Documentation/hwmon/mcp9982.rst

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.. SPDX-License-Identifier: GPL-2.0+

Kernel driver MCP998X
=====================

Supported chips:

  * Microchip Technology MCP998X/MCP9933 and MCP998XD/MCP9933D

    Prefix: 'mcp9982'

    Datasheet:
    https://ww1.microchip.com/downloads/aemDocuments/documents/MSLD/ProductDocuments/DataSheets/MCP998X-Family-Data-Sheet-DS20006827.pdf

Authors:

   - Victor Duicu <victor.duicu@microchip.com>

Description
-----------

This driver implements support for the MCP998X family containing: MCP9982,
MCP9982D, MCP9983, MCP9983D, MCP9984, MCP9984D, MCP9985, MCP9985D,
MCP9933 and MCP9933D.

The MCP998X Family is a high accuracy 2-wire multichannel automotive
temperature monitor.

The chips in the family have different numbers of external channels,
ranging from 1 (MCP9982) to 4 channels (MCP9985). Reading diodes in
anti-parallel connection is supported by MCP9984/85/33 and
MCP9984D/85D/33D. Dedicated hardware shutdown circuitry is present
only in MCP998XD and MCP9933D.

Temperatures are read in millidegrees Celsius, ranging from -64 to
191.875 with 0.125 precision.

Each channel has a minimum, maximum, and critical limit alongside associated alarms.
The chips also implement a hysteresis mechanism which applies only to the maximum
and critical limits. The relative difference between a limit and its hysteresis
is the same for both and the value is kept in a single register.

The chips measure temperatures with a variable conversion rate.
Update_interval = Conversion/Second, so the available options are:
- 16000 (ms) = 1 conv/16 sec
- 8000 (ms) = 1 conv/8 sec
- 4000 (ms) = 1 conv/4 sec
- 2000 (ms) = 1 conv/2 sec
- 1000 (ms) = 1 conv/sec
- 500 (ms) = 2 conv/sec
- 250 (ms) = 4 conv/sec
- 125 (ms) = 8 conv/sec
- 64 (ms) = 16 conv/sec
- 32 (ms) = 32 conv/sec
- 16 (ms) = 64 conv/sec

Usage Notes
-----------

Parameters that can be configured in devicetree:
- anti-parallel diode mode operation
- resistance error correction on channels 1 and 2
- resistance error correction on channels 3 and 4
- power state

Chips 82/83 and 82D/83D do not support anti-parallel diode mode.
For chips with "D" in the name resistance error correction must be on.
Please see Documentation/devicetree/bindings/hwmon/microchip,mcp9982.yaml
for details.

Annotation

Implementation Notes