Max22007 dev #3015
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| What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_ldac_update | ||
| KernelVersion: 6.13 | ||
| Contact: [email protected] | ||
| Description: | ||
| Trigger LDAC (Load DAC) update for the specified channel. Write 1 to update DAC outputs. | ||
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| What: /sys/bus/iio/devices/iio:deviceX/out_currentY_ldac_update | ||
| KernelVersion: 6.13 | ||
| Contact: [email protected] | ||
| Description: | ||
| Trigger LDAC (Load DAC) update for the specified channel. | ||
| Writing 1 will transfer the DAC register value to the actual | ||
| DAC output, effectively updating the analog output current. | ||
| Writing 0 has no effect. This is useful when using the | ||
| transparent latch mode is disabled, allowing manual control | ||
| over when DAC register changes take effect on the output. | ||
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| What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_powermode | ||
| What: /sys/bus/iio/devices/iio:deviceX/out_currentY_powermode | ||
| KernelVersion: 6.13 | ||
| Contact: [email protected] | ||
| Description: | ||
| Control the power state of the specified channel. Write "on" to | ||
| enable the channel output, or "off" to disable it. Reading | ||
| returns the current power state. | ||
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Contributor
There was a problem hiding this comment. Why can't this be supported with
Collaborator
There was a problem hiding this comment. Agreed. With the above, I guess we do not need any custom ABI |
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| What: /sys/bus/iio/devices/iio:deviceX/out_voltageY_powermode_available | ||
| What: /sys/bus/iio/devices/iio:deviceX/out_currentY_powermode_available | ||
| KernelVersion: 6.13 | ||
| Contact: [email protected] | ||
| Description: | ||
| Shows the available power modes for the channel. Always returns | ||
| "on off". | ||
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| # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause) | ||
| %YAML 1.2 | ||
| --- | ||
| $id: http://devicetree.org/schemas/iio/dac/adi,max22007.yaml# | ||
| $schema: http://devicetree.org/meta-schemas/core.yaml# | ||
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| title: Analog Devices MAX22007 DAC device driver | ||
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| maintainers: | ||
| - Janani Sunil <[email protected]> | ||
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| description: | ||
| The MAX22007 is a quad-channel, 12-bit digital-to-analog converter (DAC) | ||
| with integrated precision output amplifiers and current output capability. | ||
| Each channel can be independently configured for voltage or current output. | ||
| The driver supports runtime LDAC (Latch DAC) control via per-channel sysfs | ||
| attributes for precise output timing control. | ||
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Contributor
There was a problem hiding this comment. sysfs is a Linux thing. Device tree is supposed to be project agnostic. Drop these last two lines. |
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| Datasheet available at https://www.analog.com/en/products/max22007.html | ||
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| properties: | ||
| compatible: | ||
| const: adi,max22007 | ||
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| reg: | ||
| maxItems: 1 | ||
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| spi-max-frequency: | ||
| maximum: 500000 | ||
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| '#address-cells': | ||
| const: 1 | ||
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| '#size-cells': | ||
| const: 0 | ||
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| vdd-supply: | ||
| description: Low-Voltage Power Supply from +2.7V to +5.5V. | ||
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| hvdd-supply: | ||
| description: | ||
| Positive High-Voltage Power Supply from +8V to (HVSS +24V) for | ||
| the Output Channels. | ||
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| hvss-supply: | ||
| description: | ||
| Negative High-Voltage Power Supply from -2V to 0V for the Output Channels. | ||
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| adi,crc-disable: | ||
| type: boolean | ||
| description: | ||
| Disable CRC8 error checking for SPI communications. By default, CRC8 is | ||
| enabled for data integrity verification. Set this property to disable it. | ||
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Contributor
There was a problem hiding this comment. I see in the data sheet that SPI transfers can run with CRC disabled (set CRC_EN field to 0x0 within the configuration register (0x03) ). For max22007, CRC is a runtime configuration and has nothing to do with how hardware is set up. Drop this property. |
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| reset-gpios: | ||
| maxItems: 1 | ||
| description: | ||
| GPIO used for hardware reset of the device. If not specified, the driver | ||
| will use software reset via SPI register. | ||
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Collaborator
There was a problem hiding this comment. As mentioned by @machschmitt, don't mention things "the driver will....". Bindings is about HW description and we should not talk about any implementation specifics. Hence, I would drop the description in here. |
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| patternProperties: | ||
| "^channel@[0-3]$": | ||
| type: object | ||
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Contributor
There was a problem hiding this comment. we have bindings for common DAC properties (Documentation/devicetree/bindings/iio/dac/dac.yaml). I think you won't need required:
- regat least.
