91 lines
2.3 KiB
C
91 lines
2.3 KiB
C
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/**
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* @file
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* The main code of the zh_ds18b20 component.
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*
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*/
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#include "zh_ds18b20.h"
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/// \cond
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#define SCRATCHPAD_LENGTH 8 // Scratchpad length.
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#define CONVERT_TEMPERATURE 0x44 // Initiates temperature conversion.
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#define READ_SCRATCHPAD 0xBE // Reads bytes from scratchpad.
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#define pgm_read_byte(addr) (*(const uint8_t *)(addr))
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/// \endcond
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static uint8_t _crc_calculate(const uint8_t *scratchpad);
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static const char *TAG = "zh_ds18b20";
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static const uint8_t _crc_table[] = {
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0x00, 0x5E, 0xBC, 0xE2, 0x61, 0x3F, 0xDD, 0x83,
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0xC2, 0x9C, 0x7E, 0x20, 0xA3, 0xFD, 0x1F, 0x41,
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0x00, 0x9D, 0x23, 0xBE, 0x46, 0xDB, 0x65, 0xF8,
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0x8C, 0x11, 0xAF, 0x32, 0xCA, 0x57, 0xE9, 0x74};
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esp_err_t zh_ds18b20_read(const uint8_t *device, float *temperature)
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{
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ESP_LOGI(TAG, "DS18B20 read begin.");
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uint8_t scratchpad[9];
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if (device == NULL)
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{
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if (zh_onewire_skip_rom() != ESP_OK)
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{
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ESP_LOGE(TAG, "DS18B20 read fail.");
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return ESP_FAIL;
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}
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}
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else
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{
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if (zh_onewire_match_rom(device) != ESP_OK)
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{
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ESP_LOGE(TAG, "DS18B20 read fail.");
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return ESP_FAIL;
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}
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}
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zh_onewire_send_byte(CONVERT_TEMPERATURE);
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vTaskDelay(750 / portTICK_PERIOD_MS);
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if (device == NULL)
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{
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if (zh_onewire_skip_rom() != ESP_OK)
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{
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ESP_LOGE(TAG, "DS18B20 read fail.");
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return ESP_FAIL;
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}
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}
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else
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{
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if (zh_onewire_match_rom(device) != ESP_OK)
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{
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ESP_LOGE(TAG, "DS18B20 read fail.");
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return ESP_FAIL;
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}
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}
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zh_onewire_send_byte(READ_SCRATCHPAD);
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for (uint8_t i = 0; i < 9; ++i)
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{
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scratchpad[i] = zh_onewire_read_byte();
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}
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if (scratchpad[8] != _crc_calculate(scratchpad))
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{
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ESP_LOGE(TAG, "DS18B20 read fail. Invalid CRC.");
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return ESP_ERR_INVALID_CRC;
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}
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*temperature = (float)(scratchpad[0] + (scratchpad[1] * 256)) / 16;
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ESP_LOGI(TAG, "DS18B20 read success.");
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return ESP_OK;
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}
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static uint8_t _crc_calculate(const uint8_t *scratchpad)
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{
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uint8_t crc = 0;
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uint8_t length = SCRATCHPAD_LENGTH;
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while (length--)
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{
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crc = *scratchpad++ ^ crc;
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crc = pgm_read_byte(_crc_table + (crc & 0x0f)) ^ pgm_read_byte(_crc_table + 16 + ((crc >> 4) & 0x0f));
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}
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return crc;
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}
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