saul: initial import of saul_bat_voltage module

drivers/Makefile.dep

@@ -264,6 +264,11 @@ ifneq (,$(filter ws281x_%,$(USEMODULE)))
   USEMODULE += ws281x
 endif
 
+ifneq (,$(filter saul_bat_voltage,$(USEMODULE)))
+  FEATURES_REQUIRED += periph_adc
+  FEATURES_REQUIRED += board_bat_voltage
+endif
+
 ifneq (,$(filter saul_adc,$(USEMODULE)))
   FEATURES_REQUIRED += periph_adc
 endif

drivers/include/saul/bat_voltage.h

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_saul
+ * @{
+ *
+ * @file
+ * @brief       Parameter definitions for mapping battery voltage to SAUL
+ *
+ * @author      Martine S. Lenders <martine.lenders@tu-dresden.de>
+ */
+
+#ifndef SAUL_BAT_VOLTAGE_H
+#define SAUL_BAT_VOLTAGE_H
+
+#include <stdint.h>
+
+#include "periph/adc.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * @brief SAUL battery voltage configuration values
+ */
+typedef struct {
+    const char *name;       /**< name of the device connected to this pin */
+    int8_t phydat_scale;    /**< Phydat scale of the resulting voltage */
+    adc_t line;             /**< ADC line to initialize and expose */
+    adc_res_t res;          /**< ADC resolution */
+    /**
+     * @brief   Conversion function to convert raw ADC data to voltage
+     *
+     * @param[in] adc_sample    The raw ADC sample.
+     *
+     * @return Voltage value for phydat.
+     */
+    int16_t (*convert)(int32_t adc_sample);
+} saul_bat_voltage_params_t;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* SAUL_BAT_VOLTAGE_H */
+/** @} */

drivers/saul/Makefile

@@ -3,6 +3,9 @@ SRC = saul.c saul_str.c
 ifneq (,$(filter saul_gpio,$(USEMODULE)))
   SRC += gpio_saul.c
 endif
+ifneq (,$(filter saul_bat_voltage,$(USEMODULE)))
+  SRC += bat_voltage_saul.c
+endif
 ifneq (,$(filter saul_adc,$(USEMODULE)))
   SRC += adc_saul.c
 endif

drivers/saul/bat_voltage_saul.c

@@ -0,0 +1,45 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @ingroup     drivers_saul
+ * @{
+ *
+ * @file
+ * @brief       SAUL wrapper to gauge battery voltage.
+ *
+ * Adafruit Feather-type boards typically have an ADC pin exposed to read
+ * the battery voltage.
+ *
+ * @author      Martine S. Lenders <martine.lenders@tu-dresden.de>
+ *
+ * @}
+ */
+
+#include <string.h>
+
+#include "saul.h"
+#include "saul/bat_voltage.h"
+#include "phydat.h"
+#include "periph/adc.h"
+
+static int read_adc(const void *dev, phydat_t *res)
+{
+    const saul_bat_voltage_params_t *params = *((const saul_bat_voltage_params_t **)dev);
+    int32_t sample = adc_sample(params->line, params->res);
+    res->val[0] = params->convert(sample);
+    res->unit = UNIT_V;
+    res->scale = params->phydat_scale;
+    return 1;
+}
+
+const saul_driver_t bat_voltage_saul_driver = {
+    .read = read_adc,
+    .write = saul_write_notsup,
+    .type = SAUL_SENSE_VOLTAGE,
+};

drivers/saul/init_devs/auto_init_saul_bat_voltage.c

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2024 TU Dresden
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ *
+ */
+
+/**
+ * @ingroup     sys_auto_init_saul
+ * @{
+ *
+ * @file
+ * @brief       Auto initialization of mapping battery voltage to SAUL
+ *
+ * @author      Martine S. Lenders <martine.lenders@tu-dresden.de>
+ *
+ * @}
+ */
+
+#include "log.h"
+#include "saul_reg.h"
+#include "saul/bat_voltage.h"
+#include "bat_voltage_params.h"
+
+/**
+ * @brief   Define the number of configured sensors
+ */
+#define SAUL_BAT_VOLTAGE_NUMOF  ARRAY_SIZE(saul_bat_voltage_params)
+
+/**
+ * @brief   Allocate memory for pointers to the BAT voltage parameter structs
+ *
+ * We use this extra level of indirection to be able to keep the saul_bat_voltage_params
+ * array const and residing in ROM.
+ */
+static const saul_bat_voltage_params_t *saul_bat_voltages[SAUL_BAT_VOLTAGE_NUMOF];
+
+/**
+ * @brief   Memory for the registry entries
+ */
+static saul_reg_t saul_reg_entries[SAUL_BAT_VOLTAGE_NUMOF];
+
+/**
+ * @brief   Reference the driver struct
+ */
+extern saul_driver_t bat_voltage_saul_driver;
+
+void auto_init_saul_bat_voltage(void)
+{
+    for (unsigned i = 0; i < SAUL_BAT_VOLTAGE_NUMOF; i++) {
+        const saul_bat_voltage_params_t *p = &saul_bat_voltage_params[i];
+        saul_bat_voltages[i] = p;
+
+        printf("[auto_init_saul] initializing BAT voltage #%u\n", i);
+
+        saul_reg_entries[i].dev = &saul_bat_voltages[i];
+        saul_reg_entries[i].name = p->name;
+        saul_reg_entries[i].driver = &bat_voltage_saul_driver;
+        /* initialize the ADC line */
+        adc_init(p->line);
+        /* add to registry */
+        saul_reg_add(&(saul_reg_entries[i]));
+    }
+}

drivers/saul/init_devs/init.c

@@ -31,6 +31,10 @@ void saul_init_devs(void)
         extern void auto_init_saul_adc(void);
         auto_init_saul_adc();
     }
+    if (IS_USED(MODULE_SAUL_BAT_VOLTAGE)) {
+        extern void auto_init_saul_bat_voltage(void);
+        auto_init_saul_bat_voltage();
+    }
     if (IS_USED(MODULE_SAUL_GPIO)) {
         extern void auto_init_gpio(void);
         auto_init_gpio();

features.yaml

@@ -796,6 +796,8 @@ groups:
   - title: Platform Specific
     help: Things specific to a single MCU family / MCU vendor
     features:
+    - name: board_bat_voltage
+      help: Measures battery voltage based on ADC sampling.
     - name: periph_ics
       help: An NXP Kinetis Internal Clock Source Controller (ICS peripheral) is
             present.

makefiles/features_existing.inc.mk

@@ -42,6 +42,7 @@ FEATURES_EXISTING := \
     ble_nimble_netif \
     ble_phy_2mbit \
     ble_phy_coded \
+    board_bat_voltage \
     bootloader_stm32 \
     can_rx_mailbox \
     cortexm_fpu \

makefiles/pseudomodules.inc.mk

@@ -374,6 +374,7 @@ PSEUDOMODULES += fortuna_reseed
 PSEUDOMODULES += riotboot_%
 PSEUDOMODULES += rtt_cmd
 PSEUDOMODULES += saul_adc
+PSEUDOMODULES += saul_bat_voltage
 PSEUDOMODULES += saul_default
 PSEUDOMODULES += saul_gpio
 PSEUDOMODULES += saul_nrf_temperature