(sorry for the duplicate, got bounces due to HTML encoding)
The specified patch is already included. The system was running the
latest kernel from Robert Nelson's repo. Any suggestions? I'll try
removing some of the patches to see if it fixes this behavior. I have a
feeling I know which one is doing it.
Thanks.
output from running patch.sh with source pulled from
https://github.com/beagleboard/kernel/tree/3.8
/home/bbuild/comp/kernel/patches/adc/0017-IIO-ADC-ti_adc-Fix-1st-sample-read.patch:
applied
Just in case, I built and installed the kernel and the same behavior
persisted.
root@rbone:/# uname -a
Linux rbone 3.8.13-00737-g7dfad77 #1 SMP Sun Mar 30 22:11:44 EDT 2014
armv7l GNU/Linux
gpio30 is connected to AIN4 using a voltage divider
root@rbone:/# cd /sys/class/gpio/
root@rbone:/sys/class/gpio# echo 30 > export
root@rbone:/sys/class/gpio# echo BB-ADC > /sys/devices/bone_capemgr.9/slots
root@rbone:/sys/class/gpio# cd /sys/devices/ocp.3/helper.11/
root@rbone:/sys/devices/ocp.3/helper.11# echo out >
/sys/class/gpio/gpio30/direction
root@rbone:/sys/devices/ocp.3/helper.11# echo 1 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.11# echo 0 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# grep . AIN[0-3] AIN[5-7]
AIN0:1550
AIN1:1213
AIN2:1485
AIN3:795
AIN5:513
AIN6:744
AIN7:1698
root@rbone:/sys/devices/ocp.3/helper.11# echo 1 >
/sys/class/gpio/gpio30/value
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.11# cat AIN4
1460
On 3/30/2014 9:16 AM, Zubair Lutfullah wrote:
https://github.com/beagleboard/kernel/blob/3.8/patches/adc/0017-IIO-ADC-ti_adc-Fix-1st-sample-read.patch
IIRC, this patch fixes this issue
Can you compile the kernel from the sources and check?
https://github.com/beagleboard/kernel/tree/3.8
Regards
ZubairLK
On Sun, Mar 30, 2014 at 7:04 AM, Rob Mosher <nyt@xxxxxxxxxxxxxxxxxxx
<mailto:nyt@xxxxxxxxxxxxxxxxxxx>> wrote:
Just a note, the same behavior persists with BB-ADC dtb and
reading from in_voltage4_raw
On 3/30/2014 12:30 AM, Rob Mosher wrote:
Hello fine developers,
It seems I've stumbled upon a problem while developing a full
featured Ruby gem for the Beaglebone.
It seems a patch included in the beaglebone kernel causes some
issues while reading analog inputs. Apparently the samples
get backlogged by the number of adc pins in use. I'm not sure
which patch exactly as there are a number that affect adc
buffering and I'm not currently setup for kernel building,
however the below output should detail the problem.
Using the official Debian image.
Linux rbone 3.8.13-bone43 #1 SMP Wed Mar 26 14:21:39 UTC 2014
armv7l GNU/Linux
Distributor ID: Debian
Description: Debian GNU/Linux 7.4 (wheezy)
Release: 7.4
Codename: wheezy
root@rbone:~# echo cape-bone-iio >
/sys/devices/bone_capemgr.9/slots
This is the normal and expected behavior.
1.8v applied to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
0v applied to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
1.8v applied to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
0v applied to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
So far working as intended.... Now reading from the other pins.
root@rbone:/sys/devices/ocp.3/helper.12# grep . AIN[0-3] AIN[5-7]
AIN0:1563
AIN1:1221
AIN2:1487
AIN3:789
AIN5:514
AIN6:743
AIN7:1698
Now applying 1.8v to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
Now applying 0v to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
And another example, showing relation to the number of pins in
use.
1.8v to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# grep . AIN[0-3]
AIN0:1697
AIN1:1298
AIN2:1524
AIN3:816
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
0v to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1460
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
1.8v to AIN4
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
0
root@rbone:/sys/devices/ocp.3/helper.12# cat AIN4
1798
--
Rob Mosher
Senior Network and Software Engineer
Hurricane Electric / AS6939
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