BTW, you can run iiod on your BBB and then use IIO Oscilloscope on you desktop which can connect to your BBB and display the waveforms.
https://wiki.analog.com/resources/tools-software/linux-software/iio_oscilloscope <https://wiki.analog.com/resources/tools-software/linux-software/iio_oscilloscope> Regards, John > On May 18, 2018, at 4:57 PM, pierrick.ra...@gadz.org wrote: > > > John, > I am still working on this project. I have studied the iio_generic_buffer.c > and adapted it to save the result of the sampling in a csv file. I was > testing it today with a waveform generator in the following configuration: > - signal frequency : 1Hz (sin function) > - signal amplitude: 1V > - averaging 8 times > > I took 1000 samples (buffer length 1000), I then displayed the result and > instead of a constant horizontal line, i had a sinus-like curve (attached as > 8 average sin 1Hz 1000 samples). > > I tried with higher frequencies such as 20khz and i have a similar result but > with a "pulse" which, as far as understand corresponds to the signal I want > to sample ( attached as 8 average sin20kHz). > > In both cases, I have some "waves" that does not seems to be linked to the > frequency of the signal... > > I guess something is wrong in my iio_generic_buffer.c like i am not reading > the data at the right place... but i do not really know what kind of error I > should look for, I am also attaching it to this post (maybe it can help). > The changes I made are from the patch on this page : > https://www.teachmemicro.com/beaglebone-black-adc/ and I also modified the > process_scan(), print2byte() function and the main (~line 650) to save the > value in a csv file instead of just printing them. > > If you can give me an hint of where my error could be it would be very > helpful. > > Thanks a lot, > > Pierrick > > > Le mardi 17 avril 2018 00:19:16 UTC-4, john3909 a écrit : > > > >> On Apr 16, 2018, at 3:40 PM, pierric...@gadz.org <> wrote: >> >> Hi John, >> Thanks a lot for this very complete answer ! I think I understand it now, >> the last point I am not sure about is: >> >> ti,chan-step-avg = <1 1 1 1 1 1 1 1> /* 2 sample average */ >> >> I went through 12.3.3 of the AM3358 Technical Reference Manual and it seems >> that the setting the averaging value to 1 disable the averaging (instead of >> setting it to 2) am I right? >> Thanks again for your help > If you look in the AM3358 TRM, it says 0 will disable averaging and 1 will > average over two samples. > > From the TRM > > Number of samplings to average: > 000 = No average. > 001 = 2 samples average. > 010 = 4 samples average. > 011 = 8 samples average. > 100 = 16 samples average. > > Regards, > John >> >> Le mercredi 11 avril 2018 17:00:54 UTC-4, john3909 a écrit : >> >> >>> On Apr 11, 2018, at 6:04 AM, pierric...@gadz.org <> wrote: >>> >>> Hi John, >>> Thanks for the help, I looked into the iio_generic_buffer.c example and i >>> patched it to disable the hardware triggers thanks to the patch presented >>> on this page : https://www.teachmemicro.com/beaglebone-black-adc/ >>> <https://www.teachmemicro.com/beaglebone-black-adc/> I am now able to >>> reader a buffer from the different channel. >>> However I have 2 majors questions that remains: >>> >>> 1) I only want to use on channel, then I do not want the ADC to sample the >>> other one so that i'll have the maximum sampling rate. What is the best way >>> to disable the channel? If I do not enable them in iio_generic_buffer.c I >>> am not sure that the ADC is not going to sample this channel or not (well, >>> I think it wont sample but I prefer to be sure). Is it preferable to not >>> mention them on the devicetree so that Linux wont know that there are >>> multiple channels on the ADC? This part is not very clear for me. >>> >>> 2) To change the sample frequency of the ADC you mentioned that it is done >>> using the device tree however I did not find any argument on the ADC >>> devicetree