Re: [Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

No, I don't have any Probotix systems, just one of their PBX-BB capes.  I 
use
these capes and BBB's in my Manufacturing Systems lab for student automation
projects.  We just hook up AutomationDirect stepper drives and some surplus
linear motion stages retrofitted to steppers, along with some 24v prox 
sensors
for homing.

On Friday, January 13, 2017 at 8:12:01 AM UTC-8, Harley Engholm wrote:
>
> I will check out the config files. Are you running the BBB on a Comet? How 
> much are you asking for the boards?
> Harley
>
> On Thursday, January 12, 2017 at 8:08:18 PM UTC-8, Ralph Stirling wrote:
>>
>> It was such a simple design that I didn't bother with a BOM.
>> I started with the Probotix config files, but can't guarantee
>> that my board is still completely compatible with the PBX-BB.
>> The "engr480a" hal and ini files work with my board.
>>
>> -- Ralph
>>
>> On Thursday, January 12, 2017 at 11:20:27 AM UTC-8, Harley Engholm wrote:
>>>
>>> Do you have a BOM for the board and will the configuration files for 
>>> Comet_NP for the PBC BB work and how much for the PCB? Looks like a good, 
>>> simple setup.
>>> Harley 
>>>
>>> On Thursday, January 12, 2017 at 10:43:44 AM UTC-8, Ralph Stirling wrote:
>>>>
>>>> I made one mistake on the (hasty) board layout I did, which requires 
>>>> pullup resistors
>>>> to be added to the digital input pins at the BBB headers, but otherwise 
>>>> they did the
>>>> job for me.  They are nothing fancy.  You can look at my documentation 
>>>> at:
>>>> http://gab.wallawalla.edu/~ralph.stirling/misc/bbbcape to see if you 
>>>> are still interested
>>>> in a blank board.
>>>>
>>>> -- Ralph
>>>>
>>>> On Thursday, January 12, 2017 at 10:36:44 AM UTC-8, Harley Engholm 
>>>> wrote:
>>>>>
>>>>> Have the boards you had made worked well for a probotix type setup? I 
>>>>> have a V90 and an asteroid and am now working on a diy engraver that I 
>>>>> want 
>>>>> to use the BBB on. Finding capes for CNC only instead of 3D printer 
>>>>> setups 
>>>>> has been a challenge. I would be especially interested in your board 
>>>>> since 
>>>>> it seems you are working on the same type of equipment. I contacted Len 
>>>>> and 
>>>>> he said the new version of the PBX BB won't be available for at least a 
>>>>> couple of months.
>>>>> Harley
>>>>>
>>>>> On Sunday, September 18, 2016 at 10:24:39 AM UTC-7, Ralph Stirling 
>>>>> wrote:
>>>>>>
>>>>>> Not finding anything available that I liked, I have designed a simple 
>>>>>> cape myself
>>>>>> and will be getting a batch fabricated this week.  Would anybody on 
>>>>>> the list be
>>>>>> interested in buying a bare board for $15 each (+ shipping if outside 
>>>>>> US)?
>>>>>>
>>>>>> I use a cheap LM2596 dc-dc converter module off ebay for powering 
>>>>>> everything,
>>>>>> and Toshiba TBD62083 drivers to provide protection for the BBB. 
>>>>>>  These are
>>>>>> open-collector, so loads need to be +V referenced.  The +V can be 
>>>>>> 5-24V.  The
>>>>>> step/dir signals are intended to drive 5v inputs, but the GP outputs 
>>>>>> are intended
>>>>>> for 24v loads (but can switch lower voltages fine).  The inputs are 
>>>>>> 24v capable.
>>>>>>
>>>>>> I designed it to work with the Probotix Comet configuration (as I 
>>>>>> already have a
>>>>>> PBX-BB board) for step/dir and home/limit connections.  The general 
>>>>>> purpose
>>>>>> outputs will need additions to the hal file.
>>>>>>
>>>>>> -- Ralph
>>>>>>
>>>>>> On Thursday, September 15, 2016 at 8:38:15 PM UTC-7, Ralph Stirling 
>>>>>> wrote:
>>>>>>>
>>>>>>> I came across this oddity while poking around this evening:
>>>>>>>
>>>>>>> http://www.waveshare.com/CAPE-for-Arduino.htm
>>>>>>>
>>>>>>> The price is right, the claims sound good, but how does this
>>>>>>> thing handle 5V arduino pe

Re: [Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

It was such a simple design that I didn't bother with a BOM.
I started with the Probotix config files, but can't guarantee
that my board is still completely compatible with the PBX-BB.
The "engr480a" hal and ini files work with my board.

