mirror of
https://github.com/lm-sensors/lm-sensors.git
synced 2026-10-19 11:19:31 +00:00
Jean Delvare
2f070b1860
porting the chips documentation to Linux 2.6. git-svn-id: http://lm-sensors.org/svn/lm-sensors/trunk@3007 7894878c-1315-0410-8ee3-d5d059ff63e0
238 lines
10 KiB
Plaintext
238 lines
10 KiB
Plaintext
Kernel driver `ds1621.o'
|
|
========================
|
|
|
|
Status: Complete and tested; enhanced features experimental
|
|
|
|
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/
|
|
|
|
Author: Christian W. Zuckschwerdt <zany@triq.net>
|
|
valueable contributions by Jan M. Sendler <sendler@sendler.de>
|
|
|
|
|
|
Module Parameters
|
|
-----------------
|
|
|
|
* force: short array (min = 1, max = 48)
|
|
List of adapter,address pairs to boldly assume to be present
|
|
* force_ds1621: short array (min = 1, max = 48)
|
|
List of adapter,address pairs which are unquestionably assumed to
|
|
contain a `ds1621' chip
|
|
* ignore: short array (min = 1, max = 48)
|
|
List of adapter,address pairs not to scan
|
|
* ignore_range: short array (min = 1, max = 48)
|
|
List of adapter,start-addr,end-addr triples not to scan
|
|
* probe: short array (min = 1, max = 48)
|
|
List of adapter,address pairs to scan additionally
|
|
* probe_range: short array (min = 1, max = 48)
|
|
List of adapter,start-addr,end-addr triples to scan additionally
|
|
|
|
|
|
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. Unfortunally though, you will need a hash table or even a
|
|
conversion routine for that.
|
|
|
|
Temperature readings are internally converted into a 9bit value to be
|
|
read straight via the i2c-bus, but higher resolutions may be obtained
|
|
with little effort via 'precise_temp' access or using a simple algorithm.
|
|
|
|
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' proc file interface. The result consits 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.
|
|
|
|
This driver also detects DS1625. As this chip is discontinued, you
|
|
should use a DS1621 instead. Detected 1625s also get the
|
|
"ds1621"-prefix, but the accuracy registers are not supported.
|
|
The latest modification of this driver was not checked against 1625s,
|
|
though, but should work well with them.
|
|
|
|
Default values written into the DS1621 upon detection are:
|
|
Temperature limits: High 60.0; low 0.0 degree Celsius;
|
|
Continuous mode (not enabled), Tout active high, alarms reset.
|
|
|
|
|
|
Accessing DS1621 via /proc interface (part I)
|
|
---------------------------------------------
|
|
|
|
On detection (i.e. insmod, modprobe et al.), directories are being
|
|
created for each detected DS1621:
|
|
|
|
/proc/sys/dev/sensors/ds1621-<0>-<1>/
|
|
where <0> is the bus the chip was detected on (e. g. i2c-0)
|
|
and <1> the chip address ([48..4f]): ./ds1621-i2c-0-48/
|
|
|
|
Inside these directories, there are five files each:
|
|
alarms, continuous, enable, polarity and temp.
|
|
|
|
The temp, alarms and enable are LM75-like for compatibility reasons:
|
|
|
|
The temp file is rw. Reading gives TEMP_HIGH:TEMP_HYST:TEMP, where
|
|
TEMP_HIGH is the upper limit temp, TEMP_HYST is the hysteresis (lower
|
|
limit) temp and TEMP is the actual temperature. (For things like
|
|
ONE_SHOT, see below.) - Writing takes two results (read: input
|
|
values): TEMP_HIGH:TEMP_HYST. This provides an easy way to set limits.
|
|
|
|
The alarms file is ro. Basically, it is 0x40 ("64") for the high alarm
|
|
bit set plus 0x20 ("32") for the low one. Since alarms are being reset
|
|
by the module when the limit conditions are no longer met, you should
|
|
first read the alarms before you do anything else (such as reading the
|
|
temperature), or the information may be lost.