to change the sampling frequency. I read the discussion you had >>> on this post (https://patchwork.kernel.org/patch/9391487/ >>> <https://patchwork.kernel.org/patch/9391487/> ) but it is not clear if the >>> frequency setting is done using the kernel module or devicetrees. Could you >>> explain me this please? >> Looking at this a little more, there is a mistake in the ADC DT file >> BB-ADC-0A00.dts. The maximum averaging is 16, not 0x16. >> >> The line >> ti,chan-step-avg = <0x16 0x16 0x16 0x16 0x16 0x16 0x16 0x16> >> >> should be changed to >> ti,chan-step-avg = <16 16 16 16 16 16 16 16> >> Fortunately, the driver does a range check and sets the value to 16. >> >> ti,chan-step-avg = <1 1 1 1 1 1 1 1> /* 2 sample average */ >> ti,chan-step-opendelay = <0 0 0 0 0 0 0 0> >> ti,chan-step-sampledelay = <0 0 0 0 0 0 0 0> >> >> To achieve a conversion rate of 800 KS/s >> >> From ti_am335x_tscad.c, 1 + (1 + 13) * 2 = 30 cycles >> >> The ADC uses a 24 MHz clock, so 1/24,000,000 * 15 = 800 KS/s >> >> You could increase the sampling rate to 1.6MS/s by changing the average to >> 0, which means there is no averaging. To achieve this, the minimum number of >> cycles for a conversion is 15 (12.3.7 of the AM3358 Technical Reference >> Manual) >> >> 1 + (1 + 13) * 1 = 15 cycles >> >> which will give you 1.6 MS/s >> >> Regards, >> John >> >>> >>> Thanks a lot >>> >>> Pierrick >>> >>> Le mercredi 28 mars 2018 00:45:01 UTC-4, john3909 a écrit : >>> Look at the kernel source under tools/iio for examples on how to use IIO. >>> >>> Regards, >>> John >>> >>> >>> >>> >>> >>>> On Mar 27, 2018, at 12:10 PM, pierric...@gadz.org <> wrote: >>>> >>>> Hi John, >>>> >>>> Sorry for the late answer, I had hard time using the PRUs and I am now >>>> going to use the IIO ADC driver, I am able to read the sample with the cat >>>> command in /sys/bus/iio/devices/iio:device0/in_voltage3_raw >>>> However I am not able to use Libiio in order to read data from a user >>>> space application, I am reading (nil) instead of my data. Do you have any >>>> idea of where does the problem comes from ? >>>> >>>> Here is the code I am using in the user space : >>>> >>>> >>>> #define _BSD_SOURCE >>>> #define _GNU_SOURCE >>>> #define _DEFAULT_SOURCE >>>> >>>> #include <cdk/cdk.h> >>>> #include <locale.h> >>>> #include <pthread.h> >>>> #include <stdbool.h> >>>> #include <unistd.h> >>>> #include <stdint.h> >>>> #include <stdio.h> >>>> #include <string.h> >>>> >>>> #ifdef __APPLE__ >>>> #include <iio/iio.h> >>>> #else >>>> #include <iio.h> >>>> #endif >>>> >>>> struct iio_context *ctx; >>>> struct iio_device *dev; >>>> struct iio_channel *ch; >>>> >>>> int main() >>>> { >>>> ctx = iio_create_default_context(); >>>> dev = iio_context_get_device(ctx, 0); >>>> ch = iio_device_get_channel(dev, 3); >>>> >>>> >>>> iio_device_attr_write_longlong(dev, "sample_rate", 100); >>>> iio_channel_attr_write_double(ch, "scale", 1); >>>> >>>> iio_channel_enable(ch); >>>> >>>> char *a = iio_device_get_data(dev); >>>> printf("%p\n", a); >>>> >>>> iio_channel_disable(ch); >>>> >>>> return 0; >>>> } >>>> >>>> Thanks >>>> >>>> Pierrick >>>> >>>> >>>> Le lundi 26 février 2018 16:46:11 UTC-5, john3909 a écrit : >>>> The IIO ADC driver can run at 800K samples per second. Here is the patch >>>> that made that possible. >>>> >>>> https://patchwork.kernel.org/patch/9391487/ >>>> <https://patchwork.kernel.org/patch/9391487/> >>>> >>>> I can confirm that I have tested the driver at 800Ksps and it works fine >>>> as long as you have a proper low impedance source for each ADC channel. >>>> CPU utilization was about 5% if I recall and that was probably used by the >>>> iiod daemon, which I used to display the waveform on a remote Linux app. >>>> >>>> There is example code in the original Starterware for McSPI, which should >>>> work fine if you are using the PRU low level drivers. >>>> >>>> Regards, >>>> John >>>> >>>> >>>> >>>> >>>>> On Feb 26, 2018, at 12:56 PM, pierric...