Collaborator
There was a problem hiding this comment. But I would argue that if reg is the only thing we take from it, kind of not sure if we should take it. |
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| description: | ||
| Represents the external channels which are connected to the DAC. | ||
| Channels not specified in the device tree will be powered off. | ||
| properties: | ||
| reg: | ||
| description: | ||
| This represents the channel number. | ||
| maximum: 3 | ||
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| adi,dac-latch-mode: | ||
| description: | ||
| DAC latch control mode for the channel. | ||
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Collaborator
There was a problem hiding this comment. Here the description does not add much when compared to the property name. If you're used to these chips, you know what this is about but if you are not... Please add brief description of what is this about (and remember, just in terms of HW) |
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| $ref: /schemas/types.yaml#/definitions/string | ||
| enum: [ldac-control, transparent] | ||
| default: ldac-control | ||
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| adi,mode: | ||
| description: | ||
| Output mode for the channel. | ||
| $ref: /schemas/types.yaml#/definitions/string | ||
| enum: [voltage, current] | ||
| default: voltage | ||
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Contributor
There was a problem hiding this comment. I wonder if it could use |
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| required: | ||
| - reg | ||
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| additionalProperties: false | ||
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| required: | ||
| - compatible | ||
| - reg | ||
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| anyOf: | ||
| - required: [channel@0] | ||
| - required: [channel@1] | ||
| - required: [channel@2] | ||
| - required: [channel@3] | ||
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Collaborator
There was a problem hiding this comment. At least vdd should be also required. If the other regulators are not optional, they should be also required |
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| allOf: | ||
| - $ref: /schemas/spi/spi-peripheral-props.yaml# | ||
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There was a problem hiding this comment. nitpicking: this can be simplified. |
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| unevaluatedProperties: false | ||
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| examples: | ||
| - | | ||
| #include <dt-bindings/gpio/gpio.h> | ||
| spi { | ||
| #address-cells = <1>; | ||
| #size-cells = <0>; | ||
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| dac@0 { | ||
| compatible = "adi,max22007"; | ||
| reg = <0>; | ||
| spi-max-frequency = <500000>; | ||
| reset-gpios = <&gpio 19 GPIO_ACTIVE_LOW>; | ||
| #address-cells = <1>; | ||
| #size-cells = <0>; | ||
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| channel@0 { | ||
| reg = <0>; | ||
| adi,mode = "voltage"; | ||
| adi,dac-latch-mode = "ldac-control"; | ||
| }; | ||
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| channel@1 { | ||
| reg = <1>; | ||
| adi,mode = "current"; | ||
| adi,dac-latch-mode = "transparent"; | ||
| }; | ||
| }; | ||
| }; | ||
| ... | ||
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@@ -31,3 +31,4 @@ Industrial I/O Kernel Drivers | |
| adxl380 | ||
| bno055 | ||
| ep93xx_adc | ||
| max22007 | ||
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| .. SPDX-License-Identifier: GPL-2.0-only | ||
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| =============== | ||
| MAX22007 driver | ||
| =============== | ||
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| Device driver for Analog Devices Inc. MAX22007 quad-channel industrial DAC. | ||
| The module name is ``max22007``. | ||
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| Supported devices | ||
| ================= | ||
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| * `MAX22007 <https://www.analog.com/en/products/max22007.html>`_ | ||
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| Wiring connections | ||
| ================== | ||
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| The MAX22007 uses a standard SPI interface. | ||
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| Device Tree Configuration | ||
| ========================= | ||
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| The device supports both global and per-channel configuration through device tree. | ||
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| Global Properties: | ||
