Based on kernel version 2.6.26. Page generated on 2008-07-16 21:12 EST.
1 Kernel driver adt7473 2 ====================== 3 4 Supported chips: 5 * Analog Devices ADT7473 6 Prefix: 'adt7473' 7 Addresses scanned: I2C 0x2C, 0x2D, 0x2E 8 Datasheet: Publicly available at the Analog Devices website 9 10 Author: Darrick J. Wong 11 12 Description 13 ----------- 14 15 This driver implements support for the Analog Devices ADT7473 chip family. 16 17 The LM85 uses the 2-wire interface compatible with the SMBUS 2.0 18 specification. Using an analog to digital converter it measures three (3) 19 temperatures and two (2) voltages. It has three (3) 16-bit counters for 20 measuring fan speed. There are three (3) PWM outputs that can be used 21 to control fan speed. 22 23 A sophisticated control system for the PWM outputs is designed into the 24 LM85 that allows fan speed to be adjusted automatically based on any of the 25 three temperature sensors. Each PWM output is individually adjustable and 26 programmable. Once configured, the ADT7473 will adjust the PWM outputs in 27 response to the measured temperatures without further host intervention. 28 This feature can also be disabled for manual control of the PWM's. 29 30 Each of the measured inputs (voltage, temperature, fan speed) has 31 corresponding high/low limit values. The ADT7473 will signal an ALARM if 32 any measured value exceeds either limit. 33 34 The ADT7473 samples all inputs continuously. The driver will not read 35 the registers more often than once every other second. Further, 36 configuration data is only read once per minute. 37 38 Special Features 39 ---------------- 40 41 The ADT7473 have a 10-bit ADC and can therefore measure temperatures 42 with 0.25 degC resolution. Temperature readings can be configured either 43 for twos complement format or "Offset 64" format, wherein 63 is subtracted 44 from the raw value to get the temperature value. 45 46 The Analog Devices datasheet is very detailed and describes a procedure for 47 determining an optimal configuration for the automatic PWM control. 48 49 Hardware Configurations 50 ----------------------- 51 52 The ADT7473 chips have an optional SMBALERT output that can be used to 53 signal the chipset in case a limit is exceeded or the temperature sensors 54 fail. Individual sensor interrupts can be masked so they won't trigger 55 SMBALERT. The SMBALERT output if configured replaces the PWM2 function. 56 57 Configuration Notes 58 ------------------- 59 60 Besides standard interfaces driver adds the following: 61 62 * PWM Control 63 64 * pwm#_auto_point1_pwm and pwm#_auto_point1_temp and 65 * pwm#_auto_point2_pwm and pwm#_auto_point2_temp - 66 67 point1: Set the pwm speed at a lower temperature bound. 68 point2: Set the pwm speed at a higher temperature bound. 69 70 The ADT7473 will scale the pwm between the lower and higher pwm speed when 71 the temperature is between the two temperature boundaries. PWM values range 72 from 0 (off) to 255 (full speed). 73 74 Notes 75 ----- 76 77 The NVIDIA binary driver presents an ADT7473 chip via an on-card i2c bus. 78 Unfortunately, they fail to set the i2c adapter class, so this driver may 79 fail to find the chip until the nvidia driver is patched.