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Commit | Line | Data |
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7f15b664 RM |
1 | Kernel driver ds1621 |
2 | ==================== | |
3 | ||
4 | Supported chips: | |
cd6c8a42 | 5 | * Dallas Semiconductor / Maxim Integrated DS1621 |
7f15b664 | 6 | Prefix: 'ds1621' |
ed7c34e8 | 7 | Addresses scanned: none |
cd6c8a42 RC |
8 | Datasheet: Publicly available from www.maximintegrated.com |
9 | ||
7f15b664 | 10 | * Dallas Semiconductor DS1625 |
ed7c34e8 RC |
11 | Prefix: 'ds1625' |
12 | Addresses scanned: none | |
cd6c8a42 RC |
13 | Datasheet: Publicly available from www.datasheetarchive.com |
14 | ||
79c1cc1c RC |
15 | * Maxim Integrated DS1631 |
16 | Prefix: 'ds1631' | |
ed7c34e8 | 17 | Addresses scanned: none |
79c1cc1c RC |
18 | Datasheet: Publicly available from www.maximintegrated.com |
19 | ||
cd6c8a42 RC |
20 | * Maxim Integrated DS1721 |
21 | Prefix: 'ds1721' | |
ed7c34e8 | 22 | Addresses scanned: none |
cd6c8a42 | 23 | Datasheet: Publicly available from www.maximintegrated.com |
7f15b664 | 24 | |
260f81ff RC |
25 | * Maxim Integrated DS1731 |
26 | Prefix: 'ds1731' | |
27 | Addresses scanned: none | |
28 | Datasheet: Publicly available from www.maximintegrated.com | |
29 | ||
7f15b664 RM |
30 | Authors: |
31 | Christian W. Zuckschwerdt <zany@triq.net> | |
32 | valuable contributions by Jan M. Sendler <sendler@sendler.de> | |
33 | ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net> | |
7c81c60f | 34 | with the help of Jean Delvare <jdelvare@suse.de> |
7f15b664 RM |
35 | |
36 | Module Parameters | |
37 | ------------------ | |
38 | ||
39 | * polarity int | |
40 | Output's polarity: 0 = active high, 1 = active low | |
41 | ||
42 | Description | |
43 | ----------- | |
44 | ||
45 | The DS1621 is a (one instance) digital thermometer and thermostat. It has | |
46 | both high and low temperature limits which can be user defined (i.e. | |
47 | programmed into non-volatile on-chip registers). Temperature range is -55 | |
48 | degree Celsius to +125 in 0.5 increments. You may convert this into a | |
49 | Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity | |
50 | parameter is not provided, original value is used. | |
51 | ||
52 | As for the thermostat, behavior can also be programmed using the polarity | |
53 | toggle. On the one hand ("heater"), the thermostat output of the chip, | |
54 | Tout, will trigger when the low limit temperature is met or underrun and | |
55 | stays high until the high limit is met or exceeded. On the other hand | |
56 | ("cooler"), vice versa. That way "heater" equals "active low", whereas | |
57 | "conditioner" equals "active high". Please note that the DS1621 data sheet | |
58 | is somewhat misleading in this point since setting the polarity bit does | |
59 | not simply invert Tout. | |
60 | ||
61 | A second thing is that, during extensive testing, Tout showed a tolerance | |
62 | of up to +/- 0.5 degrees even when compared against precise temperature | |
63 | readings. Be sure to have a high vs. low temperature limit gap of al least | |
64 | 1.0 degree Celsius to avoid Tout "bouncing", though! | |
65 | ||
25f3311a JD |
66 | The alarm bits are set when the high or low limits are met or exceeded and |
67 | are reset by the module as soon as the respective temperature ranges are | |
68 | left. | |
7f15b664 RM |
69 | |
70 | The alarm registers are in no way suitable to find out about the actual | |
71 | status of Tout. They will only tell you about its history, whether or not | |
72 | any of the limits have ever been met or exceeded since last power-up or | |
73 | reset. Be aware: When testing, it showed that the status of Tout can change | |
74 | with neither of the alarms set. | |
75 | ||
ed7c34e8 RC |
76 | Since there is no version or vendor identification register, there is |
77 | no unique identification for these devices. Therefore, explicit device | |
87438c2c RC |
78 | instantiation is required for correct device identification and functionality |
79 | (one device per address in this address range: 0x48..0x4f). | |
cd6c8a42 | 80 | |
87438c2c RC |
81 | The DS1625 is pin compatible and functionally equivalent with the DS1621, |
