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hwmon: (ds1621) Update documentation
Replace some written information with tables to improve readability and to simplify adding newer devices in the future. Signed-off-by: Robert Coulson <rob.coulson@gmail.com> Signed-off-by: Guenter Roeck <linux@roeck-us.net>
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Robert Coulson
Guenter Roeck
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260f81ffc1
commit
87438c2c54
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@ -73,37 +73,57 @@ any of the limits have ever been met or exceeded since last power-up or
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reset. Be aware: When testing, it showed that the status of Tout can change
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with neither of the alarms set.
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Temperature conversion of the DS1621 takes up to 1000ms; internal access to
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non-volatile registers may last for 10ms or below.
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Since there is no version or vendor identification register, there is
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no unique identification for these devices. Therefore, explicit device
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instantiation is required for correct device identification and functionality
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(one device per address in this address range: 0x48..0x4f).
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The DS1625 is pin compatible and functionally equivalent with the DS1621,
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but the DS1621 is meant to replace it. The DS1631, DS1721, and DS1731 are
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also pin compatible with the DS1621, but provide multi-resolution support.
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also pin compatible with the DS1621 and provide multi-resolution support.
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Since there is no version or vendor identification register, there is
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no unique identification for these devices. Therefore, explicit device
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instantiation is required for correct device identification and functionality.
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Additionally, the DS1721 data sheet says the temperature flags (THF and TLF)
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are used internally, however, these flags do get set and cleared as the actual
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temperature crosses the min or max settings (which by default are set to 75
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and 80 degrees respectively).
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And, for correct identification and operation, each device must be
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explicitly instantiated, one device per address, in this address
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range: 0x48..0x4f.
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Temperature Conversion:
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-----------------------
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DS1621 - 750ms (older devices may take up to 1000ms)
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DS1625 - 500ms
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DS1631 - 93ms..750ms for 9..12 bits resolution, respectively.
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DS1721 - 93ms..750ms for 9..12 bits resolution, respectively.
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DS1731 - 93ms..750ms for 9..12 bits resolution, respectively.
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The DS1721 is pin compatible with the DS1621, has an accuracy of +/- 1.0
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degree Celsius (from -10 to +85 degrees), a minimum/maximum alarm default
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setting of 75 and 80 degrees, and a maximum conversion time of 750ms.
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Note:
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On the DS1621, internal access to non-volatile registers may last for 10ms
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or less (unverified on the other devices).
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In addition, the DS1721 supports four resolution settings from 9 to 12 bits
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(defined in degrees C per LSB: 0.5, 0.25, 0.125, and 0.0625, respectively),
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that are set at device power on to the highest resolution: 12-bits.
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Temperature Accuracy:
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---------------------
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DS1621: +/- 0.5 degree Celsius (from 0 to +70 degrees)
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DS1625: +/- 0.5 degree Celsius (from 0 to +70 degrees)
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DS1631: +/- 0.5 degree Celsius (from 0 to +70 degrees)
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DS1721: +/- 1.0 degree Celsius (from -10 to +85 degrees)
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DS1731: +/- 1.0 degree Celsius (from -10 to +85 degrees)
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One additional note about the ds1721 is that although the data sheet says
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the temperature flags (THF and TLF) are used internally, these flags do
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get set and cleared as the actual temperature crosses the min or max settings.
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Note:
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Please refer to the device datasheets for accuracy at other temperatures.
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The DS1631 and DS1731 are pin compatible with the DS1621 and feature compatible
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with the DS1721. However, the DS1631 accuracy is +/- 0.5 degree Celsius (from 0
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to +70 degrees), while the DS1731 accuracy is +/-1 degree Celsius (from -10 to
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+85 degrees).
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Temperature Resolution:
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-----------------------
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As mentioned above, the DS1631, DS1721, and DS1731 provide multi-resolution
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support, which is achieved via the R0 and R1 config register bits, where:
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R0..R1
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------
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0 0 => 9 bits, 0.5 degrees Celcius
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1 0 => 10 bits, 0.25 degrees Celcius
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0 1 => 11 bits, 0.125 degrees Celcius
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1 1 => 12 bits, 0.0625 degrees Celcius
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Note:
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At initial device power-on, the default resolution is set to 12-bits.
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The resolution mode for the DS1631, DS1721, or DS1731 can be changed from
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userspace, via the device 'update_interval' sysfs attribute. This attribute
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@ -112,12 +132,12 @@ values defined in the datasheet as follows:
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Resolution Conversion Time Input Range
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(C/LSB) (msec) (msec)
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--------------------------------------------
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------------------------------------------------
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0.5 93.75 0....94
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0.25 187.5 95...187
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0.125 375 188..375
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0.0625 750 376..infinity
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--------------------------------------
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------------------------------------------------
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The following examples show how the 'update_interval' attribute can be
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used to change the conversion time:
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