Yes, sorry, my mistake I was looking to section 12.3.3 in the TRM instead on looking to the STEPCONFIG register description sections.
Le mardi 17 avril 2018 00:19:16 UTC-4, john3909 a écrit : > > > > On Apr 16, 2018, at 3:40 PM, pierric...@gadz.org <javascript:> 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/ 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/ ) 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/ >>>> >>>> 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 ; >>>> 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 >>>>> >>>>> 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 >>>>> --- >>>>> 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. >>>>> >>>>> >>>>> >>>> -- >>>> 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. >>>> 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. >>>> >>>> >>>> >>> -- >>> 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. >>> 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. >>> >>> >>> >> -- >> 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. >> 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. >> >> >> > -- > 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 <javascript:>. > 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. > > > -- 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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