[L2Ork-dev] 2 SPI slaves in RbPi2

[Luis G Angel]

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> 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?
> 
> Best,
> 
> Ico
> 
> On 7/9/2015 3:42 AM, Luis Gerardo Angel S. wrote:
>> Hi
>> 
>> 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 <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> <mailto: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
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>>>               http://disis.music.vt.edu/listinfo/l2ork-dev <http://disis.music.vt.edu/listinfo/l2ork-dev>
>>>             
>>> 
>>>             
>>> -- 
>>> 
>>>             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 <mailto:ico at vt.edu>
>>>             www.performingarts.vt.edu <http://www.performingarts.vt.edu/>
>>>             disis.icat.vt.edu
>>>             l2ork.icat.vt.edu
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> -- 
> 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 <mailto:ico at vt.edu>
> www.performingarts.vt.edu <http://www.performingarts.vt.edu/>
> disis.icat.vt.edu
> l2ork.icat.vt.edu

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