-- Ralph

On Thursday, January 12, 2017 at 11:20:27 AM UTC-8, Harley Engholm wrote:
>
> Do you have a BOM for the board and will the configuration files for 
> Comet_NP for the PBC BB work and how much for the PCB? Looks like a good, 
> simple setup.
> Harley 
>
> On Thursday, January 12, 2017 at 10:43:44 AM UTC-8, Ralph Stirling wrote:
>>
>> I made one mistake on the (hasty) board layout I did, which requires 
>> pullup resistors
>> to be added to the digital input pins at the BBB headers, but otherwise 
>> they did the
>> job for me.  They are nothing fancy.  You can look at my documentation at:
>> http://gab.wallawalla.edu/~ralph.stirling/misc/bbbcape to see if you are 
>> still interested
>> in a blank board.
>>
>> -- Ralph
>>
>> On Thursday, January 12, 2017 at 10:36:44 AM UTC-8, Harley Engholm wrote:
>>>
>>> Have the boards you had made worked well for a probotix type setup? I 
>>> have a V90 and an asteroid and am now working on a diy engraver that I want 
>>> to use the BBB on. Finding capes for CNC only instead of 3D printer setups 
>>> has been a challenge. I would be especially interested in your board since 
>>> it seems you are working on the same type of equipment. I contacted Len and 
>>> he said the new version of the PBX BB won't be available for at least a 
>>> couple of months.
>>> Harley
>>>
>>> On Sunday, September 18, 2016 at 10:24:39 AM UTC-7, Ralph Stirling wrote:
>>>>
>>>> Not finding anything available that I liked, I have designed a simple 
>>>> cape myself
>>>> and will be getting a batch fabricated this week.  Would anybody on the 
>>>> list be
>>>> interested in buying a bare board for $15 each (+ shipping if outside 
>>>> US)?
>>>>
>>>> I use a cheap LM2596 dc-dc converter module off ebay for powering 
>>>> everything,
>>>> and Toshiba TBD62083 drivers to provide protection for the BBB.  These 
>>>> are
>>>> open-collector, so loads need to be +V referenced.  The +V can be 
>>>> 5-24V.  The
>>>> step/dir signals are intended to drive 5v inputs, but the GP outputs 
>>>> are intended
>>>> for 24v loads (but can switch lower voltages fine).  The inputs are 24v 
>>>> capable.
>>>>
>>>> I designed it to work with the Probotix Comet configuration (as I 
>>>> already have a
>>>> PBX-BB board) for step/dir and home/limit connections.  The general 
>>>> purpose
>>>> outputs will need additions to the hal file.
>>>>
>>>> -- Ralph
>>>>
>>>> On Thursday, September 15, 2016 at 8:38:15 PM UTC-7, Ralph Stirling 
>>>> wrote:
>>>>>
>>>>> I came across this oddity while poking around this evening:
>>>>>
>>>>> http://www.waveshare.com/CAPE-for-Arduino.htm
>>>>>
>>>>> The price is right, the claims sound good, but how does this
>>>>> thing handle 5V arduino peripherals without any active (or
>>>>> passive for that matter) circuitry?  The schematic just shows
>>>>> the arduino sockets connected to BBB pins through selectively
>>>>> stuffed 0 ohm resistors.  Looks like a good way to burn up a
>>>>> BBB.  Am I missing something?  Back to my Kicad session...
>>>>>
>>>>>
>>>>> On Thursday, September 15, 2016 at 6:35:24 PM UTC-7, Dave Cole wrote:
>>>>>>
>>>>>> I was in a plant where they make a large number of boards on multiple 
>>>>>> lines and I looked at their automatic test fixtures that probe the 
>>>>>> boards... and all of them were wire wrapped!So maybe not "that" 
>>>>>> retro!  
>>>>>> :-)  
>>>>>>
>>>>>> Dave
>>>>>>
>>>>>> On 9/15/2016 8:28 PM, Ralph Stirling wrote:
>>>>>>
>>>>>> You would have to suggest hand wiring :-).  The proto capes I've seen 
>>>>>> don't look big 
>>>>>> enough for the dip buffer chips and connectors, but I'll look at that 
>>>>>> option a little bit more.
>>>>>> I guess I could u

Re: [Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

I made one mistake on the (hasty) board layout I did, which requires pullup 
resistors
to be added to the digital input pins at the BBB headers, but otherwise 
they did the
job for me.  They are nothing fancy.  You can look at my documentation at:
http://gab.wallawalla.edu/~ralph.stirling/misc/bbbcape to see if you are 
still interested
in a blank board.

