1 Kernel driver ds1621 1 Kernel driver ds1621
2 ==================== 2 ====================
3 3
4 Supported chips: 4 Supported chips:
5 5
6 * Dallas Semiconductor / Maxim Integrated DS 6 * Dallas Semiconductor / Maxim Integrated DS1621
7 7
8 Prefix: 'ds1621' 8 Prefix: 'ds1621'
9 9
10 Addresses scanned: none 10 Addresses scanned: none
11 11
12 Datasheet: Publicly available from www.max 12 Datasheet: Publicly available from www.maximintegrated.com
13 13
14 * Dallas Semiconductor DS1625 14 * Dallas Semiconductor DS1625
15 15
16 Prefix: 'ds1625' 16 Prefix: 'ds1625'
17 17
18 Addresses scanned: none 18 Addresses scanned: none
19 19
20 Datasheet: Publicly available from www.dat 20 Datasheet: Publicly available from www.datasheetarchive.com
21 21
22 * Maxim Integrated DS1631 22 * Maxim Integrated DS1631
23 23
24 Prefix: 'ds1631' 24 Prefix: 'ds1631'
25 25
26 Addresses scanned: none 26 Addresses scanned: none
27 27
28 Datasheet: Publicly available from www.max 28 Datasheet: Publicly available from www.maximintegrated.com
29 29
30 * Maxim Integrated DS1721 30 * Maxim Integrated DS1721
31 31
32 Prefix: 'ds1721' 32 Prefix: 'ds1721'
33 33
34 Addresses scanned: none 34 Addresses scanned: none
35 35
36 Datasheet: Publicly available from www.max 36 Datasheet: Publicly available from www.maximintegrated.com
37 37
38 * Maxim Integrated DS1731 38 * Maxim Integrated DS1731
39 39
40 Prefix: 'ds1731' 40 Prefix: 'ds1731'
41 41
42 Addresses scanned: none 42 Addresses scanned: none
43 43
44 Datasheet: Publicly available from www.max 44 Datasheet: Publicly available from www.maximintegrated.com
45 45
46 Authors: 46 Authors:
47 - Christian W. Zuckschwerdt <zany@triq.ne 47 - Christian W. Zuckschwerdt <zany@triq.net>
48 - valuable contributions by Jan M. Sendl< 48 - valuable contributions by Jan M. Sendler <sendler@sendler.de>
49 - ported to 2.6 by Aurelien Jarno <aureli 49 - ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net>
50 with the help of Jean Delvare <jdelvare 50 with the help of Jean Delvare <jdelvare@suse.de>
51 51
52 Module Parameters 52 Module Parameters
53 ------------------ 53 ------------------
54 54
55 * polarity int 55 * polarity int
56 Output's polarity: 56 Output's polarity:
57 57
58 * 0 = active high, 58 * 0 = active high,
59 * 1 = active low 59 * 1 = active low
60 60
61 Description 61 Description
62 ----------- 62 -----------
63 63
64 The DS1621 is a (one instance) digital thermom 64 The DS1621 is a (one instance) digital thermometer and thermostat. It has
65 both high and low temperature limits which can 65 both high and low temperature limits which can be user defined (i.e.
66 programmed into non-volatile on-chip registers 66 programmed into non-volatile on-chip registers). Temperature range is -55
67 degree Celsius to +125 in 0.5 increments. You 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 68 Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity
69 parameter is not provided, original value is u 69 parameter is not provided, original value is used.
70 70
71 As for the thermostat, behavior can also be pr 71 As for the thermostat, behavior can also be programmed using the polarity
72 toggle. On the one hand ("heater"), the thermo 72 toggle. On the one hand ("heater"), the thermostat output of the chip,
73 Tout, will trigger when the low limit temperat 73 Tout, will trigger when the low limit temperature is met or underrun and
74 stays high until the high limit is met or exce 74 stays high until the high limit is met or exceeded. On the other hand
75 ("cooler"), vice versa. That way "heater" equa 75 ("cooler"), vice versa. That way "heater" equals "active low", whereas
76 "conditioner" equals "active high". Please not 76 "conditioner" equals "active high". Please note that the DS1621 data sheet
77 is somewhat misleading in this point since set 77 is somewhat misleading in this point since setting the polarity bit does
78 not simply invert Tout. 78 not simply invert Tout.
