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Based on kernel version 3.16. Page generated on 2014-08-06 21:39 EST.

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