| * ``adi,crc-disable``: Disable CRC8 error checking for SPI communications (optional, CRC enabled by default) | ||
| * ``reset-gpios``: GPIO pin for hardware reset (optional, falls back to software reset if not specified) | ||
| * ``vdd-supply``: Low-Voltage Power Supply from +2.7V to +5.5V (optional) | ||
| * ``hvdd-supply``: Positive High-Voltage Power Supply from +8V to (HVSS +24V) for the Output Channels (optional) | ||
| * ``hvss-supply``: Negative High-Voltage Power Supply from -2V to 0V for the Output Channels (optional) | ||
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| Per-channel properties: | ||
| * ``adi,dac-latch-mode``: Controls when DAC updates occur | ||
| - "ldac-control": LDAC pin controls the latch (default) | ||
| - "transparent": Transparent latch mode (immediate update) | ||
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| * ``adi,mode``: Sets the output mode | ||
| - "voltage": Voltage output mode (default) | ||
| - "current": Current output mode | ||
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| Device attributes | ||
| ================= | ||
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| The MAX22007 driver provides IIO DAC interfaces that vary based on the | ||
| configured channel mode. Each channel appears as a separate IIO device | ||
| attribute: | ||
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| * ``out_voltage_raw`` (voltage mode channels) | ||
| * ``out_current_raw`` (current mode channels) | ||
| * ``out_voltage_scale`` / ``out_current_scale`` (channel scaling factors) | ||
| * ``out_voltage_powermode`` / ``out_current_powermode`` (channel power control) | ||
| * ``out_voltage_powermode_available`` / ``out_current_powermode_available`` (available power modes) | ||
| * ``ldac_update`` (per-channel LDAC latch control) | ||
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| The driver automatically configures the IIO channel type based on the configured | ||
| channel mode from device tree. | ||
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| LDAC Update Control | ||
| =================== | ||
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| Each channel provides an ``ldac_update`` attribute for runtime LDAC (Latch DAC) | ||
| control. This allows precise timing control of when DAC register values are | ||
| transferred to the output: | ||
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| * Write ``1`` to trigger an immediate LDAC update for that specific channel | ||
| * Write ``0`` for no operation (returns immediately) | ||
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| This provides fine-grained control over output timing, which is essential for | ||
| applications requiring synchronized DAC updates. | ||
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| Power Mode Control | ||
| ================== | ||
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| Each channel provides ``powermode`` attributes for runtime power control: | ||
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| * Write ``"on"`` to enable the channel output | ||
| * Write ``"off"`` to disable the channel output | ||
| * Read the attribute to get the current power state | ||
| * Read ``powermode_available`` to see available power modes (always ``"off on"``) | ||
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| This allows individual channels to be powered on/off independently for power | ||
| management and safety purposes. | ||
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| Usage Examples | ||
| ============== | ||
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| Setting DAC output value and triggering LDAC update: | ||
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| .. code-block:: bash | ||
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| # Set channel 0 (voltage mode) to raw value 655 (≈2V) | ||
| echo 655 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw | ||
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| # Trigger LDAC update to apply the new value | ||
| echo 1 > /sys/bus/iio/devices/iio:deviceX/out_voltage0_ldac_update | ||
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| # Set channel 1 (current mode) and update | ||
| echo 1024 > /sys/bus/iio/devices/iio:deviceX/out_current1_raw | ||
| echo 1 > /sys/bus/iio/devices/iio:deviceX/out_current1_ldac_update | ||
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| Controlling channel power modes: | ||
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| .. code-block:: bash | ||
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| # Enable channel 0 | ||
| echo on > /sys/bus/iio/devices/iio:deviceX/out_voltage0_powermode | ||
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| # Disable channel 1 | ||
