Based on kernel version 4.16.1. Page generated on 2018-04-09 11:53 EST.
1 Kernel driver ds1621 2 ==================== 3 4 Supported chips: 5 * Dallas Semiconductor / Maxim Integrated DS1621 6 Prefix: 'ds1621' 7 Addresses scanned: none 8 Datasheet: Publicly available from www.maximintegrated.com 9 10 * Dallas Semiconductor DS1625 11 Prefix: 'ds1625' 12 Addresses scanned: none 13 Datasheet: Publicly available from www.datasheetarchive.com 14 15 * Maxim Integrated DS1631 16 Prefix: 'ds1631' 17 Addresses scanned: none 18 Datasheet: Publicly available from www.maximintegrated.com 19 20 * Maxim Integrated DS1721 21 Prefix: 'ds1721' 22 Addresses scanned: none 23 Datasheet: Publicly available from www.maximintegrated.com 24 25 * Maxim Integrated DS1731 26 Prefix: 'ds1731' 27 Addresses scanned: none 28 Datasheet: Publicly available from www.maximintegrated.com 29 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> 34 with the help of Jean Delvare <jdelvare@suse.de> 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 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. 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 76 Since there is no version or vendor identification register, there is 77 no unique identification for these devices. Therefore, explicit device 78 instantiation is required for correct device identification and functionality 79 (one device per address in this address range: 0x48..0x4f). 80 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 Celsius 121 1 0 => 10 bits, 0.25 degrees Celsius 122 0 1 => 11 bits, 0.125 degrees Celsius 123 1 1 => 12 bits, 0.0625 degrees Celsius 124 125 Note: 126 At initial device power-on, the default resolution is set to 12-bits. 127 128 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: 132 133 Resolution Conversion Time Input Range 134 (C/LSB) (msec) (msec) 135 ------------------------------------------------ 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 140 ------------------------------------------------ 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