[L2Ork-dev] 2 SPI slaves in RbPi2
Ivica Ico Bukvic
ico at vt.edu
Sat Jul 11 10:00:57 UTC 2015
Thank you for the clarification. In that case, it seem there is nothing
else we can do on our end other than hope that Linux folks improve on
their I2C implementation.
On 7/10/2015 7:51 AM, Luis G Angel wrote:
> Yes it work with 16 channel running at the same time (via opening 2
> devices, 8 channels each). The problem is the actual SPI linux library
> only instance 2 of the 3 SPI devices available in the PI’s hardware,
> in order to that we only can use 2 SPI devices. If you want more SPI
> devices there are two ways: you write your own SPI library and use any
> other GPIO pins as slave select or modify the actual SPI linux library
> (I thinks it is in the kernel, but don’t know).
> Luis G
>> El 09/07/2015, a las 4:49 a.m., Ivica Ico Bukvic <ico at vt.edu
>> <mailto:ico at vt.edu>> escribió:
>> Thank you for the follow-up, Luis. If I understand you correctly,
>> does the disis_spi therefore work for at least 16 channels (via
>> opening 2 devices, 8 channels each) or it does not work at all?
>> disis_spi has its own implementation of accessing spidevs, and
>> (AFAIR) it should not have any limitations as far as how many devices
>> can be opened at once (obviously, you will need one instance per
>> device). Perhaps the limitation you speak of is hardware-specific?
>> On 7/9/2015 3:42 AM, Luis Gerardo Angel S. wrote:
>>> I probe the program, you were right you can specify the device and
>>> it just work(attached example).
>>> The controller have 3 chip selectors for the SPI (three slaves),
>>> although you can only connect two devices according to this:
>>> http://elinux.org/RPi_SPI. You can confirm it with "ls /dev"
>>> command, there are only two SPI devices.
>>> I read in some forum (can't remember which ones) this is due to how
>>> the library was written leaving out the third chip selector.
>>> At the present time the only way to connect more SPI devices is:
>>> write your own SPI library (maybe with wiringPi) and use the GPIO's
>>> general purpose(pardon the redundancy) pins like selectors. It would
>>> be nice we can use the third selector with another "/dev/spidev0.2"
>>> in that way the external does not have to be modified and 24 analog
>>> inputs would be very good.
>>> Luis G
>>> On mié, jul 8, 2015 at 3:49 , Ivica Ico Bukvic <ico at vt.edu> wrote:
>>>> Hi Luis, I am not 100% sure but if I recall correctly, you can
>>>> specify which device you wish to open, so as long as each device is
>>>> assigned a different /dev node, this should work just fine. I would
>>>> appreciate it if you would please report your results and let us
>>>> know. Alternately, there are larger D/A converters that provide you
>>>> with more inputs, but will also require a customized version of
>>>> disis_spi. Hope this helps! Best, Ico On 7/7/2015 11:41 PM, Luis G
>>>> Angel wrote:
>>>> Hi list I want to use two MCP3008 in order to connect 16 analog
>>>> inputs to the Pi2, so my question is if the [disis_spi] is
>>>> capable to manage 2 slaves. If it is, how it should be the
>>>> patch to manage that. Thanks for any idea Luis G
>>>> _______________________________________________ L2Ork-dev
>>>> mailing list L2Ork-dev at disis.music.vt.edu
>>>> Ivica Ico Bukvic, D.M.A. Associate Professor Computer Music ICAT
>>>> Senior Fellow Director -- DISIS, L2Ork Virginia Tech School of
>>>> Performing Arts – 0141 Blacksburg, VA 24061 (540) 231-6139
>>>> ico at vt.edu www.performingarts.vt.edu
>>>> <http://www.performingarts.vt.edu/> disis.icat.vt.edu
>>>> <http://disis.icat.vt.edu> l2ork.icat.vt.edu
>>>> _______________________________________________ L2Ork-dev mailing
>>>> list L2Ork-dev at disis.music.vt.edu
>> Ivica Ico Bukvic, D.M.A.
>> Associate Professor
>> Computer Music
>> ICAT Senior Fellow
>> Director -- DISIS, L2Ork
>> Virginia Tech
>> School of Performing Arts – 0141
>> Blacksburg, VA 24061
>> (540) 231-6139
>> ico at vt.edu
>> disis.icat.vt.edu <http://disis.icat.vt.edu>
>> l2ork.icat.vt.edu <http://l2ork.icat.vt.edu>
Ivica Ico Bukvic, D.M.A.
ICAT Senior Fellow
Director -- DISIS, L2Ork
School of Performing Arts – 0141
Blacksburg, VA 24061
ico at vt.edu
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