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diff --git a/Documentation/i2c/chips/ds1621 b/Documentation/i2c/chips/ds1621 deleted file mode 100644 index 1fee6f1..0000000 --- a/Documentation/i2c/chips/ds1621 +++ /dev/null @@ -1,108 +0,0 @@ -Kernel driver ds1621 -==================== - -Supported chips: - * Dallas Semiconductor DS1621 - Prefix: 'ds1621' - Addresses scanned: I2C 0x48 - 0x4f - Datasheet: Publicly available at the Dallas Semiconductor website - http://www.dalsemi.com/ - * Dallas Semiconductor DS1625 - Prefix: 'ds1621' - Addresses scanned: I2C 0x48 - 0x4f - Datasheet: Publicly available at the Dallas Semiconductor website - http://www.dalsemi.com/ - -Authors: - Christian W. Zuckschwerdt <zany@triq.net> - valuable contributions by Jan M. Sendler <sendler@sendler.de> - ported to 2.6 by Aurelien Jarno <aurelien@aurel32.net> - with the help of Jean Delvare <khali@linux-fr.org> - -Module Parameters ------------------- - -* polarity int - Output's polarity: 0 = active high, 1 = active low - -Description ------------ - -The DS1621 is a (one instance) digital thermometer and thermostat. It has -both high and low temperature limits which can be user defined (i.e. -programmed into non-volatile on-chip registers). Temperature range is -55 -degree Celsius to +125 in 0.5 increments. You may convert this into a -Fahrenheit range of -67 to +257 degrees with 0.9 steps. If polarity -parameter is not provided, original value is used. - -As for the thermostat, behavior can also be programmed using the polarity -toggle. On the one hand ("heater"), the thermostat output of the chip, -Tout, will trigger when the low limit temperature is met or underrun and -stays high until the high limit is met or exceeded. On the other hand -("cooler"), vice versa. That way "heater" equals "active low", whereas -"conditioner" equals "active high". Please note that the DS1621 data sheet -is somewhat misleading in this point since setting the polarity bit does -not simply invert Tout. - -A second thing is that, during extensive testing, Tout showed a tolerance -of up to +/- 0.5 degrees even when compared against precise temperature -readings. Be sure to have a high vs. low temperature limit gap of al least -1.0 degree Celsius to avoid Tout "bouncing", though! - -As for alarms, you can read the alarm status of the DS1621 via the 'alarms' -/sys file interface. The result consists mainly of bit 6 and 5 of the -configuration register of the chip; bit 6 (0x40 or 64) is the high alarm -bit and bit 5 (0x20 or 32) the low one. These bits are set when the high or -low limits are met or exceeded and are reset by the module as soon as the -respective temperature ranges are left. - -The alarm registers are in no way suitable to find out about the actual -status of Tout. They will only tell you about its history, whether or not -any of the limits have ever been met or exceeded since last power-up or -reset. Be aware: When testing, it showed that the status of Tout can change -with neither of the alarms set. - -Temperature conversion of the DS1621 takes up to 1000ms; internal access to -non-volatile registers may last for 10ms or below. - -High Accuracy Temperature Reading ---------------------------------- - -As said before, the temperature issued via the 9-bit i2c-bus data is -somewhat arbitrary. Internally, the temperature conversion is of a -different kind that is explained (not so...) well in the DS1621 data sheet. -To cut the long story short: Inside the DS1621 there are two oscillators, -both of them biassed by a temperature coefficient. - -Higher resolution of the temperature reading can be achieved using the -internal projection, which means taking account of REG_COUNT and REG_SLOPE -(the driver manages them): - -Taken from Dallas Semiconductors App Note 068: 'Increasing Temperature -Resolution on the DS1620' and App Note 105: 'High Resolution Temperature -Measurement with Dallas Direct-to-Digital Temperature Sensors' - -- Read the 9-bit temperature and strip the LSB (Truncate the .5 degs) -- The resulting value is TEMP_READ. -- Then, read REG_COUNT. -- And then, REG_SLOPE. - - TEMP = TEMP_READ - 0.25 + ((REG_SLOPE - REG_COUNT) / REG_SLOPE) - -Note that this is what the DONE bit in the DS1621 configuration register is -good for: Internally, one temperature conversion takes up to 1000ms. Before -that conversion is complete you will not be able to read valid things out -of REG_COUNT and REG_SLOPE. The DONE bit, as you may have guessed by now, -tells you whether the conversion is complete ("done", in plain English) and -thus, whether the values you read are good or not. - -The DS1621 has two modes of operation: "Continuous" conversion, which can -be understood as the default stand-alone mode where the chip gets the -temperature and controls external devices via its Tout pin or tells other -i2c's about it if they care. The other mode is called "1SHOT", that means -that it only figures out about the temperature when it is explicitly told -to do so; this can be seen as power saving mode. - -Now if you want to read REG_COUNT and REG_SLOPE, you have to either stop -the continuous conversions until the contents of these registers are valid, -or, in 1SHOT mode, you have to have one conversion made. |