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/regulator.h>
11 #include <zephyr/drivers/sensor.h>
12 #include <zephyr/kernel.h>
13 #include <zephyr/sys/byteorder.h>
14 #include <zephyr/sys/__assert.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 const struct device *vin_supply;
31 /** Use "read temp" vs "read old temp" command, the latter only with SiLabs sensors. */
32 uint8_t read_temp_cmd;
33 };
34
35 /**
36 * @brief function to get relative humidity
37 *
38 * @return int 0 on success
39 */
si7006_get_humidity(const struct device * dev)40 static int si7006_get_humidity(const struct device *dev)
41 {
42 struct si7006_data *si_data = dev->data;
43 const struct si7006_config *config = dev->config;
44 int retval;
45 uint16_t hum;
46
47 retval = i2c_burst_read_dt(&config->i2c, SI7006_MEAS_REL_HUMIDITY_MASTER_MODE,
48 (uint8_t *)&hum, sizeof(hum));
49
50 if (retval == 0) {
51 si_data->humidity = sys_be16_to_cpu(hum) & ~3;
52 } else {
53 LOG_ERR("read register err: %d", retval);
54 }
55
56 return retval;
57 }
58
59 /**
60 * @brief function to get temperature
61 *
62 * Note that for Si7006 type sensors, si7006_get_humidity must be called before
63 * calling si7006_get_temperature, as the get old temperature command is used.
64 *
65 * @return int 0 on success
66 */
67
si7006_get_temperature(const struct device * dev)68 static int si7006_get_temperature(const struct device *dev)
69 {
70 struct si7006_data *si_data = dev->data;
71 const struct si7006_config *config = dev->config;
72 uint16_t temp;
73 int retval;
74
75 retval = i2c_burst_read_dt(&config->i2c, config->read_temp_cmd,
76 (uint8_t *)&temp, sizeof(temp));
77
78 if (retval == 0) {
79 si_data->temperature = sys_be16_to_cpu(temp) & ~3;
80 } else {
81 LOG_ERR("read register err: %d", retval);
82 }
83
84 return retval;
85 }
86
87 /**
88 * @brief fetch a sample from the sensor
89 *
90 * @return 0
91 */
si7006_sample_fetch(const struct device * dev,enum sensor_channel chan)92 static int si7006_sample_fetch(const struct device *dev,
93 enum sensor_channel chan)
94 {
95 int retval;
96
97 retval = si7006_get_humidity(dev);
98 if (retval == 0) {
99 retval = si7006_get_temperature(dev);
100 }
101
102 return retval;
103 }
104
105 /**
106 * @brief sensor value get
107 *
108 * @return -ENOTSUP for unsupported channels
109 */
si7006_channel_get(const struct device * dev,enum sensor_channel chan,struct sensor_value * val)110 static int si7006_channel_get(const struct device *dev,
111 enum sensor_channel chan,
112 struct sensor_value *val)
113 {
114 struct si7006_data *si_data = dev->data;
115
116 if (chan == SENSOR_CHAN_AMBIENT_TEMP) {
117 /* Raw formula: (temp * 175.72) / 65536 - 46.85
118 * To use integer math, scale the 175.72 factor by 128 and move the offset to
119 * inside the division. This gives us:
120 *
121 * (temp * 175.72 * 128 - 46.86 * 128 * 65536) / (65536 * 128)
122 * The constants can be calculated now:
123 * (temp * 22492 - 393006285) / 2^23
124 *
125 * There is a very small amount of round-off error in the factor of 22492. To
126 * compenstate, a constant of 5246 is used to center the error about 0, thus
127 * reducing the overall MSE.
