
(int)crc_initial_value(*status), SHT1X_STATUS_REG_R,
(int)*status);
return -EBADMSG;
}
/* Extract config from status and store it after CRC check passed */
dev->conf &= ~(SHT1X_CONF_MASK);
dev->conf |= *status & SHT1X_CONF_MASK;
return 0;
}
int sht1x_reset(sht1x_dev_t *dev)
{
int retval;
if (!dev) {
return -EINVAL;
}
retval = transmission_start(dev);
if (retval != 0) {
return retval;
}
switch (write_byte(dev, SHT1X_RESET)) {
case -EIO:
return -EIO;
case 0:
break;
default:
case 1:
return -EPROTO;
}
dev->conf = 0;
xtimer_usleep(SHT1X_RESET_WAIT);
return 0;
}
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