1 /*
2 * Copyright (c) 2019 Electronut Labs
3 * Copyright (c) 2023 Trent Piepho <tpiepho@gmail.com>
4 *
5 * SPDX-License-Identifier: Apache-2.0
6 */
7
8 #include <zephyr/device.h>
9 #include <zephyr/drivers/i2c.h>
10 #include <zephyr/drivers/sensor.h>
11 #include <zephyr/kernel.h>
12 #include <zephyr/sys/byteorder.h>
13 #include <zephyr/sys/__assert.h>
14 #include <zephyr/drivers/i2c.h>
15 #include <stdio.h>
16 #include <stdlib.h>
17 #include <zephyr/sys/util.h>
18 #include "si7006.h"
19 #include <zephyr/logging/log.h>
20
21 LOG_MODULE_REGISTER(si7006, CONFIG_SENSOR_LOG_LEVEL);
22
23 struct si7006_data {
24 uint16_t temperature;
25 uint16_t humidity;
26 };
27
28 struct si7006_config {
29 struct i2c_dt_spec i2c;
30 /** Use "read temp" vs "read old temp" command, the latter only with SiLabs sensors. */
31 uint8_t read_temp_cmd;
32 };
33
34 /**
35 * @brief function to get relative humidity
36 *
37 * @return int 0 on success
38 */
si7006_get_humidity(const struct device * dev)39 static int si7006_get_humidity(const struct device *dev)
40 {
41 struct si7006_data *si_data = dev->data;
42 const struct si7006_config *config = dev->config;
43 int retval;
44 uint16_t hum;
45
46 retval = i2c_burst_read_dt(&config->i2c, SI7006_MEAS_REL_HUMIDITY_MASTER_MODE,
47 (uint8_t *)&hum, sizeof(hum));
48
49 if (retval == 0) {
50 si_data->humidity = sys_be16_to_cpu(hum) & ~3;
51 } else {
52 LOG_ERR("read register err: %d", retval);
53 }
54
55 return retval;
56 }
57
58 /**
59 * @brief function to get temperature
60 *
61 * Note that for Si7006 type sensors, si7006_get_humidity must be called before
62 * calling si7006_get_temperature, as the get old temperature command is used.
63 *
64 * @return int 0 on success
65 */
66
si7006_get_temperature(const struct device * dev)67 static int si7006_get_temperature(const struct device *dev)
68 {
69 struct si7006_data *si_data = dev->data;
70 const struct si7006_config *config = dev->config;
71 uint16_t temp;
72 int retval;
73
74 retval = i2c_burst_read_dt(&config->i2c, config->read_temp_cmd,
75 (uint8_t *)&temp, sizeof(temp));
76
77 if (retval == 0) {
78 si_data->temperature = sys_be16_to_cpu(temp) & ~3;
79 } else {
80 LOG_ERR("read register err: %d", retval);
81 }
82
83 return retval;
84 }
85
86 /**
87 * @brief fetch a sample from the sensor
88 *
89 * @return 0
90 */
si7006_sample_fetch(const struct device * dev,enum sensor_channel chan)91 static int si7006_sample_fetch(const struct device *dev,
92 enum sensor_channel chan)
93 {
94 int retval;
95
96 retval = si7006_get_humidity(dev);
97 if (retval == 0) {
98 retval = si7006_get_temperature(dev);
99 }
100
101 return retval;
102 }
103
104 /**
105 * @brief sensor value get
106 *
107 * @return -ENOTSUP for unsupported channels
108 */
si7006_channel_get(const struct device * dev,enum sensor_channel chan,struct sensor_value * val)109 static int si7006_channel_get(const struct device *dev,
110 enum sensor_channel chan,
111 struct sensor_value *val)
112 {
113 struct si7006_data *si_data = dev->data;
114
115 if (chan == SENSOR_CHAN_AMBIENT_TEMP) {
116 /* Raw formula: (temp * 175.72) / 65536 - 46.85
117 * To use integer math, scale the 175.72 factor by 128 and move the offset to
118 * inside the division. This gives us:
119 *
120 * (temp * 175.72 * 128 - 46.86 * 128 * 65536) / (65536 * 128)
121 * The constants can be calculated now:
122 * (temp * 22492 - 393006285) / 2^23
123 *
124 * There is a very small amount of round-off error in the factor of 22492. To
125 * compenstate, a constant of 5246 is used to center the error about 0, thus
126 * reducing the overall MSE.
