Si7020 Device Driver

Diff: Si7020.cpp

Revision:

0:9a1febb56203

Child:

1:eca9d19c17ab

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Si7020.cpp	Fri Apr 17 09:53:45 2015 -0500
@@ -0,0 +1,424 @@
+/*******************************************************************************
+ * Copyright (C) 2015 Maxim Integrated Products, Inc., All Rights Reserved.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included
+ * in all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+ * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+ * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+ * IN NO EVENT SHALL MAXIM INTEGRATED BE LIABLE FOR ANY CLAIM, DAMAGES
+ * OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ * ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+ * OTHER DEALINGS IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the name of Maxim Integrated
+ * Products, Inc. shall not be used except as stated in the Maxim Integrated
+ * Products, Inc. Branding Policy.
+ *
+ * The mere transfer of this software does not imply any licenses
+ * of trade secrets, proprietary technology, copyrights, patents,
+ * trademarks, maskwork rights, or any other form of intellectual
+ * property whatsoever. Maxim Integrated Products, Inc. retains all
+ * ownership rights.
+ *******************************************************************************
+ */
+
+#include "Si7020.h"
+
+/***** Definitions *****/
+#define I2C_ADDR    (0x80)  // 1000000x
+#define POLYVAL     (0x131)
+
+/***** File Scope Data *****/
+static const char cmd_meas_humid[] = { 0xE5 };
+static const char cmd_meas_humid_no_hold[] = { 0xF5 };
+static const char cmd_meas_temp[] = { 0xE3 };
+static const char cmd_meas_temp_no_hold[] = { 0xF3 };
+static const char cmd_meas_prev_temp[] = { 0xE0 };
+static const char cmd_rst[] = { 0xFE };
+static const char cmd_write_user1[] = { 0xE6 };
+static const char cmd_read_user1[] = { 0xE7 };
+static const char cmd_id_1[] = { 0xFA, 0x0F };
+static const char cmd_id_2[] = { 0xFC, 0xC9 };
+static const char cmd_fw_ver[] = { 0x84, 0xB8 };
+
+//******************************************************************************
+Si7020::Si7020(PinName sda, PinName scl)
+{
+    i2c_ = new I2C(sda, scl);
+    i2c_owner = true;
+
+    // 400KHz, as specified by the datasheet.
+    i2c_->frequency(400000);
+}
+
+//******************************************************************************
+Si7020::Si7020(I2C *i2c) :
+    i2c_(i2c)
+{
+    i2c_owner = false;
+}
+
+//******************************************************************************
+Si7020::~Si7020()
+{
+    if(i2c_owner) {
+        delete i2c_;
+    }
+}
+
+//******************************************************************************
+int Si7020::reset(void)
+{
+    if (i2c_->write(I2C_ADDR, cmd_rst, sizeof(cmd_rst)) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getElectronicId(char* id)
+{
+    // Send cmd with repeated start
+    if (i2c_->write(I2C_ADDR, cmd_id_1, sizeof(cmd_id_1), true) != 0) {
+        return -1;
+    }
+
+    // Read first portion of ID
+    char temp[8];
+    if (i2c_->read(I2C_ADDR, temp, 8, false) != 0) {
+        return -1;
+    }
+
+    // Check the CRC
+    char crc = 0;
+    int i;
+    for(i = 0; i < 4; i++) {
+        crc = crc8(temp[2*i], crc);
+        if(crc != temp[2*i +1]) {
+            return -1;
+        }
+    }
+
+    // Save top portion of ID
+    id[7] = temp [0];
+    id[6] = temp [2];
+    id[5] = temp [4];
+    id[4] = temp [6];
+
+    // Send cmd with repeated start
+    if (i2c_->write(I2C_ADDR, cmd_id_2, sizeof(cmd_id_2), true) != 0) {
+        return -1;
+    }
+
+    // Read rest of ID
+    if (i2c_->read(I2C_ADDR, temp, 6, false) != 0) {
+        return -1;
+    }
+
+    // Check the CRC
+    crc = 0;
+    for(i = 0; i < 2; i++) {
+        crc = crc8(temp[3*i], crc);
+        crc = crc8(temp[3*i + 1], crc);
+        if(crc != temp[3*i + 2]) {
+            return -1;
+        }
+    }
+
+    // Save bottom portion of ID
+    id[3] = temp [0];
+    id[2] = temp [1];
+    id[1] = temp [3];
+    id[0] = temp [4];
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::configResolution(Si7020::resolution_t resolution)
+{
+    char data[2];
+
+    if (i2c_->write(I2C_ADDR, cmd_read_user1, sizeof(cmd_read_user1)) != 0) {
+        return -1;
+    }
+
+    if (i2c_->read(I2C_ADDR, &data[1], 1) != 0) {
+        return -1;
+    }
+
+    switch (resolution) {
+        case RH_12b_TEMP_14b:
+            data[1] &= ~0x81;
+            break;
+        case RH_8b_TEMP_12b:
+            data[1] = (data[1] & ~0x80) | 0x01;
+            break;
+        case RH_10b_TEMP_13b:
+            data[1] = (data[1] & ~0x01) | 0x80;
+            break;
+        case RH_11b_TEMP_11b:
+            data[1] |= 0x81;
+            break;
+        default:
+            return -1;
+    }
+
+    data[0] = cmd_write_user1[0];
+
+    if (i2c_->write(I2C_ADDR, data, 2) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getTemperature(int16_t *tempCx10)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_temp, sizeof(cmd_meas_temp)) != 0) {