-- Ralph

On Thursday, January 12, 2017 at 10:36:44 AM UTC-8, Harley Engholm wrote:
>
> Have the boards you had made worked well for a probotix type setup? I have 
> a V90 and an asteroid and am now working on a diy engraver that I want to 
> use the BBB on. Finding capes for CNC only instead of 3D printer setups has 
> been a challenge. I would be especially interested in your board since it 
> seems you are working on the same type of equipment. I contacted Len and he 
> said the new version of the PBX BB won't be available for at least a couple 
> of months.
> Harley
>
> On Sunday, September 18, 2016 at 10:24:39 AM UTC-7, Ralph Stirling wrote:
>>
>> Not finding anything available that I liked, I have designed a simple 
>> cape myself
>> and will be getting a batch fabricated this week.  Would anybody on the 
>> list be
>> interested in buying a bare board for $15 each (+ shipping if outside US)?
>>
>> I use a cheap LM2596 dc-dc converter module off ebay for powering 
>> everything,
>> and Toshiba TBD62083 drivers to provide protection for the BBB.  These are
>> open-collector, so loads need to be +V referenced.  The +V can be 5-24V. 
>>  The
>> step/dir signals are intended to drive 5v inputs, but the GP outputs are 
>> intended
>> for 24v loads (but can switch lower voltages fine).  The inputs are 24v 
>> capable.
>>
>> I designed it to work with the Probotix Comet configuration (as I already 
>> have a
>> PBX-BB board) for step/dir and home/limit connections.  The general 
>> purpose
>> outputs will need additions to the hal file.
>>
>> -- Ralph
>>
>> On Thursday, September 15, 2016 at 8:38:15 PM UTC-7, Ralph Stirling wrote:
>>>
>>> I came across this oddity while poking around this evening:
>>>
>>> http://www.waveshare.com/CAPE-for-Arduino.htm
>>>
>>> The price is right, the claims sound good, but how does this
>>> thing handle 5V arduino peripherals without any active (or
>>> passive for that matter) circuitry?  The schematic just shows
>>> the arduino sockets connected to BBB pins through selectively
>>> stuffed 0 ohm resistors.  Looks like a good way to burn up a
>>> BBB.  Am I missing something?  Back to my Kicad session...
>>>
>>>
>>> On Thursday, September 15, 2016 at 6:35:24 PM UTC-7, Dave Cole wrote:
>>>>
>>>> I was in a plant where they make a large number of boards on multiple 
>>>> lines and I looked at their automatic test fixtures that probe the 
>>>> boards... and all of them were wire wrapped!So maybe not "that" retro! 
>>>>  
>>>> :-)  
>>>>
>>>> Dave
>>>>
>>>> On 9/15/2016 8:28 PM, Ralph Stirling wrote:
>>>>
>>>> You would have to suggest hand wiring :-).  The proto capes I've seen 
>>>> don't look big 
>>>> enough for the dip buffer chips and connectors, but I'll look at that 
>>>> option a little bit more.
>>>> I guess I could use generic perf board material while I'm at it.  I 
>>>> wonder if I have enough
>>>> wire-wrap sockets and wire to go really retro?
>>>>
>>>> On Thursday, September 15, 2016 at 5:09:09 PM UTC-7, Charles 
>>>> Steinkuehler wrote: 
>>>>>
>>>>> On 9/15/2016 5:27 PM, Ralph Stirling wrote: 
>>>>> > I have decided to use Machinekit running on BBB's in my 
>>>>> Manufacturing Systems 
>>>>> > course for 
>>>>> > senior ME students.  I've been using old PC's running Linuxcnc the 
>>>>> past several 
>>>>> > years, and 
>>>>> > the old PC's have been failing.  They also take up a lot of space in 
>>>>> the lab. 
>>>>> >   I've got one 
>>>>> > Probotix PBX-BB cape, which is perfect for my needs, but Len is out 
>>>>> of stock on 
>>>>> > them, and 
>>>>> > won't have any before his design revision in 3-4 months.  I have 
>>>>> external 
>>>>> > stepper drivers. 
>>>>> > 
>>>>> > Does anybody know of any capes that ar

[Machinekit] Re: DB25 CAPE/breakout board for MachineKit? Perhaps open-source design?

[Ralph Stirling]

Hi Oliver,

I designed a simple cape a few months ago and had 20 boards fabbed.
It uses TBD62083 buffer chips for 5-24V I/O.  I designed it with KiCad.
I found one mistake on it, and have to add pull up resistors to eight
pins.  If you'd be interested in either a bare pcb or just the KiCad files,
I'm happy to share.  I even have a few extras with all the smd components
soldered on if I recall.

