| 12345678910111213141516171819202122232425262728293031323334353637383940414243444546474849505152535455565758596061626364656667686970717273747576 |
- Kernel driver adt7470
- =====================
- Supported chips:
- * Analog Devices ADT7470
- Prefix: 'adt7470'
- Addresses scanned: I2C 0x2C, 0x2E, 0x2F
- Datasheet: Publicly available at the Analog Devices website
- Author: Darrick J. Wong
- Description
- -----------
- This driver implements support for the Analog Devices ADT7470 chip. There may
- be other chips that implement this interface.
- The ADT7470 uses the 2-wire interface compatible with the SMBus 2.0
- specification. Using an analog to digital converter it measures up to ten (10)
- external temperatures. It has four (4) 16-bit counters for measuring fan speed.
- There are four (4) PWM outputs that can be used to control fan speed.
- A sophisticated control system for the PWM outputs is designed into the ADT7470
- that allows fan speed to be adjusted automatically based on any of the ten
- temperature sensors. Each PWM output is individually adjustable and
- programmable. Once configured, the ADT7470 will adjust the PWM outputs in
- response to the measured temperatures with further host intervention. This
- feature can also be disabled for manual control of the PWM's.
- Each of the measured inputs (temperature, fan speed) has corresponding high/low
- limit values. The ADT7470 will signal an ALARM if any measured value exceeds
- either limit.
- The ADT7470 DOES NOT sample all inputs continuously. A single pin on the
- ADT7470 is connected to a multitude of thermal diodes, but the chip must be
- instructed explicitly to read the multitude of diodes. If you want to use
- automatic fan control mode, you must manually read any of the temperature
- sensors or the fan control algorithm will not run. The chip WILL NOT DO THIS
- AUTOMATICALLY; this must be done from userspace. This may be a bug in the chip
- design, given that many other AD chips take care of this. The driver will not
- read the registers more often than once every 5 seconds. Further,
- configuration data is only read once per minute.
- Special Features
- ----------------
- The ADT7470 has a 8-bit ADC and is capable of measuring temperatures with 1
- degC resolution.
- The Analog Devices datasheet is very detailed and describes a procedure for
- determining an optimal configuration for the automatic PWM control.
- Configuration Notes
- -------------------
- Besides standard interfaces driver adds the following:
- * PWM Control
- * pwm#_auto_point1_pwm and pwm#_auto_point1_temp and
- * pwm#_auto_point2_pwm and pwm#_auto_point2_temp -
- point1: Set the pwm speed at a lower temperature bound.
- point2: Set the pwm speed at a higher temperature bound.
- The ADT7470 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
- pwm#_auto_point2_temp.
- Notes
- -----
- As stated above, the temperature inputs must be read periodically from
- userspace in order for the automatic pwm algorithm to run.
|
