feat(drivers): add driver for MAX17048 fuel gauge

app/drivers/sensor/CMakeLists.txt

@@ -2,4 +2,5 @@
 # SPDX-License-Identifier: MIT
 
 add_subdirectory_ifdef(CONFIG_ZMK_BATTERY battery)
-add_subdirectory_ifdef(CONFIG_EC11 ec11)
+add_subdirectory_ifdef(CONFIG_EC11 ec11)
+add_subdirectory_ifdef(CONFIG_MAX17048 max17048)

app/drivers/sensor/Kconfig

@@ -2,4 +2,5 @@
 # SPDX-License-Identifier: MIT
 
 rsource "battery/Kconfig"
-rsource "ec11/Kconfig"
+rsource "ec11/Kconfig"
+rsource "max17048/Kconfig"

app/drivers/sensor/max17048/CMakeLists.txt

@@ -0,0 +1,9 @@
+# Copyright (c) 2022 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+zephyr_include_directories(.)
+
+zephyr_library()
+
+zephyr_library_sources_ifdef(CONFIG_MAX17048  max17048.c)
+zephyr_library_sources_ifndef(CONFIG_MAX17048 ${ZEPHYR_BASE}/misc/empty_file.c)

app/drivers/sensor/max17048/Kconfig

@@ -0,0 +1,9 @@
+# Copyright (c) 2022 The ZMK Contributors
+# SPDX-License-Identifier: MIT
+
+config MAX17048
+	bool "MAX17048 Fuel Gauge"
+	depends on I2C
+	help
+	  Enable I2C-based driver for MAX17048/9 Fuel Gauge. Supports measuring
+	  battery voltage and state-of-charge.