79 79
80 A second thing is that, during extensive testi 80 A second thing is that, during extensive testing, Tout showed a tolerance
81 of up to +/- 0.5 degrees even when compared ag 81 of up to +/- 0.5 degrees even when compared against precise temperature
82 readings. Be sure to have a high vs. low tempe 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", t 83 1.0 degree Celsius to avoid Tout "bouncing", though!
84 84
85 The alarm bits are set when the high or low li 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 respect 86 are reset by the module as soon as the respective temperature ranges are
87 left. 87 left.
88 88
89 The alarm registers are in no way suitable to 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 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 exceed 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 92 reset. Be aware: When testing, it showed that the status of Tout can change
93 with neither of the alarms set. 93 with neither of the alarms set.
94 94
95 Since there is no version or vendor identifica 95 Since there is no version or vendor identification register, there is
96 no unique identification for these devices. Th 96 no unique identification for these devices. Therefore, explicit device
97 instantiation is required for correct device i 97 instantiation is required for correct device identification and functionality
98 (one device per address in this address range: 98 (one device per address in this address range: 0x48..0x4f).
99 99
100 The DS1625 is pin compatible and functionally 100 The DS1625 is pin compatible and functionally equivalent with the DS1621,
101 but the DS1621 is meant to replace it. The DS1 101 but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are
102 also pin compatible with the DS1621 and provid 102 also pin compatible with the DS1621 and provide multi-resolution support.
103 103
104 Additionally, the DS1721 data sheet says the t 104 Additionally, the DS1721 data sheet says the temperature flags (THF and TLF)
105 are used internally, however, these flags do g 105 are used internally, however, these flags do get set and cleared as the actual
106 temperature crosses the min or max settings (w 106 temperature crosses the min or max settings (which by default are set to 75
107 and 80 degrees respectively). 107 and 80 degrees respectively).
108 108
109 Temperature Conversion 109 Temperature Conversion
110 ---------------------- 110 ----------------------
111 111
112 - DS1621 - 750ms (older devices may take up to 112 - DS1621 - 750ms (older devices may take up to 1000ms)
113 - DS1625 - 500ms 113 - DS1625 - 500ms
114 - DS1631 - 93ms..750ms for 9..12 bits resoluti 114 - DS1631 - 93ms..750ms for 9..12 bits resolution, respectively.
115 - DS1721 - 93ms..750ms for 9..12 bits resoluti 115 - DS1721 - 93ms..750ms for 9..12 bits resolution, respectively.
116 - DS1731 - 93ms..750ms for 9..12 bits resoluti 116 - DS1731 - 93ms..750ms for 9..12 bits resolution, respectively.
117 117
118 Note: 118 Note:
119 On the DS1621, internal access to non-volatile 119 On the DS1621, internal access to non-volatile registers may last for 10ms
120 or less (unverified on the other devices). 120 or less (unverified on the other devices).
121 121
122 Temperature Accuracy 122 Temperature Accuracy
123 -------------------- 123 --------------------
124 124
125 - DS1621: +/- 0.5 degree Celsius (from 0 to +7 125 - DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees)
126 - DS1625: +/- 0.5 degree Celsius (from 0 to +7 126 - DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees)
127 - DS1631: +/- 0.5 degree Celsius (from 0 to +7 127 - DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees)
128 - DS1721: +/- 1.0 degree Celsius (from -10 to 128 - DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees)
129 - DS1731: +/- 1.0 degree Celsius (from -10 to 129 - DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees)
130 130
131 .. Note:: 131 .. Note::
132 132
133 Please refer to the device datasheets for a 133 Please refer to the device datasheets for accuracy at other temperatures.
