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Commit | Line | Data |
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7f15b664 RM |
1 | Kernel driver ds1621 |
2 | ==================== | |
3 | ||
4 | Supported chips: | |
b04f2f7d | 5 | |
cd6c8a42 | 6 | * Dallas Semiconductor / Maxim Integrated DS1621 |
b04f2f7d | 7 | |
7f15b664 | 8 | Prefix: 'ds1621' |
b04f2f7d | 9 | |
ed7c34e8 | 10 | Addresses scanned: none |
b04f2f7d | 11 | |
cd6c8a42 RC |
12 | Datasheet: Publicly available from www.maximintegrated.com |
13 | ||
7f15b664 | 14 | * Dallas Semiconductor DS1625 |
b04f2f7d | 15 | |
ed7c34e8 | 16 | Prefix: 'ds1625' |
b04f2f7d | 17 | |
ed7c34e8 | 18 | Addresses scanned: none |
b04f2f7d | 19 | |
cd6c8a42 RC |
20 | Datasheet: Publicly available from www.datasheetarchive.com |
21 | ||
79c1cc1c | 22 | * Maxim Integrated DS1631 |
b04f2f7d | 23 | |
79c1cc1c | 24 | Prefix: 'ds1631' |
b04f2f7d | 25 | |
ed7c34e8 | 26 | Addresses scanned: none |
b04f2f7d | 27 | |
79c1cc1c RC |
28 | Datasheet: Publicly available from www.maximintegrated.com |
29 | ||
cd6c8a42 | 30 | * Maxim Integrated DS1721 |
b04f2f7d | 31 | |
cd6c8a42 | 32 | Prefix: 'ds1721' |
b04f2f7d | 33 | |
ed7c34e8 | 34 | Addresses scanned: none |
b04f2f7d | 35 | |
cd6c8a42 | 36 | Datasheet: Publicly available from www.maximintegrated.com |
7f15b664 | 37 | |
260f81ff | 38 | * Maxim Integrated DS1731 |
b04f2f7d | 39 | |
260f81ff | 40 | Prefix: 'ds1731' |
b04f2f7d | 41 | |
260f81ff | 42 | Addresses scanned: none |
b04f2f7d | 43 | |
260f81ff RC |
44 | Datasheet: Publicly available from www.maximintegrated.com |
45 | ||
7f15b664 | 46 | Authors: |
b04f2f7d MCC |
47 | - Christian W. Zuckschwerdt <zany@triq.net> |
48 | - valuable contributions by Jan M. Sendler <sendler@sendler.de> | |
49 | - ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net> | |
50 | with the help of Jean Delvare <jdelvare@suse.de> | |
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51 | |
52 | Module Parameters | |
53 | ------------------ | |
54 | ||
55 | * polarity int | |
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56 | Output's polarity: |
57 | ||
58 | * 0 = active high, | |
59 | * 1 = active low | |
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60 | |
61 | Description | |
62 | ----------- | |
63 | ||
64 | The DS1621 is a (one instance) digital thermometer and thermostat. It has | |
65 | both high and low temperature limits which can be user defined (i.e. | |
66 | programmed into non-volatile on-chip registers). Temperature range is -55 | |
67 | degree Celsius to +125 in 0.5 increments. You may convert this into a | |
68 | Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity | |
69 | parameter is not provided, original value is used. | |
70 | ||
71 | As for the thermostat, behavior can also be programmed using the polarity | |
72 | toggle. On the one hand ("heater"), the thermostat output of the chip, | |
73 | Tout, will trigger when the low limit temperature is met or underrun and | |
74 | stays high until the high limit is met or exceeded. On the other hand | |
75 | ("cooler"), vice versa. That way "heater" equals "active low", whereas | |
76 | "conditioner" equals "active high". Please note that the DS1621 data sheet | |
77 | is somewhat misleading in this point since setting the polarity bit does | |
78 | not simply invert Tout. | |
79 | ||
80 | A second thing is that, during extensive testing, Tout showed a tolerance | |
81 | of up to +/- 0.5 degrees even when compared against precise temperature | |
82 | readings. Be sure to have a high vs. low temperature limit gap of al least | |
83 | 1.0 degree Celsius to avoid Tout "bouncing", though! | |
84 | ||
25f3311a JD |
85 | The alarm bits are set when the high or low limits are met or exceeded and |
86 | are reset by the module as soon as the respective temperature ranges are | |
87 | left. | |
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88 | |
89 | The alarm registers are in no way suitable to find out about the actual | |
90 | status of Tout. They will only tell you about its history, whether or not | |
91 | any of the limits have ever been met or exceeded since last power-up or | |
92 | reset. Be aware: When testing, it showed that the status of Tout can change | |
93 | with neither of the alarms set. | |
94 | ||
ed7c34e8 RC |
95 | Since there is no version or vendor identification register, there is |
96 | no unique identification for these devices. Therefore, explicit device | |
87438c2c RC |
97 | instantiation is required for correct device identification and functionality |
98 | (one device per address in this address range: 0x48..0x4f). | |
cd6c8a42 | 99 | |
87438c2c RC |
100 | The DS1625 is pin compatible and functionally equivalent with the DS1621, |
101 | but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are | |
102 | also pin compatible with the DS1621 and provide multi-resolution support. | |