127 */
128
129 /* Temperature value times two to the 23rd power, i.e. temp_23 = temp << 23 */
130 const int32_t temp_23 = si_data->temperature * 22492 - (393006285 - 5246);
131 /* Integer component of temperature */
132 int32_t temp_int = temp_23 >> 23;
133 /* Fractional component of temperature */
134 int32_t temp_frac = temp_23 & BIT_MASK(23);
135
136 /* Deal with the split twos-complement / BCD format oddness with negatives */
137 if (temp_23 < 0) {
138 temp_int += 1;
139 temp_frac -= BIT(23);
140 }
141 val->val1 = temp_int;
142 /* Remove a constant factor of 64 from (temp_frac * 1000000) >> 23 */
143 val->val2 = (temp_frac * 15625ULL) >> 17;
144
145 LOG_DBG("temperature %u = val1:%d, val2:%d", si_data->temperature,
146 val->val1, val->val2);
147
148 return 0;
149 } else if (chan == SENSOR_CHAN_HUMIDITY) {
150 /* Humidity times two to the 16th power. Offset of -6 not applied yet. */
151 const uint32_t rh_16 = si_data->humidity * 125U;
152 /* Integer component of humidity */
153 const int16_t rh_int = rh_16 >> 16;
154 /* Fraction component of humidity */
155 const uint16_t rh_frac = rh_16 & BIT_MASK(16);
156
157 val->val1 = rh_int - 6; /* Apply offset now */
158 /* Remove a constant factor of 64 from (rh_frac * 1000000) >> 16 */
159 val->val2 = (rh_frac * 15625) >> 10;
160
161 /* Deal with the split twos-complement / BCD format oddness with negatives */
162 if (val->val1 < 0) {
163 val->val1 += 1;
164 val->val2 -= 1000000;
165 }
166
167 LOG_DBG("humidity %u = val1:%d, val2:%d", si_data->humidity, val->val1, val->val2);
168
169 return 0;
170 } else {
171 return -ENOTSUP;
172 }
173 }
174
175 static DEVICE_API(sensor, si7006_api) = {
176 .sample_fetch = &si7006_sample_fetch,
177 .channel_get = &si7006_channel_get,
178 };
179
180 /**
181 * @brief initialize the sensor
182 *
183 * @return 0 for success
184 */
185
si7006_init(const struct device * dev)186 static int si7006_init(const struct device *dev)
187 {
188 const struct si7006_config *config = dev->config;
189
190 if (!device_is_ready(config->i2c.bus)) {
191 LOG_ERR("Bus device is not ready");
192 return -ENODEV;
193 }
194
195 LOG_DBG("si7006 init ok");
196
197 return 0;
198 }
199
200 #define SI7006_DEFINE(inst, name, temp_cmd) \
201 static struct si7006_data si7006_data_##name##_##inst; \
202 \
203 static const struct si7006_config si7006_config_##name##_##inst = { \
204 .i2c = I2C_DT_SPEC_INST_GET(inst), \
205 .read_temp_cmd = temp_cmd, \
206 }; \
207 \
208 SENSOR_DEVICE_DT_INST_DEFINE(inst, si7006_init, NULL, \
209 &si7006_data_##name##_##inst, \
210 &si7006_config_##name##_##inst, \
211 POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY, \
212 &si7006_api);
213
214 #define DT_DRV_COMPAT silabs_si7006
215 DT_INST_FOREACH_STATUS_OKAY_VARGS(SI7006_DEFINE, DT_DRV_COMPAT, SI7006_READ_OLD_TEMP);
216
217 #undef DT_DRV_COMPAT
218 #define DT_DRV_COMPAT sensirion_sht21
219 DT_INST_FOREACH_STATUS_OKAY_VARGS(SI7006_DEFINE, DT_DRV_COMPAT, SI7006_MEAS_TEMP_MASTER_MODE);
220
