Silicon Labs Si7021-A20 device driver: I2C Humidity and Temperature Sensor
Revision 1:344923bddd4f, committed 2017-09-14
- Comitter:
- ninensei
- Date:
- Thu Sep 14 00:16:02 2017 +0000
- Parent:
- 0:9909c9c7d326
- Commit message:
- Converted to template so that I2C driver derivations can be used (I2C, SoftI2C, etc...); Changed filename to match class name.
Changed in this revision
diff -r 9909c9c7d326 -r 344923bddd4f SI7021.h
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/SI7021.h Thu Sep 14 00:16:02 2017 +0000
@@ -0,0 +1,143 @@
+/* mbed Microcontroller Library
+ * Copyright (c) 2017 AT&T, IIoT Foundry, Plano, TX, USA
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/** \addtogroup drivers */
+
+/** Support for Silicon Labs SI7021 temperature and humidity sensor
+ *
+ * Example:
+ * @code
+ *
+ * #include "mbed.h"
+ * #include "SI7021.h"
+ *
+ * I2C i2c(I2C_SDA, I2C_SCL);
+ * SI7021<I2C> si7021(&i2c);
+ *
+ * int main() {
+ * si7021_measurements_t data;
+ * bool ok;
+ *
+ * ok = si7021->read(&data);
+ *
+ * if (ok) {
+ * printf("%%RelHum: %f\r\n", data.humidity_PR);
+ * printf("temp C/F: %f/%f\r\n", data.temp_C, data.temp_C * 9 / 5 + 32);
+ * } else {
+ * printf("si7021 error!\r\n");
+ * }
+ * }
+ * @endcode
+ * @ingroup drivers
+ */
+
+#pragma once
+
+#define SI7021A20_I2C_ADDR 0x80
+
+#define SI7021A20_CMD_MEAS_RH_HMM 0xE5
+#define SI7021A20_CMD_MEAS_RH_NHMM 0xF5
+#define SI7021A20_CMD_MEAS_TEMP_HMM 0xE3
+#define SI7021A20_CMD_MEAS_TEMP_NHMM 0xF3
+#define SI7021A20_CMD_READ_TEMP 0xE0
+#define SI7021A20_CMD_RESET 0xFE
+#define SI7021A20_CMD_WRITE_USER1 0xE6
+#define SI7021A20_CMD_WRITE_USER2 0xE7
+#define SI7021A20_CMD_WRITE_HEAT_CTRL 0x51
+#define SI7021A20_CMD_READ_HEAT_CTRL 0x11
+#define SI7021A20_CMD_READ_ID1 0xFA0F
+#define SI7021A20_CMD_READ_ID2 0xFCC9
+#define SI7021A20_REGF_ID2_DEV_ID 0x15
+#define SI7021A20_CMD_READ_FW_REV 0x84B8
+
+typedef struct {
+ float temp_C;
+ float humidity_PR;
+} si7021_measurements_t;
+
+template <class T>
+class SI7021 {
+ public:
+ /**
+ * Constructor
+ *
+ * @param i2c I2C class servicing the strip
+ */
+ SI7021(T * i2c) : _i2c(i2c) {}
+
+ /**
+ * Read temperature and humidity
+ *
+ * @param data points to struct to store measurements in. Stucture is
+ * valid only when function returns success indication.
+ *
+ * @returns true (success) or false (failure)
+ */
+ bool read(si7021_measurements_t * data) {
+ bool ok;
+ union {
+ char cmd;
+ struct {
+ uint8_t meas_msb;
+ uint8_t meas_lsb;
+ };
+ } buff;
+
+ buff.cmd = SI7021A20_CMD_MEAS_RH_HMM;
+ ok = (_i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2));
+ if (ok) {
+ // Humidity% = measurement * 125/65536 - 6
+ int meas_raw = ((int)buff.meas_msb << 8) + buff.meas_lsb;
+ data->humidity_PR = (float)meas_raw * (125.0F/65536.0F) - 6.0F;
+
+ buff.cmd = SI7021A20_CMD_READ_TEMP;
+ ok = _i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2);
+ }
+ if (ok) {
+ // TempC = measurement * 175.72/65536 - 46.85
+ int meas_raw = ((int)buff.meas_msb << 8) + buff.meas_lsb;
+ data->temp_C = meas_raw * (175.72/65536.0) - 46.85;
+ }
+ return ok;
+ }
+
+ protected:
+
+ /**
+ * I2C read/write helper function
+ *
+ * @param address is the register to read/write
+ * @param buff holds the data to write and recieves the data to read
+ * @param writeSize is the number of bytes to write to register
+ * @param readSize is the number of bytes to retrieve from device
+ *
+ * @returns true (success) or false (failure)
+ */
+ bool _i2c_transfer(int address, void * buff, size_t writeSize, size_t readSize) {
+ bool ok;
+ bool expect_response = (readSize != 0);
+
+ ok = !_i2c->write(address, (char*)buff, writeSize, expect_response);
+ if (ok && expect_response)
+ ok = !_i2c->read(address, (char*)buff, readSize);
+
