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The LED pulse width on the MAX30100 sensor determines how long the IR/Red LEDs are driven during each sample, directly affecting the emitted optical energy and hence the received signal amplitude. This parameter is highly dependent on the mechanical and optical integration of the sensor, such as: - The type and thickness of the optical window or lens covering the sensor. - The distance between the LED and photodiode. - The reflectivity of the target surface. For example: - A smartwatch or wearable ring with a thin glass window can operate with shorter pulses (200-400 us) to save power. - A medical-grade pulse oximeter or sensor mounted behind a thicker protective layer may require longer pulses (800-1600 us) for reliable signal amplitude. Because this configuration is determined by hardware design rather than by runtime conditions, it is appropriate to describe it in the DT. If not specified, the driver defaults to 1600 us to maintain existing behavior. Tested on: Raspberry Pi 3B + MAX30100 breakout board. Signed-off-by: Shrikant Raskar <raskar.shree97@gmail.com> Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
60 lines
1.4 KiB
YAML
60 lines
1.4 KiB
YAML
# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
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%YAML 1.2
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---
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$id: http://devicetree.org/schemas/iio/health/maxim,max30100.yaml#
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$schema: http://devicetree.org/meta-schemas/core.yaml#
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title: Maxim MAX30100 heart rate and pulse oximeter sensor
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maintainers:
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- Matt Ranostay <matt.ranostay@konsulko.com>
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properties:
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compatible:
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const: maxim,max30100
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reg:
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maxItems: 1
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interrupts:
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maxItems: 1
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description: Connected to ADC_RDY pin.
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maxim,led-current-microamp:
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minItems: 2
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maxItems: 2
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description: |
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LED current whilst the engine is running. First indexed value is
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the configuration for the RED LED, and second value is for the IR LED.
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maxim,pulse-width-us:
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description: |
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LED pulse width in microseconds. Appropriate pulse width depends on
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factors such as optical window absorption, LED-to-sensor distance,
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and expected reflectivity of the skin or contact surface.
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enum: [200, 400, 800, 1600]
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default: 1600
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additionalProperties: false
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required:
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- compatible
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- reg
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- interrupts
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examples:
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- |
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i2c {
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#address-cells = <1>;
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#size-cells = <0>;
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heart-rate@57 {
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compatible = "maxim,max30100";
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reg = <0x57>;
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maxim,led-current-microamp = <24000 50000>;
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interrupt-parent = <&gpio1>;
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interrupts = <16 2>;
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};
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};
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...
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