2  * Copyright (c) 2022 HAW Hamburg FTZ-DIWIP
4  * SPDX-License-Identifier: Apache-2.0
10 	const struct max31865_config *cfg = dev->config;  in max31865_spi_write()
18 	const struct spi_buf_set tx = {.buffers = bufs, .count = 2};  in max31865_spi_write()
20 	return spi_write_dt(&cfg->spi, &tx);  in max31865_spi_write()
25 	const struct max31865_config *cfg = dev->config;  in max31865_spi_read()
29 	const struct spi_buf_set tx = {.buffers = &tx_buf, .count = 1};  in max31865_spi_read()
35 	const struct spi_buf_set rx = {.buffers = rx_buf, .count = 2};  in max31865_spi_read()
37 	return spi_transceive_dt(&cfg->spi, &tx, &rx);  in max31865_spi_read()
48 	struct max31865_data *data = dev->data;  in configure_device()
49 	uint8_t cmd[] = {data->config_control_bits};  in configure_device()
59  * @brief Set device fail threshold registers
66 	const struct max31865_config *config = dev->config;  in set_threshold_values()
68 		(config->high_threshold >> 7) & 0x00ff, (config->high_threshold << 1) & 0x00ff,  in set_threshold_values()
69 		(config->low_threshold >> 7) & 0x00ff, (config->low_threshold << 1) & 0x00ff};  in set_threshold_values()
81  * Apply the Callendar-Van Dusen equation to convert the RTD resistance
83  * Tr = (-A + SQRT(delta) ) / 2*B
84  * delta = A^2 - 4B*(1-Rt/Ro)
86  * https://www.analog.com/media/en/technical-documentation/application-notes/AN709_0.pdf
94 	double delta = (RTD_A * RTD_A) - 4 * RTD_B * (1.0 - resistance / resistance_0);  in calculate_temperature()
96 	temperature = (-RTD_A + sqrt(delta)) / (2 * RTD_B);  in calculate_temperature()
102 	temperature = RTD_C[0] + RTD_C[1] * resistance + RTD_C[2] * pow(resistance, 2) -  in calculate_temperature()
103 		      RTD_C[3] * pow(resistance, 3) - RTD_C[4] * pow(resistance, 4) +  in calculate_temperature()
111  * Apply a very good linear approximation of the Callendar-Van Dusen equation to convert the RTD
121 	temperature = (resistance - resistance_0) / (resistance_0 * RTD_A);  in calculate_temperature()
136 	struct max31865_data *data = dev->data;  in max31865_set_vbias()
138 	WRITE_BIT(data->config_control_bits, 7, enable);  in max31865_set_vbias()
144 	struct max31865_data *data = dev->data;  in max31865_set_three_wire()
146 	WRITE_BIT(data->config_control_bits, 4, enable);  in max31865_set_three_wire()
160 		return "RTDIN- < 0.85*VBIAS (FORCE- open)";  in max31865_error_to_string()
163 		return "REFIN- < 0.85*VBIAS (FORCE- open)";  in max31865_error_to_string()
166 		return "REFIN- > 0.85*VBIAS";  in max31865_error_to_string()
169 		return "RTD below low threshold";  in max31865_error_to_string()
172 		return "RTD above high threshold";  in max31865_error_to_string()
183 	struct max31865_data *data = dev->data;  in max31865_fault_register()
184 	saved_fault_bits  = data->config_control_bits & FAULT_BITS_CLEAR_MASK;  in max31865_fault_register()
186 	WRITE_BIT(data->config_control_bits, 1, 1);  in max31865_fault_register()
187 	data->config_control_bits &= ~FAULT_BITS_CLEAR_MASK;  in max31865_fault_register()
191 	WRITE_BIT(data->config_control_bits, 1, 0);  in max31865_fault_register()
192 	data->config_control_bits |= saved_fault_bits;  in max31865_fault_register()
222 		return -EIO;  in max31865_get_temperature()
229 		return -EIO;  in max31865_get_temperature()
232 	const struct max31865_config *config = dev->config;  in max31865_get_temperature()
233 	struct max31865_data *data = dev->data;  in max31865_get_temperature()
239 	resistance *= config->resistance_reference;  in max31865_get_temperature()
240 	data->temperature = calculate_temperature(resistance, config->resistance_at_zero);  in max31865_get_temperature()
246 	const struct max31865_config *config = dev->config;  in max31865_init()
248 	if (!spi_is_ready_dt(&config->spi)) {  in max31865_init()
249 		return -ENODEV;  in max31865_init()
251 	struct max31865_data *data = dev->data;  in max31865_init()
253 	data->config_control_bits = 0;  in max31865_init()
255 	WRITE_BIT(data->config_control_bits, 6, config->conversion_mode);  in max31865_init()
256 	WRITE_BIT(data->config_control_bits, 5, config->one_shot);  in max31865_init()
257 	data->config_control_bits |= config->fault_cycle & 0b00001100;  in max31865_init()
258 	WRITE_BIT(data->config_control_bits, 0, config->filter_50hz);  in max31865_init()
263 	max31865_set_three_wire(dev, config->three_wire);  in max31865_init()
271 		return -ENOTSUP;  in max31865_sample_fetch()
279 	struct max31865_data *data = dev->data;  in max31865_channel_get()
283 		return sensor_value_from_double(val, data->temperature);  in max31865_channel_get()
285 		return -ENOTSUP;  in max31865_channel_get()
294 		return -ENOTSUP;  in max31865_attr_set()
299 		return max31865_set_three_wire(dev, val->val1);  in max31865_attr_set()
301 		return -ENOTSUP;  in max31865_attr_set()