On 12/10/2015 09:12 AM, Andreas Werner wrote:
On Thu, Dec 10, 2015 at 08:41:57AM -0800, Guenter Roeck wrote:
On 12/10/2015 04:08 AM, Andreas Werner wrote:
Hi,
i have a temperature sensor device named "TI TMP461" which is quite the
same than the tmp451 which is already included in the lm90 driver.
I just want to add the tmp461 to the driver but currently i have no way
to differ between the tmp461 and tmp451.
The main different is that the tmp461 address can be configured by to Pins
whereas the tmp451 has a fixed address.
The register layout is quite the same except that the tmp461 has one
register more (0x16 Channel Enable Register).
Every zero bit is the same for both bits, so we cannot use these bits for
identification.
Does anybody of you have a tmp451 to read out the register 0x16 (which is
not implement but i expect a value). May be we can use this to
identify the tmp461.
Here is a register dump.
00: 5d 69 00 04 08 bf 00 ff 53 00 00 00 00 00 00 00 ]i.???..S.......
10: a0 00 00 00 00 f0 00 00 00 a9 00 00 00 00 00 00 ?....?...?......
20: b8 0a 01 00 00 XX 00 00 00 00 0e 00 00 00 00 00 ???..X....?.....
30: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
40: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
50: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
60: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
70: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
d0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................
f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 55 00 ..............U.
there is nothing to distinguish the two chips as far as I can see.
Is your system a devicetree system ? If so, you can just
provide a compatible statement such as
compatible = "ti,tmp461", "ti,tmp451";
or simply instantiate the chip as tmp451.
Feel free to provide a patch adding '{ "tmp461", tmp451 },'
to lm90_id as well as the necessary documentation, but I don't
think there is anything we can do to detect the chip.
On the other side, I am a bit concerned that the chip detection doesn't
work well, since the chip ID register is really unsupported and just happens
to return 0 for both chips. I wonder if there are other TI chips which may
be mis-detected as TMP451.
Thanks,
Guenter
Hi,
thanks for the register dump :-)
There is one difference. The temperature ranges differ:
TMP451:
Standard Mode: 0 to +127
Extended Mode: -64 to +191
TMP461:
Standard Mode: -40 to +127
Extended Mode: -64 to +191
Therefore the calcualtion is different then the tmp451 one.
Not really. The tmp451 will return 0 for negative temperatures in standard mode,
the tmp461 will return negative (signed) values. Temperatures are stored
as signed values, so the code should be ok as is. Am I missing something ?
I also aggree with you with the magical ID register. I hate such
kind of register with are not documented and may have a value.
I have a DT based board yes, but i have also planed to submit my changes
and also wanted to implement the autodetection of the chip.
I don't think auto-detection (other than handling the chip as tmp451)
will be possible, but I am looking forward to seeing your patch(es).
I have also planned (or need) to implement the "n-Factor Correction" for the
CPU diodes. There is a register to set this value in the tmp451 and tmp461.
Would that make sense to add a DT property for the driver to be able
to set this value? What do you think?
Yes, since this is a board (hardware) property. Other chips have similar
registers. We'll just have to find a good set of property names and
descriptions.
Thanks,
Guenter
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