> On Apr 16, 2018, at 3:40 PM, pierrick.ra...@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. >>>> 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/3dc611e5-04e7-45bb-87d4-3c21a5665cec%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/beagleboard/3dc611e5-04e7-45bb-87d4-3c21a5665cec%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/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+unsubscr...@googlegroups.com > <mailto:beagleboard+unsubscr...@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 --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. 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