+ return ok;
+ }
+
+
+ T *_i2c;
+};
+
diff -r 9909c9c7d326 -r 344923bddd4f si7021.cpp
--- a/si7021.cpp Tue Sep 12 17:17:03 2017 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,80 +0,0 @@
-#include "si7021.h"
-
-#define SI7021A20_I2C_ADDR 0x80
-
-#define SI7021A20_CMD_MEAS_RH_HMM 0xE5
-#define SI7021A20_CMD_MEAS_RH_NHMM 0xF5
-#define SI7021A20_CMD_MEAS_TEMP_HMM 0xE3
-#define SI7021A20_CMD_MEAS_TEMP_NHMM 0xF3
-#define SI7021A20_CMD_READ_TEMP 0xE0
-#define SI7021A20_CMD_RESET 0xFE
-#define SI7021A20_CMD_WRITE_USER1 0xE6
-#define SI7021A20_CMD_WRITE_USER2 0xE7
-#define SI7021A20_CMD_WRITE_HEAT_CTRL 0x51
-#define SI7021A20_CMD_READ_HEAT_CTRL 0x11
-#define SI7021A20_CMD_READ_ID1 0xFA0F
-#define SI7021A20_CMD_READ_ID2 0xFCC9
-#define SI7021A20_REGF_ID2_DEV_ID 0x15
-#define SI7021A20_CMD_READ_FW_REV 0x84B8
-
-bool SI7021::_i2c_transfer(int address, void * buff, size_t write_size, size_t read_size)
-{
- bool ok;
- bool expect_response = (read_size != 0);
-
- ok = !_i2c->write(address, (char*)buff, write_size, expect_response);
- if (ok && expect_response)
- ok = !_i2c->read(address, (char*)buff, read_size);
-
- return ok;
-}
-
-/*
-bool SI7021::_validate(void)
-{
- bool ok;
- uint8_t buff[4];
-
- buff[0] = (uint8_t)(SI7021A20_CMD_READ_ID2 >> 8);
- buff[1] = (uint8_t)(SI7021A20_CMD_READ_ID2);
-
- ok = (i2c_transfer(SI7021A20_I2C_ADDR, buff, 2, 1)) &&
- (SI7021A20_REGF_ID2_DEV_ID == buff[0]);
-
- return ok;
-}
-*/
-
-bool SI7021::read(si7021_measurements_t * data) {
- bool ok;
- union {
- char cmd;
- struct {
- uint8_t meas_msb;
- uint8_t meas_lsb;
- };
- } buff;
-
- buff.cmd = SI7021A20_CMD_MEAS_RH_HMM;
- ok = (_i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2));
- if (ok) {
- // Humidity% = measurement * 125/65536 - 6
- int meas_raw = ((int)buff.meas_msb << 8) + buff.meas_lsb;
- data->humidity_PR = (float)meas_raw * (125.0F/65536.0F) - 6.0F;
-// data->humidity = meas_raw / 2 - 1573;
-// data->humidity_norm = 262;
-// printf("<humidityH/r = %f/%d>", Humidity, meas_raw);
-
- buff.cmd = SI7021A20_CMD_READ_TEMP;
- ok = _i2c_transfer(SI7021A20_I2C_ADDR, &buff, 1, 2);
- }
- if (ok) {
- // TempC = measurement * 175.72/65536 - 46.85
- int meas_raw = ((int)buff.meas_msb << 8) + buff.meas_lsb;
- data->temp_C = meas_raw * (175.72/65536.0) - 46.85;
-// data->temp = meas_raw / 2 - 8736;
-// data->temp_norm = 186;
-// printf("<tempC/F/r = %f/%f/%d>", Temp, Temp * 9 / 5 + 32, meas_raw);
- }
- return ok;
-}
diff -r 9909c9c7d326 -r 344923bddd4f si7021.h
--- a/si7021.h Tue Sep 12 17:17:03 2017 +0000
+++ /dev/null Thu Jan 01 00:00:00 1970 +0000
@@ -1,56 +0,0 @@
-#include "mbed.h"
-
-#ifndef SI7021_H
-#define SI7021_H
-
-typedef struct {
- float temp_C;
- float humidity_PR;
-// int16_t temp;
-// int16_t temp_norm;
-// int16_t humidity;
-// int16_t humidity_norm;
-} si7021_measurements_t;
-
-class SI7021 {
- public:
- /**
- * Constructor
- *
- * @param i2c I2C class servicing the strip
- */
- SI7021(I2C * i2c) : _i2c(i2c) {}
-
- /**
- * Read temperature and humidity
- *
- * @param data points to struct to store measurements in. Stucture is
- * valid only when function returns success indication.
- *
- * @returns true (success) or false (failure)
- */
- bool read(si7021_measurements_t * data);
-
- protected:
-
- /**
- * I2C read/write helper function
- *
- * @param address is the register to read/write
- * @param buff holds the data to write and recieves the data to read
- * @param writeSize is the number of bytes to write to register
- * @param readSize is the number of bytes to retrieve from device
- *
- * @returns true (success) or false (failure)
- */
- bool _i2c_transfer(int address, void * buff, size_t writeSize, size_t readSize);
-
- /**
- *
- bool _validate(void)
- */
-
- I2C *_i2c;
-};
-
-#endif //SI7021_H