linux/Documentation/hwmon/adt7470
<<
>>
Prefs
   1Kernel driver adt7470
   2=====================
   3
   4Supported chips:
   5  * Analog Devices ADT7470
   6    Prefix: 'adt7470'
   7    Addresses scanned: I2C 0x2C, 0x2E, 0x2F
   8    Datasheet: Publicly available at the Analog Devices website
   9
  10Author: Darrick J. Wong
  11
  12Description
  13-----------
  14
  15This driver implements support for the Analog Devices ADT7470 chip.  There may
  16be other chips that implement this interface.
  17
  18The ADT7470 uses the 2-wire interface compatible with the SMBus 2.0
  19specification. Using an analog to digital converter it measures up to ten (10)
  20external temperatures. It has four (4) 16-bit counters for measuring fan speed.
  21There are four (4) PWM outputs that can be used to control fan speed.
  22
  23A sophisticated control system for the PWM outputs is designed into the ADT7470
  24that allows fan speed to be adjusted automatically based on any of the ten
  25temperature sensors. Each PWM output is individually adjustable and
  26programmable. Once configured, the ADT7470 will adjust the PWM outputs in
  27response to the measured temperatures with further host intervention.  This
  28feature can also be disabled for manual control of the PWM's.
  29
  30Each of the measured inputs (temperature, fan speed) has corresponding high/low
  31limit values. The ADT7470 will signal an ALARM if any measured value exceeds
  32either limit.
  33
  34The ADT7470 samples all inputs continuously.  A kernel thread is started up for
  35the purpose of periodically querying the temperature sensors, thus allowing the
  36automatic fan pwm control to set the fan speed.  The driver will not read the
  37registers more often than once every 5 seconds.  Further, configuration data is
  38only read once per minute.
  39
  40Special Features
  41----------------
  42
  43The ADT7470 has a 8-bit ADC and is capable of measuring temperatures with 1
  44degC resolution.
  45
  46The Analog Devices datasheet is very detailed and describes a procedure for
  47determining an optimal configuration for the automatic PWM control.
  48
  49Configuration Notes
  50-------------------
  51
  52Besides standard interfaces driver adds the following:
  53
  54* PWM Control
  55
  56* pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
  57* pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
  58
  59point1: Set the pwm speed at a lower temperature bound.
  60point2: Set the pwm speed at a higher temperature bound.
  61
  62The ADT7470 will scale the pwm between the lower and higher pwm speed when
  63the temperature is between the two temperature boundaries.  PWM values range
  64from 0 (off) to 255 (full speed).  Fan speed will be set to maximum when the
  65temperature sensor associated with the PWM control exceeds
  66pwm#_auto_point2_temp.
  67
  68Notes
  69-----
  70
  71The temperature inputs no longer need to be read periodically from userspace in
  72order for the automatic pwm algorithm to run.  This was the case for earlier
  73versions of the driver.
  74
lxr.linux.no kindly hosted by Redpill Linpro AS, provider of Linux consulting and operations services since 1995.