Hi Khali,
On Mon, 9 May 2005 15:35:36 +0200 (CEST), "Jean Delvare" <khali at linux-fr.org> wrote:
>Your code makes sense for external resistors, but not for internal
>scaling as far as I can see, so it won't be of any help in the drivers.
>And libsensors mostly works the way you describe already, just not in as
>formal a way (because compute lines were meant for all values, not just
>voltages).
>So all in all I think that you are trying to fix a problem that doesn't
>exist in the first place, sorry.
Just reviewed /etc/sensors.conf again, negative voltage calculation
is totally bogus as it does not account for reference voltage driving
top of resistor divider. The proof is that you do not have correct
Winbond resistor values in the sample calculations. They're fudged.
+12V: compute in4 ((28/10)+1)*@ , @/((28/10)+1) uses Winbond values
Fudged negative calculations:
-12V: compute in5 -(210/60.4)*@ , -@/(210/60.4) 210/60.4 = 3.47
versus datasheet: 232/56 = 4.14
-5V: compute in6 -(90.9/60.4)*@ , -@/(90.9/60.4) 90.9/60.4 = 1.5
versus datasheet: 120/56 = 2.14
Parameter based calculation does not have these issues, doesn't
need floating point either. I think this is the background thing
bugging me for weeks since I looked at sensors.conf
What do you need for further proof? My interest is correctness.
Numbers traceable to datasheet is easy way. My last reply
detailed calibration to mobo use of other than sensor chip
suggested values.
Another section of my shell script (fixed point math):
Vref=3600 # mV reference driving top of Vminus voltage divider
function scale_voltage # nr, scale type: none, plus, minus
{
local r1=${R1spec[${1}]}
local r2=${R2spec[${1}]}
local in=${Vread[${1}]}
case $2 in
0 ) Vshow[${1}]=$in;;
1 ) Vshow[${1}]=$(((in * (r1 + r2) + r1 / 2) / r1));;
2 ) Vshow[${1}]=$(((((in - Vref) * r2 + r1 / 2) / r1) + in));;
* ) Vshow[${1}]=0;;
esac
}
--Grant.