+        return -1;
+    }
+
+    return checkTemperature(tempCx10);
+}
+
+//******************************************************************************
+int Si7020::getTemperature(float *tempC)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_temp, sizeof(cmd_meas_temp)) != 0) {
+        return -1;
+    }
+
+    return checkTemperature(tempC);
+}
+
+//******************************************************************************
+int Si7020::startTemperature(void)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_temp_no_hold, sizeof(cmd_meas_temp_no_hold)) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::checkTemperature(int16_t *tempCx10)
+{
+    char data[3];
+    uint16_t code;
+    int temp;
+
+    if (i2c_->read(I2C_ADDR, data, 3) != 0) {
+        return -1;
+    }
+
+    // Get 16-bit value from bytes read
+    code = ((uint16_t)data[0] << 8) + data[1];
+
+    // Calculate the temperature using the formula from the datasheet
+    // Scaled by 100
+    temp = ((((int)17572 * code) + 0x8000) >> 16) - 4685;
+
+    // Return value is to be scaled by 10
+    *tempCx10 = (temp + 5) / 10;
+    
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::checkTemperature(float *tempC)
+{
+    char data[3];
+    uint16_t code;
+
+    if (i2c_->read(I2C_ADDR, data, 3) != 0) {
+        return -1;
+    }
+
+    // Get 16-bit value from bytes read
+    code = ((uint16_t)data[0] << 8) + data[1];
+
+    // Calculate the temperature using the formula from the datasheet
+    // Scaled by 100
+    *tempC = (((float)175.72 * code) / 65536) - 46.85;
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getHumidity(int16_t *humidx10)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_humid, sizeof(cmd_meas_humid), true) != 0) {
+        return -1;
+    }
+
+    return checkHumidity(humidx10);
+}
+
+//******************************************************************************
+int Si7020::getHumidity(float *humid)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_humid, sizeof(cmd_meas_humid)) != 0) {
+        return -1;
+    }
+
+    return checkHumidity(humid);
+}
+
+//******************************************************************************
+int Si7020::startHumidity(void)
+{
+    if (i2c_->write(I2C_ADDR, cmd_meas_humid_no_hold, sizeof(cmd_meas_humid_no_hold)) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::checkHumidity(int16_t *humidx10)
+{
+    char data[3];
+    uint16_t code;
+
+    if (i2c_->read(I2C_ADDR, data, 3) != 0) {
+        return -1;
+    }
+
+    // Get 16-bit value from bytes read
+    code = ((uint16_t)data[0] << 8) + data[1];
+
+    // Calculate the humidity using the formula from the datasheet
+    // Scaled by 10
+    *humidx10 = ((((int)1250 * code) + 0x8000) >> 16) - 60;
+
+    // Check the crc
+    char crc = crc8(data[0], 0x00);
+    crc = crc8(data[1], crc);
+    if(crc != data[2]) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::checkHumidity(float *humid)
+{
+    char data[3];
+    uint16_t code;
+
+    if (i2c_->read(I2C_ADDR, data, 3) != 0) {
+        return -1;
+    }
+
+    // Get 16-bit value from bytes read
+    code = ((uint16_t)data[0] << 8) + data[1];
+
+    // Calculate the humidity using the formula from the datasheet
+    *humid = (((float)125 * code) / 65536) - 6;
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getPrevTemperature(float *tempC) {
+
+    if (i2c_->write(I2C_ADDR, cmd_meas_prev_temp, sizeof(cmd_meas_prev_temp)) != 0) {
+        return -1;
+    }
+
+    if(checkTemperature(tempC) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getPrevTemperature(int16_t *tempCx10) {
+
+    if (i2c_->write(I2C_ADDR, cmd_meas_prev_temp, sizeof(cmd_meas_prev_temp)) != 0) {
+        return -1;
+    }
+
+    if(checkTemperature(tempCx10) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::getRev(char *rev)
+{
+    if (i2c_->write(I2C_ADDR, cmd_fw_ver, sizeof(cmd_fw_ver)) != 0) {
+        return -1;
+    }
+
+    if (i2c_->read(I2C_ADDR, rev, 1) != 0) {
+        return -1;
+    }
+    
+    return 0;
+}
+
+//******************************************************************************
+int Si7020::heater(bool enable)
+{
+    char data[2];
+
+    if (i2c_->write(I2C_ADDR, cmd_read_user1, sizeof(cmd_read_user1)) != 0) {
+        return -1;
+    }
+
+    if (i2c_->read(I2C_ADDR, &data[1], 1) != 0) {
+        return -1;
+    }
+
+    if (enable) {
+        data[1] |= 0x04;
+    } else {
+        data[1] &= ~0x04;
+    }
+
+    data[0] = cmd_write_user1[0];
+
+    if (i2c_->write(I2C_ADDR, data, 2) != 0) {
+        return -1;
+    }
+
+    return 0;
+}
+
+//******************************************************************************
+char Si7020::crc8(char value, char seed)
+{
+    int i;
+
+    for (i = 0; i < 8; i++) {
+
+        if ((value ^ seed) & 0x80) {
+            seed <<= 1;
+            seed ^= POLYVAL;
+        } else {
+            seed <<= 1;
+        }
+
+        value <<= 1;
+    }
+
+    return seed;
+}