adt7462.rst (2525B)
1Kernel driver adt7462 2===================== 3 4Supported chips: 5 6 * Analog Devices ADT7462 7 8 Prefix: 'adt7462' 9 10 Addresses scanned: I2C 0x58, 0x5C 11 12 Datasheet: Publicly available at the Analog Devices website 13 14Author: Darrick J. Wong 15 16Description 17----------- 18 19This driver implements support for the Analog Devices ADT7462 chip family. 20 21This chip is a bit of a beast. It has 8 counters for measuring fan speed. It 22can also measure 13 voltages or 4 temperatures, or various combinations of the 23two. See the chip documentation for more details about the exact set of 24configurations. This driver does not allow one to configure the chip; that is 25left to the system designer. 26 27A sophisticated control system for the PWM outputs is designed into the ADT7462 28that allows fan speed to be adjusted automatically based on any of the three 29temperature sensors. Each PWM output is individually adjustable and 30programmable. Once configured, the ADT7462 will adjust the PWM outputs in 31response to the measured temperatures without further host intervention. This 32feature can also be disabled for manual control of the PWM's. 33 34Each of the measured inputs (voltage, temperature, fan speed) has 35corresponding high/low limit values. The ADT7462 will signal an ALARM if 36any measured value exceeds either limit. 37 38The ADT7462 samples all inputs continuously. The driver will not read 39the registers more often than once every other second. Further, 40configuration data is only read once per minute. 41 42Special Features 43---------------- 44 45The ADT7462 have a 10-bit ADC and can therefore measure temperatures 46with 0.25 degC resolution. 47 48The Analog Devices datasheet is very detailed and describes a procedure for 49determining an optimal configuration for the automatic PWM control. 50 51The driver will report sensor labels when it is able to determine that 52information from the configuration registers. 53 54Configuration Notes 55------------------- 56 57Besides 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 64 - point1: Set the pwm speed at a lower temperature bound. 65 - point2: Set the pwm speed at a higher temperature bound. 66 67The ADT7462 will scale the pwm between the lower and higher pwm speed when 68the temperature is between the two temperature boundaries. PWM values range 69from 0 (off) to 255 (full speed). Fan speed will be set to maximum when the 70temperature sensor associated with the PWM control exceeds temp#_max.