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_AMPLIFIER_H_
8 #define ZEPHYR_INCLUDE_DRIVERS_ADC_CURRENT_SENSE_AMPLIFIER_H_
9
10 #include <zephyr/drivers/adc.h>
11 #include <zephyr/drivers/gpio.h>
12
13 struct current_sense_amplifier_dt_spec {
14 const struct adc_dt_spec port;
15 uint32_t sense_micro_ohms;
16 uint32_t sense_gain_mult;
17 uint32_t sense_gain_div;
18 struct gpio_dt_spec power_gpio;
19 };
20
21 /**
22 * @brief Get current sensor information from devicetree.
23 *
24 * This returns a static initializer for a @p current_sense_amplifier_dt_spec structure
25 * given a devicetree node.
26 *
27 * @param node_id Devicetree node identifier.
28 *
29 * @return Static initializer for an current_sense_amplifier_dt_spec structure.
30 */
31 #define CURRENT_SENSE_AMPLIFIER_DT_SPEC_GET(node_id) \
32 { \
33 .port = ADC_DT_SPEC_GET(node_id), \
34 .sense_micro_ohms = DT_PROP(node_id, sense_resistor_micro_ohms), \
35 .sense_gain_mult = DT_PROP(node_id, sense_gain_mult), \
36 .sense_gain_div = DT_PROP(node_id, sense_gain_div), \
37 .power_gpio = GPIO_DT_SPEC_GET_OR(node_id, power_gpios, {0}), \
38 }
39
40 /**
41 * @brief Calculates the actual amperage from the measured voltage
42 *
43 * @param[in] spec current sensor specification from Devicetree.
44 * @param[in,out] v_to_i Pointer to the measured voltage in millivolts on input, and the
45 * corresponding scaled current value in milliamps on output.
46 */
47 static inline void
current_sense_amplifier_scale_dt(const struct current_sense_amplifier_dt_spec * spec,int32_t * v_to_i)48 current_sense_amplifier_scale_dt(const struct current_sense_amplifier_dt_spec *spec,
49 int32_t *v_to_i)
50 {
51 /* store in a temporary 64 bit variable to prevent overflow during calculation */
52 int64_t tmp = *v_to_i;
53
54 /* multiplies by 1,000,000 before dividing by sense resistance in micro-ohms. */
55 tmp = tmp * 1000000 / spec->sense_micro_ohms * spec->sense_gain_div / spec->sense_gain_mult;
56
57 *v_to_i = (int32_t)tmp;
58 }
59
60 #endif /* ZEPHYR_INCLUDE_DRIVERS_ADC_CURRENT_SENSE_AMPLIFIER_H_ */
61