103 | ||
104 | Additionally, the DS1721 data sheet says the temperature flags (THF and TLF) | |
105 | are used internally, however, these flags do get set and cleared as the actual | |
106 | temperature crosses the min or max settings (which by default are set to 75 | |
107 | and 80 degrees respectively). | |
108 | ||
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109 | Temperature Conversion |
110 | ---------------------- | |
111 | ||
112 | - DS1621 - 750ms (older devices may take up to 1000ms) | |
113 | - DS1625 - 500ms | |
114 | - DS1631 - 93ms..750ms for 9..12 bits resolution, respectively. | |
115 | - DS1721 - 93ms..750ms for 9..12 bits resolution, respectively. | |
116 | - DS1731 - 93ms..750ms for 9..12 bits resolution, respectively. | |
87438c2c RC |
117 | |
118 | Note: | |
119 | On the DS1621, internal access to non-volatile registers may last for 10ms | |
120 | or less (unverified on the other devices). | |
121 | ||
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122 | Temperature Accuracy |
123 | -------------------- | |
87438c2c | 124 | |
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125 | - DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees) |
126 | - DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees) | |
127 | - DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees) | |
128 | - DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees) | |
129 | - DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees) | |
130 | ||
131 | .. Note:: | |
132 | ||
133 | Please refer to the device datasheets for accuracy at other temperatures. | |
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134 | |
135 | Temperature Resolution: | |
136 | ----------------------- | |
137 | As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution | |
138 | support, which is achieved via the R0 and R1 config register bits, where: | |
139 | ||
140 | R0..R1 | |
141 | ------ | |
87438c2c | 142 | |
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143 | == == =============================== |
144 | R0 R1 | |
145 | == == =============================== | |
146 | 0 0 9 bits, 0.5 degrees Celsius | |
147 | 1 0 10 bits, 0.25 degrees Celsius | |
148 | 0 1 11 bits, 0.125 degrees Celsius | |
149 | 1 1 12 bits, 0.0625 degrees Celsius | |
150 | == == =============================== | |
151 | ||
152 | .. Note:: | |
153 | ||
154 | At initial device power-on, the default resolution is set to 12-bits. | |
3a8fe331 | 155 | |
260f81ff RC |
156 | The resolution mode for the DS1631, DS1721, or DS1731 can be changed from |
157 | userspace, via the device 'update_interval' sysfs attribute. This attribute | |
158 | will normalize the range of input values to the device maximum resolution | |
159 | values defined in the datasheet as follows: | |
3a8fe331 | 160 | |
b04f2f7d | 161 | ============= ================== =============== |
3a8fe331 RC |
162 | Resolution Conversion Time Input Range |
163 | (C/LSB) (msec) (msec) | |
b04f2f7d | 164 | ============= ================== =============== |
3a8fe331 RC |
165 | 0.5 93.75 0....94 |
166 | 0.25 187.5 95...187 | |
167 | 0.125 375 188..375 | |
168 | 0.0625 750 376..infinity | |
b04f2f7d | 169 | ============= ================== =============== |
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170 | |
171 | The following examples show how the 'update_interval' attribute can be | |
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172 | used to change the conversion time:: |
173 | ||
174 | $ cat update_interval | |
175 | 750 | |
176 | $ cat temp1_input | |
177 | 22062 | |
178 | $ | |
179 | $ echo 300 > update_interval | |
180 | $ cat update_interval | |
181 | 375 | |
182 | $ cat temp1_input | |
183 | 22125 | |
184 | $ | |
185 | $ echo 150 > update_interval | |
186 | $ cat update_interval | |
187 | 188 | |
188 | $ cat temp1_input | |
189 | 22250 | |
190 | $ | |
191 | $ echo 1 > update_interval | |
192 | $ cat update_interval | |
193 | 94 | |
194 | $ cat temp1_input | |
195 | 22000 | |
196 | $ | |
197 | $ echo 1000 > update_interval | |
198 | $ cat update_interval | |
199 | 750 | |
200 | $ cat temp1_input | |
201 | 22062 | |
202 | $ | |
3a8fe331 RC |
203 | |
204 | As shown, the ds1621 driver automatically adjusts the 'update_interval' | |
205 | user input, via a step function. Reading back the 'update_interval' value | |
206 | after a write operation provides the conversion time used by the device. | |
207 | ||
208 | Mathematically, the resolution can be derived from the conversion time | |
209 | via the following function: | |
210 | ||
211 | g(x) = 0.5 * [minimum_conversion_time/x] | |
212 | ||
213 | where: | |
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214 | |
215 | - 'x' = the output from 'update_interval' | |
216 | - 'g(x)' = the resolution in degrees C per LSB. | |
217 | - 93.75ms = minimum conversion time |