Look at AM3358 TRM Figure 12-3 on Page 1497 Regards, John
> On Mar 9, 2016, at 1:04 AM, William Hermans <[email protected]> wrote: > > John, also Audry asked what the values of that device tree fragment mean, not > what the code was. As in Audry wants and explanation of the values: > > 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>; > > As far as I can tell. Quite honestly I could use that explanation myself. But > step avg can be a value 0-16 if memory serves from reading the TRM, I'm just > not clear exactly on what step avg actually does. . . . the explanation in > the TRM is very jumbled / confusing. > > > On Wed, Mar 9, 2016 at 1:58 AM, William Hermans <[email protected] > <mailto:[email protected]>> wrote: > 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 > <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 <[email protected] > <mailto:[email protected]>> 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 <[email protected] > <mailto:[email protected]>> wrote: > /* > * Copyright (C) 2012 Texas Instruments Incorporated - http://www.ti.com/ > <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] <mailto:[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 > <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 > <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. 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