Line data    Source code

       1            0 : /*
       2              :  * Copyright (c) 2023 The ChromiumOS Authors
       3              :  *
       4              :  * SPDX-License-Identifier: Apache-2.0
       5              :  */
       6              : 
       7              : #ifndef ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_
       8              : #define ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_
       9              : 
      10              : #include <zephyr/drivers/adc.h>
      11              : 
      12            0 : struct voltage_divider_dt_spec {
      13            0 :         const struct adc_dt_spec port;
      14            0 :         uint32_t full_ohms;
      15            0 :         uint32_t output_ohms;
      16              : };
      17              : 
      18              : /**
      19              :  * @brief Get voltage divider information from devicetree.
      20              :  *
      21              :  * This returns a static initializer for a @p voltage_divider_dt_spec structure
      22              :  * given a devicetree node.
      23              :  *
      24              :  * @param node_id Devicetree node identifier.
      25              :  *
      26              :  * @return Static initializer for an voltage_divider_dt_spec structure.
      27              :  */
      28            1 : #define VOLTAGE_DIVIDER_DT_SPEC_GET(node_id)                                                       \
      29              :         {                                                                                          \
      30              :                 .port = ADC_DT_SPEC_GET(node_id),                                                  \
      31              :                 .full_ohms = DT_PROP_OR(node_id, full_ohms, 0),                                    \
      32              :                 .output_ohms = DT_PROP(node_id, output_ohms),                                      \
      33              :         }
      34              : 
      35              : /**
      36              :  * @brief Calculates the actual voltage from the measured voltage
      37              :  *
      38              :  * @param[in] spec voltage divider specification from Devicetree.
      39              :  * @param[in,out] v_to_v Pointer to the measured voltage on input, and the
      40              :  * corresponding scaled voltage value on output.
      41              :  *
      42              :  * @retval 0 on success
      43              :  * @retval -ENOTSUP if "full_ohms" is not specified
      44              :  */
      45            1 : static inline int voltage_divider_scale_dt(const struct voltage_divider_dt_spec *spec,
      46              :                                            int32_t *v_to_v)
      47              : {
      48              :         /* cannot be scaled if "full_ohms" is not specified */
      49              :         if (spec->full_ohms == 0) {
      50              :                 return -ENOTSUP;
      51              :         }
      52              : 
      53              :         /* voltage scaled by voltage divider values using DT binding */
      54              :         *v_to_v = (int64_t)*v_to_v * spec->full_ohms / spec->output_ohms;
      55              : 
      56              :         return 0;
      57              : }
      58              : 
      59              : #endif /* ZEPHYR_INCLUDE_DRIVERS_ADC_VOLTAGE_DIVIDER_H_ */