| Kernel driver adt7473 | |
| ====================== | |
| Supported chips: | |
| * Analog Devices ADT7473 | |
| Prefix: 'adt7473' | |
| Addresses scanned: I2C 0x2C, 0x2D, 0x2E | |
| Datasheet: Publicly available at the Analog Devices website | |
| Author: Darrick J. Wong | |
| Description | |
| ----------- | |
| This driver implements support for the Analog Devices ADT7473 chip family. | |
| The ADT7473 uses the 2-wire interface compatible with the SMBUS 2.0 | |
| specification. Using an analog to digital converter it measures three (3) | |
| temperatures and two (2) voltages. It has four (4) 16-bit counters for | |
| measuring fan speed. There are three (3) PWM outputs that can be used | |
| to control fan speed. | |
| A sophisticated control system for the PWM outputs is designed into the | |
| ADT7473 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 ADT7473 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 ADT7473 will signal an ALARM if | |
| any measured value exceeds either limit. | |
| The ADT7473 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 ADT7473 have a 10-bit ADC and can therefore measure temperatures | |
| with 0.25 degC resolution. Temperature readings can be configured either | |
| for twos complement format or "Offset 64" format, wherein 63 is subtracted | |
| from the raw value to get the temperature value. | |
| 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 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 ADT7473 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. | |
| Notes | |
| ----- | |
| The NVIDIA binary driver presents an ADT7473 chip via an on-card i2c bus. | |
| Unfortunately, they fail to set the i2c adapter class, so this driver may | |
| fail to find the chip until the nvidia driver is patched. |