1 /*
2  * Copyright (c) 2023 The ChromiumOS Authors
3  *
4  * SPDX-License-Identifier: Apache-2.0
5  */
6 
7 #ifndef ZEPHYR_INCLUDE_DRIVERS_ADC_CURRENT_SENSE_SHUNT_H_
8 #define ZEPHYR_INCLUDE_DRIVERS_ADC_CURRENT_SENSE_SHUNT_H_
9 
10 #include <zephyr/drivers/adc.h>
11 
12 struct current_sense_shunt_dt_spec {
13 	const struct adc_dt_spec port;
14 	uint32_t shunt_micro_ohms;
15 };
16 
17 /**
18  * @brief Get current sensor information from devicetree.
19  *
20  * This returns a static initializer for a @p current_sense_shunt_dt_spec structure
21  * given a devicetree node.
22  *
23  * @param node_id Devicetree node identifier.
24  *
25  * @return Static initializer for an current_sense_shunt_dt_spec structure.
26  */
27 #define CURRENT_SENSE_SHUNT_DT_SPEC_GET(node_id)                                                   \
28 	{                                                                                          \
29 		.port = ADC_DT_SPEC_GET(node_id),                                                  \
30 		.shunt_micro_ohms = DT_PROP(node_id, shunt_resistor_micro_ohms),                   \
31 	}
32 
33 /**
34  * @brief Calculates the actual amperage from the measured voltage
35  *
36  * @param[in] spec current sensor specification from Devicetree.
37  * @param[in,out] v_to_i Pointer to the measured voltage in millivolts on input, and the
38  * corresponding scaled current value in milliamps on output.
39  */
current_sense_shunt_scale_dt(const struct current_sense_shunt_dt_spec * spec,int32_t * v_to_i)40 static inline void current_sense_shunt_scale_dt(const struct current_sense_shunt_dt_spec *spec,
41 					  int32_t *v_to_i)
42 {
43 	/* store in a temporary 64 bit variable to prevent overflow during calculation */
44 	int64_t tmp = *v_to_i;
45 
46 	/* multiplies by 1,000,000 before dividing by shunt resistance in micro-ohms. */
47 	tmp = tmp * 1000000 / spec->shunt_micro_ohms;
48 
49 	*v_to_i = (int32_t)tmp;
50 }
51 
52 #endif /* ZEPHYR_INCLUDE_DRIVERS_ADC_CURRENT_SENSE_SHUNT_H_ */
53