Now if you want to convey more information that is actually *useful* to anyone reading this post. You can say that both voltageX_raw, and iio:deviceX are buffers.
With voltageX_raw being a single value buffer that gets updated only once every open() call on it's file descriptor. Where iio:deviceX is a buffer, defined in size by the value set in /sys/bus/iio/devices/iio\:device0/buffer/length More *useful* information can be found here: http://processors.wiki.ti.com/index.php/AM335x_ADC_Driver's_Guide. Then if you want even more information still, googling "iio" will produce a lot of information. Much of it not so useful. At least for our use case, the Beaglebone. On Wed, Mar 9, 2016 at 1:47 AM, William Hermans <yyrk...@gmail.com> wrote: > what the hell does what you've said there even mean John ? voltagex_raw is > one shot mode, iio:deviceX is continuous mode. > > What you said above only serves to confuse the situation. > > On Wed, Mar 9, 2016 at 1:32 AM, John Syne <john3...@gmail.com> wrote: > >> /* >> * 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 <a...@smith.edu> 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). >> 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> 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 >>> --- >>> 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. >>> For more options, visit 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 beagleboard+unsubscr...@googlegroups.com. >> For more options, visit 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 beagleboard+unsubscr...@googlegroups.com. >> For more options, visit 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. 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