/*
* Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
/dts-v1/;
/plugin/;
/ {
compatible = "ti,beaglebone", "ti,beaglebone-black",
"ti,beaglebone-green";
/* identification */
part-number = "BB-ADC";
version = "00A0";
/* state the resources this cape uses */
exclusive-use =
/* the pin header uses */
"P9.31", /* AIN0 */
"P9.40", /* AIN1 */
"P9.37", /* AIN2 */
"P9.38", /* AIN3 */
"P9.33", /* AIN4 */
"P9.36", /* AIN5 */
"P9.35", /* AIN6 */
/* the hardware ip uses */
"tscadc";
fragment@0 {
target = <&tscadc>;
__overlay__ {
status = "okay";
adc {
ti,adc-channels = <0 1 2 3 4 5 6>;
ti,chan-step-avg = <0x16 0x16 0x16 0x16 0x16
0x16 0x16>;
ti,chan-step-opendelay = <0x98 0x98 0x98 0x98
0x98 0x98 0x98>;
ti,chan-step-sampledelay = <0x0 0x0 0x0 0x0 0x0
0x0 0x0>;
};
};
};
};
Reading from /sys/bus/iio/devices/iio:device0/in_voltage0_raw is reading and
attribute of the IIO driver. Reading from /dev/iio:device0 is reading from the
same IIO driver, but in this case you are reading from the buffer which stores
samples defined in the DT overlay above.
Regards,
John
> On Mar 8, 2016, at 9:51 PM, Audrey <[email protected]> wrote:
>
> Thanks for the reply John. Could you perhaps explain how to modify the
> oversample, open delay time, and sample time in greater detail in the BB-ADC
> overlay? I do not see these variables in the dto in github
> (https://github.com/beagleboard/devicetree-source/blob/master/arch/arm/boot/dts/BB-ADC-00A0.dts
>
> <https://github.com/beagleboard/devicetree-source/blob/master/arch/arm/boot/dts/BB-ADC-00A0.dts>).
> Also, what value can/should I change them to?
>
> So just to clarify, reading from
> /sys/bus/iio/devices/iio:device0/in_voltage0_raw reads attributes using
> sysfs, while reading from /dev/iio:device0 reads the values using IIO? Also
> another conceptual question, can you explain what exactly is in_voltage0_raw
> and iio:device0? I know it's not a folder, and I interact with it by using
> cat. So is it just like a text file or something?
>
> Thanks.
>
> On Sunday, March 6, 2016 at 2:15:17 PM UTC-5, john3909 wrote:
> That is because you are doing this wrong. Reading attributes via sysfs is
> slow and not meant for this purpose. With IIO, you enable a scan element
> (echo 1 > in_voltage0_en) and then you enable the buffer (echo 1 >
> buffer/enable)and then you read the values from /dev/iio:device0. In the
> BB-ADC overlay, you can modify the scan update time by modifying the
> Oversample (default is 16x), Open Delay time (default is 0x98) and sample
> time (default is 1). Now the IIO ADC driver captures samples using interrupts
> which isn’t ideal, but it will capture samples at a much higher rate than can
> be read from sysfs. If you want to capture at full speed, the driver needs to
> be updated to use DMA.
>
> Regards,
> John
>
>
>
>
>> On Mar 6, 2016, at 12:19 AM, Audrey <ao...@ <>smith.edu <http://smith.edu/>>
>> wrote:
>>
>> Where can I find it (and set it)?
>>
>> I'm right now trying to collect voltage readings using beaglebone's internal
>> adc using a bash script and a while loop. Right now the data collection is
>> clocking at around 33 microseconds, but I know that the internal adc should
>> be able to collect data as fast as 5 microseconds. What should I do to make
>> that happen? Is the problem with making while loops move faster, or is it
>> about setting the adc configurations?
>>
>> This is my bash script:
>>
>> #!/bin/bash
>>
>> #echo cape-bone-iio > /sys/devices/bone_capemgr.*/slots
>>
>> t0=$(date +%s%6N)
>>
>> while true; do
>> t1=$(date +%s%6N)
>> rawVal=$(cat /sys/bus/iio/devices/iio:device0/in_voltage0_raw)
>> voltage=$(bc -l <<< $rawVal/4095*1.8)
>> time=$(expr $t1 - $t0)
>> echo $time $voltage
>> done
>>
>>
>> --
>> For more options, visit http://beagleboard.org/discuss
>> <http://beagleboard.org/discuss>
>> ---
>> You received this message because you are subscribed to the Google Groups
>> "BeagleBoard" group.
>> To unsubscribe from this group and stop receiving emails from it, send an
>> email to beagleboard...@ <>googlegroups.com <http://googlegroups.com/>.
>> For more options, visit https://groups.google.com/d/optout
>> <https://groups.google.com/d/optout>.
>
>
> --
> For more options, visit http://beagleboard.org/discuss
> <http://beagleboard.org/discuss>
> ---
> You received this message because you are subscribed to the Google Groups
> "BeagleBoard" group.
> To unsubscribe from this group and stop receiving emails from it, send an
> email to [email protected]
> <mailto:[email protected]>.
> For more options, visit https://groups.google.com/d/optout
> <https://groups.google.com/d/optout>.
--
For more options, visit http://beagleboard.org/discuss
---
You received this message because you are subscribed to the Google Groups
"BeagleBoard" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