|
|
|
|
The polarity file is rw. Reading gives "0" for active high, which
|
|
describes a need for cooling corresponds to Tout status. "1" means
|
|
active low, so you can connect a powerful heater directly to Tout
|
|
(DON'T TRY!). - Writing accepts "0" and "1" accordingly. Again, note
|
|
that the statements on page 5 of the DS1621 data sheet are misleading;
|
|
change the orientation of the vertical arrows in the sketch there
|
|
instead.
|
|
|
|
To understand the use of the other things, it is useful to have a
|
|
brief look at the internal DS1621 procedures:
|
|
|
|
|
|
High Accuracy Temperature Reading
|
|
---------------------------------
|
|
|
|
As said before, the temperature issued via the 9bit 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 accuracy 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 9bit 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.
|
|
|
|
|
|
|
|
Accessing DS1621 via /proc interface (part II and end)
|
|
------------------------------------------------------
|
|
|
|
The continuous file is rw. Reading gives "1" when the chip is in
|
|
continuous mode and "0" for 1SHOT. - Writing accepts "1" to put it
|
|
into continuous mode or "0" for 1SHOT.
|
|
|
|
The enable file is rw. Reading gives "1" if in continuous mode the
|
|
DS1621 is "running" or if in 1SHOT mode it is "shooting". In fact, the
|
|
value returned here is the negated DONE bit, just like a "BUSY"
|
|
flag. This means, that the "1" tells you that the values in REG_COUNT
|
|
and REG_SLOPE are not valid. "0", on the other hand, means that the
|
|
continuous conversion had been stopped long enough to provide valid
|
|
readings and that one shot has successfully been fi- red,
|
|
respectively. - Writing accepts "1" to start continuous conversion or
|
|
to pull the trigger in 1SHOT mode, and "0" stops continuous conversion
|
|
to allow for valid readings. Writing "0" in 1SHOT doesn't make much
|
|
sense since you cannot catch a bullet, can you? No, the thing is that
|
|
DS1621 does only do one conversion then anyway, and after that,
|
|
there's nothing to stop.
|
|
|
|
Last, but best try writing "0" to the "continuous" file and after that
|
|
"1" to the "enable" file. This gives you the precise temperature with
|
|
two digits after the radix (decimal point).
|
|
The precise results are only updated if the DONE bit was set, thus you
|
|
have to stop continuous conversion early enough prior to reading,
|
|
i. e. 1000ms. And, on the other hand, you shouldn't forget to fire off
|
|
1SHOT in order to get the actual temperature rather than that of the
|
|
day before yesterday. So read enable before any of these.
|
|
|
|
|
|
Chip Features
|
|
-------------
|
|
|
|
Chip `ds1621'
|
|
LABEL LABEL CLASS COMPUTE CLASS ACCESS MAGNITUDE
|
|
temp NONE NONE R 1
|
|
temp_hyst temp temp RW 1
|
|
temp_over temp temp RW 1
|
|
alarms NONE NONE R 0
|
|
enable NONE NONE RW 0
|
|
continuous NONE NONE RW 0
|
|
polarity NONE NONE RW 0
|
|
|
|
LABEL FEATURE SYMBOL SYSCTL FILE:OFFSET
|
|
temp SENSORS_DS1621_TEMP temp:3
|
|
temp_hyst SENSORS_DS1621_TEMP_HYST temp:2
|
|
temp_over SENSORS_DS1621_TEMP_OVER temp:1
|
|
alarms SENSORS_DS1621_ALARMS alarms:1
|
|
enable SENSORS_DS1621_ENABLE enable:1
|
|
continuous SENSORS_DS1621_CONTINUOUS continuous:1
|
|
polarity SENSORS_DS1621_POLARITY polarity:1
|