+/**\mainpage
+ * Copyright (C) 2016 - 2017 Bosch Sensortec GmbH
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are met:
+ *
+ * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *
+ * Redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution.
+ *
+ * Neither the name of the copyright holder nor the names of the
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
+ * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
+ * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ * DISCLAIMED. IN NO EVENT SHALL COPYRIGHT HOLDER
+ * OR CONTRIBUTORS BE LIABLE FOR ANY
+ * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY,
+ * OR CONSEQUENTIAL DAMAGES(INCLUDING, BUT NOT LIMITED TO,
+ * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
+ * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
+ * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
+ * ANY WAY OUT OF THE USE OF THIS
+ * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE
+ *
+ * The information provided is believed to be accurate and reliable.
+ * The copyright holder assumes no responsibility
+ * for the consequences of use
+ * of such information nor for any infringement of patents or
+ * other rights of third parties which may result from its use.
+ * No license is granted by implication or otherwise under any patent or
+ * patent rights of the copyright holder.
+ *
+ * File bme280_selftest.c
+ * Date 21 Nov 2017
+ * Version 1.0.0
+ *
+ */
+
+#include "bme280_selftest.h"
+
+#define BME280_CRC_DATA_ADDR UINT8_C(0xE8)
+#define BME280_CRC_DATA_LEN UINT8_C(1)
+#define BME280_CRC_CALIB1_ADDR UINT8_C(0x88)
+#define BME280_CRC_CALIB1_LEN UINT8_C(26)
+#define BME280_CRC_CALIB2_ADDR UINT8_C(0xE1)
+#define BME280_CRC_CALIB2_LEN UINT8_C(7)
+
+/*!
+ * @brief This API calculates the CRC
+ *
+ * @param[in] mem_values : reg_data parameter to calculate CRC
+ * @param[in] mem_length : Parameter to calculate CRC
+ *
+ * @return Result of API execution status
+ * @retval zero -> Success / +ve value -> Warning / -ve value -> Error
+ */
+static uint8_t crc_calculate(uint8_t *mem_values, uint8_t mem_length);
+
+/*!
+ * @brief This API reads the stored CRC and then compare with calculated CRC
+ *
+ * @param[in] dev : Structure instance of bme280_dev.
+ *
+ * @return Result of API execution status
+ * @retval zero -> self test success / +ve value -> warning(self test fail)
+ */
+int8_t bme280_crc_selftest(const struct bme280_dev *dev)
+{
+ int8_t rslt;
+ uint8_t reg_addr;
+ uint8_t reg_data[64];
+
+ uint8_t stored_crc = 0;
+ uint8_t calculated_crc = 0;
+
+ /* Read stored crc value from register */
+ reg_addr = BME280_CRC_DATA_ADDR;
+ rslt = bme280_get_regs(reg_addr, reg_data, BME280_CRC_DATA_LEN, dev);
+ if (rslt == BME280_OK) {
+ stored_crc = reg_data[0];
+ /* Calculated CRC value with calibration register */
+ reg_addr = BME280_CRC_CALIB1_ADDR;
+ rslt = bme280_get_regs(reg_addr, ®_data[0], BME280_CRC_CALIB1_LEN, dev);
+ if (rslt == BME280_OK) {
+ reg_addr = BME280_CRC_CALIB2_ADDR;
+ rslt = bme280_get_regs(reg_addr, ®_data[BME280_CRC_CALIB1_LEN], BME280_CRC_CALIB2_LEN, dev);
+ if (rslt == BME280_OK) {
+ calculated_crc = crc_calculate(reg_data, BME280_CRC_CALIB1_LEN + BME280_CRC_CALIB2_LEN);
+ /* Validate CRC */
+ if (stored_crc == calculated_crc)
+ rslt = BME280_OK;
+ else
+ rslt = BME280_W_SELF_TEST_FAIL;
+ }
+ }
+ }
+
+ return rslt;
+}
+
+/*!
+ * @brief This API calculates the CRC
+ *
+ * @param[in] mem_values : reg_data parameter to calculate CRC
+ * @param[in] mem_length : Parameter to calculate CRC
+ *
+ * @return Result of API execution status
+ * @retval zero -> Success / +ve value -> Warning / -ve value -> Error
+ */
+static uint8_t crc_calculate(uint8_t *mem_values, uint8_t mem_length)
+{
+ uint32_t crc_reg = 0xFF;
+ uint8_t polynomial = 0x1D;
+ uint8_t bitNo, index;
+ uint8_t din = 0;
+
+ for (index = 0; index < mem_length; index++) {
+ for (bitNo = 0; bitNo < 8; bitNo++) {
+ if (((crc_reg & 0x80) > 0) ^ ((mem_values[index] & 0x80) > 0))
+ din = 1;
+ else
+ din = 0;
+
+ /* Truncate 8th bit for crc_reg and mem_values */
+ crc_reg = (uint32_t)((crc_reg & 0x7F) << 1);
+ mem_values[index] = (uint8_t)((mem_values[index] & 0x7F) << 1);
+ crc_reg = (uint32_t)(crc_reg ^ (polynomial * din));
+ }
+ }
+
+ return (uint8_t)(crc_reg ^ 0xFF);
+}