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Jeppe Odgaard
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drivers: led: add led_dac
Add LED driver support for DAC based LED drivers. Signed-off-by: Jeppe Odgaard <[email protected]>
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‎drivers/led/CMakeLists.txt

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@@ -6,6 +6,7 @@ zephyr_library()
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zephyr_library_sources_ifdef(CONFIG_HT16K33 ht16k33.c)
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zephyr_library_sources_ifdef(CONFIG_IS31FL3216A is31fl3216a.c)
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zephyr_library_sources_ifdef(CONFIG_LED_DAC led_dac.c)
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zephyr_library_sources_ifdef(CONFIG_LED_GPIO led_gpio.c)
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zephyr_library_sources_ifdef(CONFIG_LED_NPM1300 led_npm1300.c)
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zephyr_library_sources_ifdef(CONFIG_LED_PWM led_pwm.c)

‎drivers/led/Kconfig

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@@ -26,6 +26,7 @@ config LED_SHELL
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help
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Enable LED shell for testing.
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source "drivers/led/Kconfig.dac"
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source "drivers/led/Kconfig.gpio"
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source "drivers/led/Kconfig.ht16k33"
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source "drivers/led/Kconfig.is31fl3216a"

‎drivers/led/Kconfig.dac

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# Copyright (c) 2025 Prevas A/S
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# SPDX-License-Identifier: Apache-2.0
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config LED_DAC
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bool "DAC LED driver"
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default y
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depends on DT_HAS_DAC_LEDS_ENABLED
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select DAC
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help
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Enable DAC LED driver.
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The driver is normally used with a VCCS (Voltage Controlled Current
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Source) between the DAC and the LED.
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It might be possible to use this driver to supply an LED directly
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from a DAC, but LED_PWM is most likely more suited for this purpose.
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If the DAC is used without a VCCS, its capabilities should be checked
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carefully, and the output buffer should be enabled.

‎drivers/led/led_dac.c

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/*
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* Copyright (c) 2025 Prevas A/S
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* SPDX-License-Identifier: Apache-2.0
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*/
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#define DT_DRV_COMPAT dac_leds
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#include <errno.h>
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#include <stdint.h>
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#include <zephyr/device.h>
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#include <zephyr/drivers/dac.h>
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#include <zephyr/drivers/led.h>
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#include <zephyr/sys/math_extras.h>
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struct led_dac_leds {
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const struct device *dac;
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struct dac_channel_cfg chan_cfg;
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uint32_t dac_max;
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uint32_t dac_min;
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};
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struct led_dac_config {
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const struct led_dac_leds *leds;
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uint8_t num_leds;
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};
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static int led_dac_set_raw(const struct device *dev, uint32_t led, uint32_t value)
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{
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const struct led_dac_config *config = dev->config;
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return dac_write_value(config->leds[led].dac, config->leds[led].chan_cfg.channel_id, value);
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}
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static int led_dac_set_brightness(const struct device *dev, uint32_t led, uint8_t pct)
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{
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const struct led_dac_config *config = dev->config;
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uint32_t value;
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if (led >= config->num_leds) {
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return -EINVAL;
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}
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value = pct > 0 ? config->leds[led].dac_min + (uint64_t)(config->leds[led].dac_max -
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config->leds[led].dac_min) *
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pct / 100
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: 0;
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return led_dac_set_raw(dev, led, value);
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}
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static inline int led_dac_on(const struct device *dev, uint32_t led)
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{
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const struct led_dac_config *config = dev->config;
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if (led >= config->num_leds) {
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return -EINVAL;
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}
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return led_dac_set_raw(dev, led, config->leds[led].dac_max);
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}
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static inline int led_dac_off(const struct device *dev, uint32_t led)
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{
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const struct led_dac_config *config = dev->config;
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if (led >= config->num_leds) {
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return -EINVAL;
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}
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return led_dac_set_raw(dev, led, 0);
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}
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static DEVICE_API(led, led_dac_api) = {
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.on = led_dac_on,
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.off = led_dac_off,
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.set_brightness = led_dac_set_brightness,
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};
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static int led_dac_init(const struct device *dev)
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{
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const struct led_dac_config *config = dev->config;
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int ret;
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for (uint8_t i = 0; i < config->num_leds; ++i) {
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const struct led_dac_leds *led = &config->leds[i];
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if (!device_is_ready(led->dac)) {
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return -ENODEV;
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}
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ret = dac_channel_setup(led->dac, &led->chan_cfg);
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if (ret != 0) {
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return ret;
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}
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}
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return 0;
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}
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#define LED_DAC_MAX_MV(n) DT_PROP(n, voltage_max_dac_mv)
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#define LED_DAC_MAX_VAL(n) (BIT(DT_PROP(n, resolution)) - 1)
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#define LED_DAC_MAX_BRIGHTNESS(n) \
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COND_CODE_1(DT_NODE_HAS_PROP(n, voltage_max_brightness_mv), \
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(DT_PROP(n, voltage_max_brightness_mv) * LED_DAC_MAX_VAL(n) / LED_DAC_MAX_MV(n)), \
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(LED_DAC_MAX_VAL(n)))
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#define LED_DAC_MIN_BRIGHTNESS(n) \
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COND_CODE_1(DT_NODE_HAS_PROP(n, voltage_min_brightness_mv), \
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(DT_PROP(n, voltage_min_brightness_mv) * LED_DAC_MAX_VAL(n) / LED_DAC_MAX_MV(n)), \
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(0))
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#define LED_DAC_DT_GET(n) \
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{ \
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.dac = DEVICE_DT_GET(DT_PHANDLE(n, dac_dev)), \
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.chan_cfg = {.channel_id = DT_PROP(n, channel), \
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.resolution = DT_PROP(n, resolution), \
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.buffered = DT_PROP(n, output_buffer), \
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.internal = false}, \
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.dac_max = LED_DAC_MAX_BRIGHTNESS(n), .dac_min = LED_DAC_MIN_BRIGHTNESS(n) \
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}
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#define LED_DAC_DEFINE(n) \
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BUILD_ASSERT((DT_NODE_HAS_PROP(n, voltage_max_brightness_mv) || \
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DT_NODE_HAS_PROP(n, voltage_min_brightness_mv)) == \
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DT_NODE_HAS_PROP(n, voltage_max_dac_mv), \
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"'voltage-max-dac-mv' must be set when 'voltage-max-brightness-mv' or " \
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"'voltage-max-brightness-mv' is set"); \
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\
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static const struct led_dac_leds led_dac_##n[] = { \
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DT_INST_FOREACH_CHILD_SEP(n, LED_DAC_DT_GET, (,))}; \
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\
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static const struct led_dac_config led_config_##n = { \
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.leds = led_dac_##n, \
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.num_leds = ARRAY_SIZE(led_dac_##n), \
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}; \
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\
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DEVICE_DT_INST_DEFINE(n, &led_dac_init, NULL, NULL, &led_config_##n, POST_KERNEL, \
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CONFIG_LED_INIT_PRIORITY, &led_dac_api);
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DT_INST_FOREACH_STATUS_OKAY(LED_DAC_DEFINE)

