[meta-xilinx] JTAG versus OS - XADC differences in temperature

Giordon Stark kratsg at gmail.com
Fri Mar 24 11:40:12 PDT 2017


I'm not sure if anyone's seen this before or if I'm doing something wrong.
http://i.imgur.com/KPRvx42.png - here's a screenshot of what I'm seeing
through the Hardware Manager for a Zynq-7000 (7020 evaluation) board. In
the OS, I combine the numbers from three memory-mapped files to calculate
the temperature of the board.

On average, i'm seeing ~42C from the OS via command line, while I'm seeing
~47C over JTAG in the hardware manager. Is there a known discrepancy? Which
do I trust more?

Command I run:

$ cat /sys/devices/soc0/amba at 0/f8007100.ps7-xadc/iio\:device0/in_temp0_* |
tr '\n' '\t' | awk '{print ($1 + $2)*$3}'

Note that

$ cat /sys/devices/soc0/amba at 0/f8007100.ps7-xadc/iio\:device0/in_temp0_*

produces an output like


So it just looks like I'm meant to add the first two, and multiply by the
3rd -- and this gives me a number in milliCelsius.

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