app/drivers/sensor/max17048/max17048.c

@@ -0,0 +1,196 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#define DT_DRV_COMPAT maxim_max17048
+
+#include <device.h>
+#include <kernel.h>
+#include <sys/util.h>
+#include <logging/log.h>
+#include <drivers/i2c.h>
+#include <sys/byteorder.h>
+#include <drivers/sensor.h>
+
+#include "max17048.h"
+
+LOG_MODULE_REGISTER(MAX17048, CONFIG_SENSOR_LOG_LEVEL);
+
+static int read_register(const struct device *dev, uint8_t reg, uint16_t *value) {
+
+    if (k_is_in_isr()) {
+        return -EWOULDBLOCK;
+    }
+
+    struct max17048_drv_data *const drv_data = dev->data;
+    uint16_t dev_addr = ((struct max17048_config *)dev->config)->device_addr;
+
+    uint16_t data = 0;
+    int ret = i2c_burst_read(drv_data->i2c, dev_addr, reg, (uint8_t *)&data, sizeof(data));
+    if (ret != 0) {
+        LOG_DBG("i2c_write_read FAIL %d\n", ret);
+        return ret;
+    }
+
+    *value = sys_le16_to_cpu(data);
+    return 0;
+}
+
+static int write_register(const struct device *dev, uint8_t reg, uint16_t value) {
+
+    if (k_is_in_isr()) {
+        return -EWOULDBLOCK;
+    }
+
+    struct max17048_drv_data *const drv_data = dev->data;
+
+    uint16_t data = sys_cpu_to_le16(value);
+    uint16_t dev_addr = ((struct max17048_config *)dev->config)->device_addr;
+
+    return i2c_burst_write(drv_data->i2c, dev_addr, reg, (uint8_t *)&data, sizeof(data));
+}
+
+static int set_rcomp_value(const struct device *dev, uint8_t rcomp_value) {
+
+    uint16_t tmp = 0;
+    int err = read_register(dev, REG_CONFIG, &tmp);
+    if (err != 0) {
+        return err;
+    }
+
+    tmp = ((uint16_t)rcomp_value << 8) | (tmp & 0xFF);
+    err = write_register(dev, REG_CONFIG, tmp);
+    if (err != 0) {
+        return err;
+    }
+
+    LOG_DBG("set RCOMP to %d", rcomp_value);
+    return 0;
+}
+
+static int set_sleep_enabled(const struct device *dev, bool sleep) {
+    uint16_t tmp = 0;
+    int err = read_register(dev, REG_CONFIG, &tmp);
+    if (err != 0) {
+        return err;
+    }
+
+    if (sleep) {
+        tmp |= 0x80;
+    } else {
+        tmp &= ~0x0080;
+    }
+
+    err = write_register(dev, REG_CONFIG, tmp);
+    if (err != 0) {
+        return err;
+    }
+
+    LOG_DBG("sleep mode %s", sleep ? "enabled" : "disabled");
+    return 0;
+}
+
+static int max17048_sample_fetch(const struct device *dev, enum sensor_channel chan) {
+    struct max17048_drv_data *const data = dev->data;
+
+    if (chan != SENSOR_CHAN_GAUGE_VOLTAGE && chan != SENSOR_CHAN_GAUGE_STATE_OF_CHARGE) {
+        LOG_DBG("unsupported channel %d", chan);
+        return -ENOTSUP;
+    }
+
+    int err = read_register(dev, REG_STATE_OF_CHARGE, &data->raw_state_of_charge);
+    if (err != 0) {
+        LOG_WRN("failed to read state-of-charge: %d", err);
+        return err;
+    }
+
+    err = read_register(dev, REG_VCELL, &data->raw_vcell);
+    if (err != 0) {
+        LOG_WRN("failed to read vcell: %d", err);
+        return err;
+    }
+
+    LOG_DBG("read values: soc=%d, vcell=%d", data->raw_state_of_charge, data->raw_vcell);
+
+    return 0;
+}
+
+static int max17048_channel_get(const struct device *dev, enum sensor_channel chan,
+                                struct sensor_value *val) {
+
+    struct max17048_drv_data *const data = dev->data;
+    unsigned int tmp = 0;
+
+    switch (chan) {
+    case SENSOR_CHAN_GAUGE_VOLTAGE:
+        // 1250 / 16 = 78.125
+        tmp = data->raw_vcell * 1250 / 16;
+        val->val1 = tmp / 1000000;
+        val->val2 = tmp % 1000000;
+        break;
+
+    case SENSOR_CHAN_GAUGE_STATE_OF_CHARGE:
+        val->val1 = (data->raw_state_of_charge >> 8);
+        val->val2 = (data->raw_state_of_charge & 0xFF) * 1000000 / 256;
+        break;
+
+    default:
+        return -ENOTSUP;
+    }
+
+    return 0;
+}
+
+static int max17048_init(const struct device *dev) {
+    struct max17048_drv_data *driver_data = dev->data;
+    const struct max17048_config *driver_config = dev->config;
+
+    driver_data->i2c = device_get_binding((char *)driver_config->i2c_device_name);
+    if (!driver_data->i2c) {
+        LOG_DBG("Unable to get i2c device");
+        return -ENODEV;
+    }
+
+    if (!device_is_ready(driver_data->i2c)) {
+        LOG_WRN("i2c bus not ready!");
+        return -EINVAL;
+    }
+
+    uint16_t ic_version = 0;
+    int err = read_register(dev, REG_VERSION, &ic_version);
+    if (err != 0) {
+        LOG_WRN("could not get IC version!");
+        return err;
+    }
+
+    // bring the device out of sleep
+    set_sleep_enabled(dev, false);
+
+    // set the default rcomp value -- 0x97, as stated in the datasheet
+    set_rcomp_value(dev, 0x97);
+
+    LOG_INF("device initialised at 0x%x (i2c=%s) (version %d)", driver_config->device_addr,
+            driver_config->i2c_device_name, ic_version);
+
+    return 0;
+}
+
+static const struct sensor_driver_api max17048_api_table = {.sample_fetch = max17048_sample_fetch,
+                                                            .channel_get = max17048_channel_get};
+
+#define MAX17048_INIT(inst)                                                                        \
+    static struct max17048_config max17048_##inst##_config = {                                     \
+        .i2c_device_name = DT_INST_BUS_LABEL(inst),                                                \
+        .device_addr = DT_INST_REG_ADDR(inst),                                                     \
+    };                                                                                             \
+                                                                                                   \
+    static struct max17048_drv_data max17048_##inst##_drvdata = {};                                \
+                                                                                                   \
+    /* This has to init after SPI master */                                                        \
+    DEVICE_DT_INST_DEFINE(inst, max17048_init, NULL, &max17048_##inst##_drvdata,                   \
+                          &max17048_##inst##_config, POST_KERNEL, CONFIG_SENSOR_INIT_PRIORITY,     \
+                          &max17048_api_table);
+
+DT_INST_FOREACH_STATUS_OKAY(MAX17048_INIT)

app/drivers/sensor/max17048/max17048.h

@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2022 The ZMK Contributors
+ *
+ * SPDX-License-Identifier: MIT
+ */
+
+#pragma once
+
+#include <device.h>
+#include <sys/util.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define REG_VCELL 0x02
+#define REG_STATE_OF_CHARGE 0x04
+#define REG_MODE 0x06
+#define REG_VERSION 0x08
+#define REG_HIBERNATE 0x0A
+#define REG_CONFIG 0x0C
+#define REG_VALERT 0x14
+#define REG_CHARGE_RATE 0x16
+#define REG_VRESET 0x18
+#define REG_STATUS 0x1A
+
+struct max17048_config {
+    const char *i2c_device_name;
+    uint16_t device_addr;
+};
+
+struct max17048_drv_data {
+    const struct device *i2c;
+
+    uint16_t raw_state_of_charge;
+    uint16_t raw_charge_rate;
+    uint16_t raw_vcell;
+};
+
+#ifdef __cplusplus
+}
+#endif