134 134
135 Temperature Resolution: 135 Temperature Resolution:
136 ----------------------- 136 -----------------------
137 As mentioned above, the DS1631, DS1721, and DS 137 As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution
138 support, which is achieved via the R0 and R1 c 138 support, which is achieved via the R0 and R1 config register bits, where:
139 139
140 R0..R1 140 R0..R1
141 ------ 141 ------
142 142
143 == == =============================== 143 == == ===============================
144 R0 R1 144 R0 R1
145 == == =============================== 145 == == ===============================
146 0 0 9 bits, 0.5 degrees Celsius 146 0 0 9 bits, 0.5 degrees Celsius
147 1 0 10 bits, 0.25 degrees Celsius 147 1 0 10 bits, 0.25 degrees Celsius
148 0 1 11 bits, 0.125 degrees Celsius 148 0 1 11 bits, 0.125 degrees Celsius
149 1 1 12 bits, 0.0625 degrees Celsius 149 1 1 12 bits, 0.0625 degrees Celsius
150 == == =============================== 150 == == ===============================
151 151
152 .. Note:: 152 .. Note::
153 153
154 At initial device power-on, the default res 154 At initial device power-on, the default resolution is set to 12-bits.
155 155
156 The resolution mode for the DS1631, DS1721, or 156 The resolution mode for the DS1631, DS1721, or DS1731 can be changed from
157 userspace, via the device 'update_interval' sy 157 userspace, via the device 'update_interval' sysfs attribute. This attribute
158 will normalize the range of input values to th 158 will normalize the range of input values to the device maximum resolution
159 values defined in the datasheet as follows: 159 values defined in the datasheet as follows:
160 160
161 ============= ================== ============= 161 ============= ================== ===============
162 Resolution Conversion Time Input Range 162 Resolution Conversion Time Input Range
163 (C/LSB) (msec) (msec) 163 (C/LSB) (msec) (msec)
164 ============= ================== ============= 164 ============= ================== ===============
165 0.5 93.75 0....94 165 0.5 93.75 0....94
166 0.25 187.5 95...187 166 0.25 187.5 95...187
167 0.125 375 188..375 167 0.125 375 188..375
168 0.0625 750 376..infini 168 0.0625 750 376..infinity
169 ============= ================== ============= 169 ============= ================== ===============
170 170
171 The following examples show how the 'update_in 171 The following examples show how the 'update_interval' attribute can be
172 used to change the conversion time:: 172 used to change the conversion time::
173 173
174 $ cat update_interval 174 $ cat update_interval
175 750 175 750
176 $ cat temp1_input 176 $ cat temp1_input
177 22062 177 22062
178 $ 178 $
179 $ echo 300 > update_interval 179 $ echo 300 > update_interval
180 $ cat update_interval 180 $ cat update_interval
181 375 181 375
182 $ cat temp1_input 182 $ cat temp1_input
183 22125 183 22125
184 $ 184 $
185 $ echo 150 > update_interval 185 $ echo 150 > update_interval
186 $ cat update_interval 186 $ cat update_interval
187 188 187 188
188 $ cat temp1_input 188 $ cat temp1_input
189 22250 189 22250
190 $ 190 $
191 $ echo 1 > update_interval 191 $ echo 1 > update_interval
192 $ cat update_interval 192 $ cat update_interval
193 94 193 94
194 $ cat temp1_input 194 $ cat temp1_input
195 22000 195 22000
196 $ 196 $
197 $ echo 1000 > update_interval 197 $ echo 1000 > update_interval
198 $ cat update_interval 198 $ cat update_interval
199 750 199 750
200 $ cat temp1_input 200 $ cat temp1_input
201 22062 201 22062
202 $ 202 $
203 203
204 As shown, the ds1621 driver automatically adju 204 As shown, the ds1621 driver automatically adjusts the 'update_interval'
205 user input, via a step function. Reading back 205 user input, via a step function. Reading back the 'update_interval' value
206 after a write operation provides the conversio 206 after a write operation provides the conversion time used by the device.
207 207
208 Mathematically, the resolution can be derived 208 Mathematically, the resolution can be derived from the conversion time
209 via the following function: 209 via the following function:
210 210
211 g(x) = 0.5 * [minimum_conversion_time/x] 211 g(x) = 0.5 * [minimum_conversion_time/x]
212 212
213 where: 213 where:
214 214
215 - 'x' = the output from 'update_interval' 215 - 'x' = the output from 'update_interval'
216 - 'g(x)' = the resolution in degrees C per LS 216 - 'g(x)' = the resolution in degrees C per LSB.
217 - 93.75ms = minimum conversion time 217 - 93.75ms = minimum conversion time
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