@gadz.org <> wrote: >>>>> >>>>> Thanks John, >>>>> >>>>> I am now working with the starterware_PRU but i did not find examples for >>>>> using the McSPI with the PRU, do you think it will be hard to adapt the >>>>> initial code to the PRU ? >>>>> By the way, looking to the IIO driver documentation, it seems that for >>>>> the AM335x chip the max sampling rate is only 200k samples per second >>>>> which may not be enough : >>>>> http://processors.wiki.ti.com/index.php/Linux_Core_ADC_Users_Guide >>>>> <http://processors.wiki.ti.com/index.php/Linux_Core_ADC_Users_Guide> ; am >>>>> I right ? >>>>> >>>>> >>>>> Thanks >>>>> >>>>> Pierrick >>>>> >>>>> Le lundi 19 février 2018 23:15:50 UTC-5, john3909 a écrit : >>>>> Like I said, it was based on Starterware, so search Github for >>>>> starterware and you will see a project starterware_PRU. It does use the >>>>> mcspi, so it is not a bitbang implementation. >>>>> >>>>> Regards, >>>>> John >>>>> >>>>> >>>>> >>>>> >>>>>> On Feb 19, 2018, at 7:33 PM, pierric...@gadz.org <> wrote: >>>>>> >>>>>> Thanks John for you answer, I was quit busy last week so I worked on >>>>>> this during the Weekend. >>>>>> >>>>>> Unfortunately, I was not able to find a project that is using the SPI >>>>>> and I2C interface with the PRU, I only found this one : >>>>>> https://github.com/chanakya-vc/PRU-I2C_SPI_master/wiki/SPI-Master-Controller >>>>>> >>>>>> <https://github.com/chanakya-vc/PRU-I2C_SPI_master/wiki/SPI-Master-Controller> >>>>>> >>>>>> But it is using bit banging for the SPI part and not using the on-board >>>>>> pull-up resistors for the I2C part. >>>>>> >>>>>> Concerning the ADC, I'll have a loook at the UIIO drivers in the coming >>>>>> days it seems that it meets my need in term of real-time acquisition. >>>>>> >>>>>> Regards, >>>>>> >>>>>> Pierrick >>>>>> >>>>>> -- >>>>>> 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 <>. >>>>>> To view this discussion on the web visit >>>>>> https://groups.google.com/d/msgid/beagleboard/74949832-b67c-430f-811e-f3b2fff83852%40googlegroups.com >>>>>> >>>>>> <https://groups.google.com/d/msgid/beagleboard/74949832-b67c-430f-811e-f3b2fff83852%40googlegroups.com?utm_medium=email&utm_source=footer>. >>>>>> 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. 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https://groups.google.com/d/msgid/beagleboard/18b69929-99ca-4e7e-8539-df962a17941d%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/beagleboard/18b69929-99ca-4e7e-8539-df962a17941d%40googlegroups.com?utm_medium=email&utm_source=footer>. >>>> 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 beagleboard...@googlegroups.com <>. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/beagleboard/940610ad-a88c-4918-a3e2-15d7c88d77d1%40googlegroups.com >>> >>> <https://groups.google.com/d/msgid/beagleboard/940610ad-a88c-4918-a3e2-15d7c88d77d1%40googlegroups.com?utm_medium=email&utm_source=footer>. >>> 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 beagleboard...@googlegroups.com <>. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/beagleboard/ef59523c-02ab-4c58-992a-2b37c0744ff0%40googlegroups.com >> >> <https://groups.google.com/d/msgid/beagleboard/ef59523c-02ab-4c58-992a-2b37c0744ff0%40googlegroups.com?utm_medium=email&utm_source=footer>. >> 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 beagleboard+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@googlegroups.com>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/beagleboard/54c182f4-07cc-4d61-ac1a-6cfd077eec53%40googlegroups.com > > <https://groups.google.com/d/msgid/beagleboard/54c182f4-07cc-4d61-ac1a-6cfd077eec53%40googlegroups.com?utm_medium=email&utm_source=footer>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. > <8 average sin1hz 1000sample.png><8 average > 20kHz.png><iio_generic_buffer_back.c> -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" 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