128 */
129
130 /* Temperature value times two to the 23rd power, i.e. temp_23 = temp << 23 */
131 const int32_t temp_23 = si_data->temperature * 22492 - (393006285 - 5246);
132 /* Integer component of temperature */
133 int32_t temp_int = temp_23 >> 23;
134 /* Fractional component of temperature */
135 int32_t temp_frac = temp_23 & BIT_MASK(23);
136
137 /* Deal with the split twos-complement / BCD format oddness with negatives */
138 if (temp_23 < 0) {
139 temp_int += 1;
140 temp_frac -= BIT(23);
141 }
142 val->val1 = temp_int;
143 /* Remove a constant factor of 64 from (temp_frac * 1000000) >> 23 */
144 val->val2 = (temp_frac * 15625ULL) >> 17;
145
146 LOG_DBG("temperature %u = val1:%d, val2:%d", si_data->temperature,
147 val->val1, val->val2);
148
149 return 0;
150 } else if (chan == SENSOR_CHAN_HUMIDITY) {
151 /* Humidity times two to the 16th power. Offset of -6 not applied yet. */
152 const uint32_t rh_16 = si_data->humidity * 125U;
153 /* Integer component of humidity */
154 const int16_t rh_int = rh_16 >> 16;
155 /* Fraction component of humidity */
156 const uint16_t rh_frac = rh_16 & BIT_MASK(16);
157
158 val->val1 = rh_int - 6; /* Apply offset now */
159 /* Remove a constant factor of 64 from (rh_frac * 1000000) >> 16 */
160 val->val2 = (rh_frac * 15625) >> 10;
161
162 /* Deal with the split twos-complement / BCD format oddness with negatives */
163 if (val->val1 < 0) {
164 val->val1 += 1;
165 val->val2 -= 1000000;
166 }
167
168 LOG_DBG("humidity %u = val1:%d, val2:%d", si_data->humidity, val->val1, val->val2);
169
170 return 0;
171 } else {
172 return -ENOTSUP;
173 }
174 }
175
176 static DEVICE_API(sensor, si7006_api) = {
177 .sample_fetch = &si7006_sample_fetch,
178 .channel_get = &si7006_channel_get,
179 };
180
181 /**
182 * @brief initialize the sensor
183 *
184 * @return 0 for success
185 */
186
si7006_init(const struct device * dev)187 static int si7006_init(const struct device *dev)
188 {
189 const struct si7006_config *config = dev->config;
190
191 if (!device_is_ready(config->i2c.bus)) {
192 LOG_ERR("Bus device is not ready");
193 return -ENODEV;
194 }
195
196 if (IS_ENABLED(CONFIG_REGULATOR) && config->vin_supply) {
197 regulator_enable(config->vin_supply);
198
199 /* As stated by the Si7006 spec - Maximum powerup time is 80ms */
200 k_msleep(80);
201 }
202
203 LOG_DBG("si7006 init ok");
204
205 return 0;
206 }
207
208 #define SI7006_DEFINE(inst, name, temp_cmd) \
209 static struct si7006_data si7006_data_##name##_##inst; \
210 \
211 static const struct si7006_config si7006_config_##name##_##inst = { \
212 .i2c = I2C_DT_SPEC_INST_GET(inst), \
213 .vin_supply = DEVICE_DT_GET_OR_NULL(DT_INST_PHANDLE(inst, vin_supply)), \
214 .read_temp_cmd = temp_cmd, \
215 }; \
216 \
217 SENSOR_DEVICE_DT_INST_DEFINE(inst, si7006_init, NULL, \
218 &si7006_data_##name##_##inst, \
219 &si7006_config_##name##_##inst, \
220 POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY, \
221 &si7006_api);
222
223 #define DT_DRV_COMPAT silabs_si7006
224 DT_INST_FOREACH_STATUS_OKAY_VARGS(SI7006_DEFINE, DT_DRV_COMPAT, SI7006_READ_OLD_TEMP);
225
226 #undef DT_DRV_COMPAT
227 #define DT_DRV_COMPAT sensirion_sht21
228 DT_INST_FOREACH_STATUS_OKAY_VARGS(SI7006_DEFINE, DT_DRV_COMPAT, SI7006_MEAS_TEMP_MASTER_MODE);
229