-- Ralph

On Wednesday, January 4, 2017 at 10:20:36 AM UTC-8, Oliver Rew wrote:
>
> Hi there, I am interested in getting started with MachineKit, and the 
> website shows a bunch of Capes for machinekit, but all the simple 
> DB25/parallel boards are out of stock at there respective websites. There 
> are a few complicated/professional ones, but there are all expensive and 
> overkill for my level of experience at this time. Does anyone know of any 
> other place that sells something similar? Better yet, does anyone know of 
> an open-source or available board design for such a Cape that I could send 
> to OSH Park and then solder myself? Would be a very simple design, just a 
> few buffer/line driver chips, DB25 header, and a handful of passives? I 
> could perhaps design one myself, but I am fairly new to EE and am an 
> amateur at Eagle. Thanks!
>

-- 
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https://github.com/machinekit
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[Machinekit] Re: Hardware choice for industrial application

[Ralph Stirling]

Not quite what you were asking, Bas, but I had one team of students in my
Manufacturing Automation class use Machinekit on a BBB along with an
AutomationDirect PLC for an assembly task.  Other than a few random freezes
or lockups, it worked pretty well.  Cape was a custom one I designed.

Writeup is here: 
https://gab.wallawalla.edu/~ralph.stirling/classes/engr480/reports/proj2016/team_schlinsog.pdf
Video is here:
https://www.youtube.com/watch?v=0oW7rzqR7wk

I hope to do more automation with Machinekit in future years.  PC's in 
control
cabinets are fine, but if you use a bare motherboard you need to figure out
how to secure the PCI(-E) card in place.  In a project a couple of years ago
we used a "CT100 Mountable Open Case" from Logic Supply to put a motherboard
inside a cabinet.  We used a 7I90 and parallel port in that project.  Mesa 
cards
were DIN rail mounted.

-- Ralph

On Monday, December 19, 2016 at 12:48:25 PM UTC-8, Bas de Bruijn wrote:
>
> Hi,
>
> I’m making a non-cnc type application and would choose Machinekit over a 
> PLC with motion card.
> I hope there are people on this list who have some advice regarding the 
> choice for hardware.
> Especially experiences with PC’s inside an electrical control cabinet 
> would be most welcome.
>
> I’d like to use the Mesa 7i76 cards.
>
> What pitfall (if any) would I need to be aware of for choosing 6i25 or 
> 5i25 card in combination with the PC. Would this be a viable choice 
> http://www.logicsupply.com/mc600-10/#specs ?
>
> Cheers,
> Bas
>

-- 
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https://github.com/machinekit
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[Machinekit] Re: running ngc code without gui

[Ralph Stirling]

Thanks Marius and automata!  These are very helpful leads.  I will pursue 
them when a window
of time opens later.  I also found another possibility from a post Charles 
made this morning on
another thread.  Machinekit Axis has a few extensions not present in the 
legacy LinuxCNC version.
One of these is a "-R" command line option which will run an ngc file upon 
starting.  So I have
three options to try out when I get some time.

Thanks again everyone!  I'll report back when I actually have something 
working.

-- Ralph

On Tuesday, November 29, 2016 at 10:39:44 PM UTC-8, Marius Alksnys wrote:
>
> In INI I use: 
> DISPLAY = mkwrapper 
> Source: 
> https://github.com/machinekit/machinekit/tree/master/src/machinetalk 
>
> and in hal: 
> loadusr -W haltalk 
>
> And I create two services. One for machinetalk and another to start 
> machinekit by following these instructions: 
>
> https://github.com/machinekoder/asciidoc-sandbox/blob/master/Starting-a-Machinekit-configuration-at-boot.md
>  
>
> This way machinekit starts after boot. 
>
> You can also check sample Cetus and Machineface configs. 
>
> 11/15/2016 06:48 AM, Ralph Stirling rašė: 
> > I am interested in using Machinekit BBB's as "automation appliances" in 
> > my Manufacturing Systems lab.  Axis is handy for getting everything 
> > going, but once the program, I/O, and HAL configuration are figured out, 
> > it would be nice to unplug from the host PC and have it run headless. 
> > 
> > I can put a script in /etc/init.d, but haven't found a simple non-gui 
> way of 
> > running G-code.  I've looked at halcmd, hal_ui, and hal_run, but setting 
> > everything up to read and run an ngc file appears daunting.  Ideally I'd 
> > like a program I can run from the command line, with arguments for the 
> > ngc, ini, and hal files. 
> > 
> > Any suggestions or examples? 
> > 
> > Thanks, 
> > -- Ralph 
> > 
>
>

-- 
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https://github.com/machinekit
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[Machinekit] running ngc code without gui

[Ralph Stirling]

I am interested in using Machinekit BBB's as "automation appliances" in
my Manufacturing Systems lab.  Axis is handy for getting everything
going, but once the program, I/O, and HAL configuration are figured out,
it would be nice to unplug from the host PC and have it run headless.