‎dts/bindings/led/dac-leds.yaml

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# Copyright (c) 2018, Linaro Limited
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# Copyright (c) 2025, Prevas A/S
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# SPDX-License-Identifier: Apache-2.0
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title: Group of DAC-controlled LEDs.
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description: |
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Each LED is defined in a child node of the dac-leds node.
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Here is an example which defines an LED in the node /leds:
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/ {
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leds {
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compatible = "dac-leds";
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led_0 {
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dac-dev = <&dac1>;
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channel = <0>;
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resolution = <12>;
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};
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led_1 {
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dac-dev = <&dac1>;
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channel = <1>;
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resolution = <12>;
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voltage-min-brightness-mv = <1400>;
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voltage-max-brightness-mv = <2700>;
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voltage-max-dac-mv = <3300>;
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output-buffer;
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};
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};
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};
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Above:
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- led_0 uses dac1 channel 0 with 12 bit resolution.
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- led_1 uses dac1 channel 1 with 12 bit resolution.
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compatible: "dac-leds"
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child-binding:
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description: DAC LED child node
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properties:
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dac-dev:
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type: phandle
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required: true
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description: |
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Property containing phandle to DAC e.g. &dac.
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channel:
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type: int
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required: true
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description: |
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The DAC channel.
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resolution:
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type: int
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required: true
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description: |
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The DAC resolution to use.
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voltage-min-brightness-mv:
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type: int
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description: |
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Voltage at brightness 0%.
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If not specified the minimum DAC output voltage is used.
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voltage-max-brightness-mv:
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type: int
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description: |
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Voltage at brightness 100%.
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If not specified the maximum DAC output voltage is used.
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voltage-max-dac-mv:
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type: int
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description: |
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The DAC maximum output voltage.
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Required if voltage-min-brightness-mv or voltage-max-brightness-mv is set.
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output-buffer:
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type: boolean
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description: |
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Enable the output buffer of the DAC.
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This is required if it is used to drive an LED directly.

‎tests/drivers/build_all/led/app.overlay

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@@ -15,6 +15,26 @@
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#address-cells = <1>;
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#size-cells = <1>;
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test_dac: dac@dac0dac0 {
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compatible = "vnd,dac";
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reg = <0xdac0dac0 0x1000>;
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status = "okay";
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#io-channel-cells = <1>;
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};
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test_dac_leds {
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compatible = "dac-leds";
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test_dac_led0: test_dac_led_0 {
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dac-dev = <&test_dac>;
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channel = <0>;
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resolution = <16>;
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voltage-min-brightness-mv = <123>;
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voltage-max-brightness-mv = <1234>;
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voltage-max-dac-mv = <3456>;
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output-buffer;
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};
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};
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test_gpio: gpio@deadbeef {
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compatible = "vnd,gpio";
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gpio-controller;

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