| echo off > /sys/bus/iio/devices/iio:deviceX/out_current1_powermode | ||
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| # Check current power state | ||
| cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_powermode | ||
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| # Check available power modes | ||
| cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_powermode_available | ||
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| Reading channel values and scale factors: | ||
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| .. code-block:: bash | ||
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| # Read raw DAC value | ||
| cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_raw | ||
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| # Read scale factor (volts per LSB) | ||
| cat /sys/bus/iio/devices/iio:deviceX/out_voltage0_scale | ||
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| Check available channels: | ||
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| .. code-block:: bash | ||
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| ls /sys/bus/iio/devices/iio:deviceX/out_*_raw | ||
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| Scale Calculations | ||
| ================== | ||
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| The driver provides accurate scale factors based on the hardware configuration: | ||
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| **Voltage Mode:** | ||
| - Scale = (5 × 2.5V) / 4096 = 0.003051757 V per LSB | ||
| - Range: 0V to 12.5V over 12-bit (0-4095) | ||
| - Formula: Output = Raw_Value × Scale | ||
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| **Current Mode:** | ||
| - Scale = (2.5V / (2 × 50Ω)) / 4096 = 0.000006103515625 A per LSB | ||
| - Range: 0A to 0.025A over 12-bit (0-4095) | ||
| - Formula: Output = Raw_Value × Scale | ||
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| Register Map | ||
| ------------ | ||
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| The MAX22007 uses the following register mapping: | ||
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| .. list-table:: | ||
| :header-rows: 1 | ||
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| * - Address | ||
| - Register Name | ||
| - Description | ||
| * - 0x03 | ||
| - CONFIG_REG | ||
| - Configuration register (CRC enable, DAC latch modes) | ||
| * - 0x04 | ||
| - CONTROL_REG | ||
| - LDAC control register for runtime updates | ||
| * - 0x05 | ||
| - CHANNEL_MODE_REG | ||
| - Channel mode and power control | ||
| * - 0x06 | ||
| - SOFT_RESET_REG | ||
| - Software reset control | ||
| * - 0x07-0x0A | ||
| - DAC_CHANNEL_REG(0-3) | ||
| - DAC data registers for channels 0-3 | ||
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| Driver Architecture | ||
| =================== | ||
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| The driver implements the following key features: | ||
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| * **CRC8 Error Checking**: All SPI communications use CRC8 for data integrity | ||
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| * **Channel Configuration**: Supports per-channel mode and power configuration | ||
| * **Register Map**: Uses regmap for efficient register access and caching | ||
| * **IIO Integration**: Full integration with the Linux IIO subsystem | ||
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| Not Implemented | ||
| =============== | ||
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| * Channel configuration (voltage/current mode) is set at device tree parsing | ||
| and cannot be changed dynamically | ||
| * The driver requires proper device tree configuration for optimal operation | ||
| * Simultaneous multi-channel LDAC updates (only single-channel updates supported) | ||
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I'm not getting the use case for this DAC latch control feature. Why not always driving the device in 'transparent' mode? We already have
out_voltageY_rawfor each channel. Why make the user write toout_voltageY_rawand toout_currentY_ldac_updateto get the DAC output updated? I'd just always write the proper bits toLD_CTRLwhenever the user writes toout_voltageY_raw.With that, I think
adi,dac-latch-modewill no longer be needed.There was a problem hiding this comment.
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Being it a per channel thing, I'm also not buying it (at least yet). AFAIR, typical case for this sort of thing is to for the latch mode to update all the channels at once which might be useful (in IIO) when buffering and update all channels at once. If we are only supporting raw writes I would (at least for now) just support transparent mode. Or do you have an actual request for this?