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42 * File bme280_selftest.c
48 #include "bme280_selftest.h"
50 #define BME280_CRC_DATA_ADDR UINT8_C(0xE8)
51 #define BME280_CRC_DATA_LEN UINT8_C(1)
52 #define BME280_CRC_CALIB1_ADDR UINT8_C(0x88)
53 #define BME280_CRC_CALIB1_LEN UINT8_C(26)
54 #define BME280_CRC_CALIB2_ADDR UINT8_C(0xE1)
55 #define BME280_CRC_CALIB2_LEN UINT8_C(7)
58 * @brief This API calculates the CRC
60 * @param[in] mem_values : reg_data parameter to calculate CRC
61 * @param[in] mem_length : Parameter to calculate CRC
63 * @return Result of API execution status
64 * @retval zero -> Success / +ve value -> Warning / -ve value -> Error
66 static uint8_t crc_calculate(uint8_t *mem_values, uint8_t mem_length);
69 * @brief This API reads the stored CRC and then compare with calculated CRC
71 * @param[in] dev : Structure instance of bme280_dev.
73 * @return Result of API execution status
74 * @retval zero -> self test success / +ve value -> warning(self test fail)
76 int8_t bme280_crc_selftest(const struct bme280_dev *dev)
81 uint8_t stored_crc = 0;
82 uint8_t calculated_crc = 0;
84 /* Read stored crc value from register */
85 reg_addr = BME280_CRC_DATA_ADDR;
86 rslt = bme280_get_regs(reg_addr, reg_data, BME280_CRC_DATA_LEN, dev);
87 if (rslt == BME280_OK)
89 stored_crc = reg_data[0];
91 /* Calculated CRC value with calibration register */
92 reg_addr = BME280_CRC_CALIB1_ADDR;
93 rslt = bme280_get_regs(reg_addr, ®_data[0], BME280_CRC_CALIB1_LEN, dev);
94 if (rslt == BME280_OK)
96 reg_addr = BME280_CRC_CALIB2_ADDR;
97 rslt = bme280_get_regs(reg_addr, ®_data[BME280_CRC_CALIB1_LEN], BME280_CRC_CALIB2_LEN, dev);
98 if (rslt == BME280_OK)
100 calculated_crc = crc_calculate(reg_data, BME280_CRC_CALIB1_LEN + BME280_CRC_CALIB2_LEN);
103 if (stored_crc == calculated_crc)
109 rslt = BME280_W_SELF_TEST_FAIL;
119 * @brief This API calculates the CRC
121 * @param[in] mem_values : reg_data parameter to calculate CRC
122 * @param[in] mem_length : Parameter to calculate CRC
124 * @return Result of API execution status
125 * @retval zero -> Success / +ve value -> Warning / -ve value -> Error
127 static uint8_t crc_calculate(uint8_t *mem_values, uint8_t mem_length)
129 uint32_t crc_reg = 0xFF;
130 uint8_t polynomial = 0x1D;
131 uint8_t bitNo, index;
134 for (index = 0; index < mem_length; index++)
136 for (bitNo = 0; bitNo < 8; bitNo++)
138 if (((crc_reg & 0x80) > 0) != ((mem_values[index] & 0x80) > 0))
147 /* Truncate 8th bit for crc_reg and mem_values */
148 crc_reg = (uint32_t)((crc_reg & 0x7F) << 1);
149 mem_values[index] = (uint8_t)((mem_values[index] & 0x7F) << 1);
150 crc_reg = (uint32_t)(crc_reg ^ (polynomial * din));
154 return (uint8_t)(crc_reg ^ 0xFF);