[linux.git] / Documentation / hwmon / adt7462.rst

Kernel driver adt7462
=====================

Supported chips:

  * Analog Devices ADT7462

    Prefix: 'adt7462'

    Addresses scanned: I2C 0x58, 0x5C

    Datasheet: Publicly available at the Analog Devices website

Author: Darrick J. Wong

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

This driver implements support for the Analog Devices ADT7462 chip family.

This chip is a bit of a beast.  It has 8 counters for measuring fan speed.  It
can also measure 13 voltages or 4 temperatures, or various combinations of the
two.  See the chip documentation for more details about the exact set of
configurations.  This driver does not allow one to configure the chip; that is
left to the system designer.

A sophisticated control system for the PWM outputs is designed into the ADT7462
that allows fan speed to be adjusted automatically based on any of the three
temperature sensors. Each PWM output is individually adjustable and
programmable. Once configured, the ADT7462 will adjust the PWM outputs in
response to the measured temperatures without further host intervention.  This
feature can also be disabled for manual control of the PWM's.

Each of the measured inputs (voltage, temperature, fan speed) has
corresponding high/low limit values. The ADT7462 will signal an ALARM if
any measured value exceeds either limit.

The ADT7462 samples all inputs continuously. The driver will not read
the registers more often than once every other second. Further,
configuration data is only read once per minute.

Special Features
----------------

The ADT7462 have a 10-bit ADC and can therefore measure temperatures
with 0.25 degC resolution.

The Analog Devices datasheet is very detailed and describes a procedure for
determining an optimal configuration for the automatic PWM control.

The driver will report sensor labels when it is able to determine that
information from the configuration registers.

Configuration Notes
-------------------

Besides standard interfaces driver adds the following:

* PWM Control

* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
* pwm#_auto_point2_pwm and temp#_auto_point2_temp -

  - point1: Set the pwm speed at a lower temperature bound.
  - point2: Set the pwm speed at a higher temperature bound.

The ADT7462 will scale the pwm between the lower and higher pwm speed when
the temperature is between the two temperature boundaries.  PWM values range
from 0 (off) to 255 (full speed).  Fan speed will be set to maximum when the
temperature sensor associated with the PWM control exceeds temp#_max.
Commit	Line	Data
c0b4e3ab	1	Kernel driver adt7462
b04f2f7d	2	=====================
c0b4e3ab DW	3
c0b4e3ab DW	4	Supported chips:
b04f2f7d	5
c0b4e3ab	6	* Analog Devices ADT7462
b04f2f7d	7
c0b4e3ab	8	Prefix: 'adt7462'
b04f2f7d	9
c0b4e3ab	10	Addresses scanned: I2C 0x58, 0x5C
b04f2f7d	11
c0b4e3ab DW	12	Datasheet: Publicly available at the Analog Devices website
	13
	14	Author: Darrick J. Wong
	15
	16	Description
	17	-----------
	18
	19	This driver implements support for the Analog Devices ADT7462 chip family.
	20
	21	This chip is a bit of a beast. It has 8 counters for measuring fan speed. It
	22	can also measure 13 voltages or 4 temperatures, or various combinations of the
	23	two. See the chip documentation for more details about the exact set of
	24	configurations. This driver does not allow one to configure the chip; that is
	25	left to the system designer.
	26
	27	A sophisticated control system for the PWM outputs is designed into the ADT7462
	28	that allows fan speed to be adjusted automatically based on any of the three
	29	temperature sensors. Each PWM output is individually adjustable and
	30	programmable. Once configured, the ADT7462 will adjust the PWM outputs in
	31	response to the measured temperatures without further host intervention. This
	32	feature can also be disabled for manual control of the PWM's.
	33
	34	Each of the measured inputs (voltage, temperature, fan speed) has
	35	corresponding high/low limit values. The ADT7462 will signal an ALARM if
	36	any measured value exceeds either limit.
	37
	38	The ADT7462 samples all inputs continuously. The driver will not read
	39	the registers more often than once every other second. Further,
	40	configuration data is only read once per minute.
	41
	42	Special Features
	43	----------------
	44
	45	The ADT7462 have a 10-bit ADC and can therefore measure temperatures
	46	with 0.25 degC resolution.
	47
	48	The Analog Devices datasheet is very detailed and describes a procedure for
	49	determining an optimal configuration for the automatic PWM control.
	50
	51	The driver will report sensor labels when it is able to determine that
	52	information from the configuration registers.
	53
	54	Configuration Notes
	55	-------------------
	56
	57	Besides standard interfaces driver adds the following:
	58
	59	* PWM Control
	60
	61	* pwm#_auto_point1_pwm and temp#_auto_point1_temp and
	62	* pwm#_auto_point2_pwm and temp#_auto_point2_temp -
	63
b04f2f7d MCC	64	- point1: Set the pwm speed at a lower temperature bound.
b04f2f7d MCC	65	- point2: Set the pwm speed at a higher temperature bound.
c0b4e3ab DW	66
	67	The ADT7462 will scale the pwm between the lower and higher pwm speed when
	68	the temperature is between the two temperature boundaries. PWM values range
	69	from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the
	70	temperature sensor associated with the PWM control exceeds temp#_max.