82 | but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are | |
83 | also pin compatible with the DS1621 and provide multi-resolution support. | |
84 | ||
85 | Additionally, the DS1721 data sheet says the temperature flags (THF and TLF) | |
86 | are used internally, however, these flags do get set and cleared as the actual | |
87 | temperature crosses the min or max settings (which by default are set to 75 | |
88 | and 80 degrees respectively). | |
89 | ||
90 | Temperature Conversion: | |
91 | ----------------------- | |
92 | DS1621 - 750ms (older devices may take up to 1000ms) | |
93 | DS1625 - 500ms | |
94 | DS1631 - 93ms..750ms for 9..12 bits resolution, respectively. | |
95 | DS1721 - 93ms..750ms for 9..12 bits resolution, respectively. | |
96 | DS1731 - 93ms..750ms for 9..12 bits resolution, respectively. | |
97 | ||
98 | Note: | |
99 | On the DS1621, internal access to non-volatile registers may last for 10ms | |
100 | or less (unverified on the other devices). | |
101 | ||
102 | Temperature Accuracy: | |
103 | --------------------- | |
104 | DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees) | |
105 | DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees) | |
106 | DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees) | |
107 | DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees) | |
108 | DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees) | |
109 | ||
110 | Note: | |
111 | Please refer to the device datasheets for accuracy at other temperatures. | |
112 | ||
113 | Temperature Resolution: | |
114 | ----------------------- | |
115 | As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution | |
116 | support, which is achieved via the R0 and R1 config register bits, where: | |
117 | ||
118 | R0..R1 | |
119 | ------ | |
120 | 0 0 => 9 bits, 0.5 degrees Celcius | |
121 | 1 0 => 10 bits, 0.25 degrees Celcius | |
122 | 0 1 => 11 bits, 0.125 degrees Celcius | |
123 | 1 1 => 12 bits, 0.0625 degrees Celcius | |
124 | ||
125 | Note: | |
126 | At initial device power-on, the default resolution is set to 12-bits. | |
3a8fe331 | 127 | |
260f81ff RC |
128 | The resolution mode for the DS1631, DS1721, or DS1731 can be changed from |
129 | userspace, via the device 'update_interval' sysfs attribute. This attribute | |
130 | will normalize the range of input values to the device maximum resolution | |
131 | values defined in the datasheet as follows: | |
3a8fe331 RC |
132 | |
133 | Resolution Conversion Time Input Range | |
134 | (C/LSB) (msec) (msec) | |
87438c2c | 135 | ------------------------------------------------ |
3a8fe331 RC |
136 | 0.5 93.75 0....94 |
137 | 0.25 187.5 95...187 | |
138 | 0.125 375 188..375 | |
139 | 0.0625 750 376..infinity | |
87438c2c | 140 | ------------------------------------------------ |
3a8fe331 RC |
141 | |
142 | The following examples show how the 'update_interval' attribute can be | |
143 | used to change the conversion time: | |
144 | ||
145 | $ cat update_interval | |
146 | 750 | |
147 | $ cat temp1_input | |
148 | 22062 | |
149 | $ | |
150 | $ echo 300 > update_interval | |
151 | $ cat update_interval | |
152 | 375 | |
153 | $ cat temp1_input | |
154 | 22125 | |
155 | $ | |
156 | $ echo 150 > update_interval | |
157 | $ cat update_interval | |
158 | 188 | |
159 | $ cat temp1_input | |
160 | 22250 | |
161 | $ | |
162 | $ echo 1 > update_interval | |
163 | $ cat update_interval | |
164 | 94 | |
165 | $ cat temp1_input | |
166 | 22000 | |
167 | $ | |
168 | $ echo 1000 > update_interval | |
169 | $ cat update_interval | |
170 | 750 | |
171 | $ cat temp1_input | |
172 | 22062 | |
173 | $ | |
174 | ||
175 | As shown, the ds1621 driver automatically adjusts the 'update_interval' | |
176 | user input, via a step function. Reading back the 'update_interval' value | |
177 | after a write operation provides the conversion time used by the device. | |
178 | ||
179 | Mathematically, the resolution can be derived from the conversion time | |
180 | via the following function: | |
181 | ||
182 | g(x) = 0.5 * [minimum_conversion_time/x] | |
183 | ||
184 | where: | |
185 | -> 'x' = the output from 'update_interval' | |
186 | -> 'g(x)' = the resolution in degrees C per LSB. | |
187 | -> 93.75ms = minimum conversion time |