I can put a script in /etc/init.d, but haven't found a simple non-gui way of
running G-code.  I've looked at halcmd, hal_ui, and hal_run, but setting
everything up to read and run an ngc file appears daunting.  Ideally I'd
like a program I can run from the command line, with arguments for the
ngc, ini, and hal files.

Any suggestions or examples?

Thanks,
-- Ralph

-- 
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Re: [Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

I came across this oddity while poking around this evening:

http://www.waveshare.com/CAPE-for-Arduino.htm

The price is right, the claims sound good, but how does this
thing handle 5V arduino peripherals without any active (or
passive for that matter) circuitry?  The schematic just shows
the arduino sockets connected to BBB pins through selectively
stuffed 0 ohm resistors.  Looks like a good way to burn up a
BBB.  Am I missing something?  Back to my Kicad session...


On Thursday, September 15, 2016 at 6:35:24 PM UTC-7, Dave Cole wrote:
>
> I was in a plant where they make a large number of boards on multiple 
> lines and I looked at their automatic test fixtures that probe the 
> boards... and all of them were wire wrapped!So maybe not "that" retro!  
> :-)  
>
> Dave
>
> On 9/15/2016 8:28 PM, Ralph Stirling wrote:
>
> You would have to suggest hand wiring :-).  The proto capes I've seen 
> don't look big 
> enough for the dip buffer chips and connectors, but I'll look at that 
> option a little bit more.
> I guess I could use generic perf board material while I'm at it.  I wonder 
> if I have enough
> wire-wrap sockets and wire to go really retro?
>
> On Thursday, September 15, 2016 at 5:09:09 PM UTC-7, Charles Steinkuehler 
> wrote: 
>>
>> On 9/15/2016 5:27 PM, Ralph Stirling wrote: 
>> > I have decided to use Machinekit running on BBB's in my Manufacturing 
>> Systems 
>> > course for 
>> > senior ME students.  I've been using old PC's running Linuxcnc the past 
>> several 
>> > years, and 
>> > the old PC's have been failing.  They also take up a lot of space in 
>> the lab. 
>> >   I've got one 
>> > Probotix PBX-BB cape, which is perfect for my needs, but Len is out of 
>> stock on 
>> > them, and 
>> > won't have any before his design revision in 3-4 months.  I have 
>> external 
>> > stepper drivers. 
>> > 
>> > Does anybody know of any capes that aren't already featured in the 
>> wiki?  I've 
>> > looked at 
>> > all of those, and they are either too expensive, unavailable, or too 
>> fancy.  I 
>> > just need 3 or 
>> > 4 channels of buffered step/dir, buffered home inputs, and a few 
>> gpio's.  I've 
>> > got a design 
>> > of my own underway, but only have about 3 weeks until I need to have 
>> these 
>> > running, and 
>> > don't think I can pull off my custom design in that time.  I need eight 
>> or nine 
>> > boards. 
>>
>> You could build your own manually using a prototype cape and a few 
>> through-hole buffer chips.  It sucks soldering 8-9 boards up by hand 
>> with "flying wires", but it shouldn't take more than a few hours if 
>> you're decent with a soldering iron and have the right tools (a good 
>> set of diagonal cutting pliers and a nice wire stripper). 
>>
>> -- 
>> Charles Steinkuehler 
>> cha...@steinkuehler.net 
>>
> -- 
> website: http://www.machinekit.io blog: http://blog.machinekit.io github: 
> https://github.com/machinekit
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>

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Re: [Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

You would have to suggest hand wiring :-).  The proto capes I've seen don't 
look big
enough for the dip buffer chips and connectors, but I'll look at that 
option a little bit more.
I guess I could use generic perf board material while I'm at it.  I wonder 
if I have enough
wire-wrap sockets and wire to go really retro?

On Thursday, September 15, 2016 at 5:09:09 PM UTC-7, Charles Steinkuehler 
wrote:
>
> On 9/15/2016 5:27 PM, Ralph Stirling wrote: 
> > I have decided to use Machinekit running on BBB's in my Manufacturing 
> Systems 
> > course for 
> > senior ME students.  I've been using old PC's running Linuxcnc the past 
> several 
> > years, and 
> > the old PC's have been failing.  They also take up a lot of space in the 
> lab. 
> >   I've got one 
> > Probotix PBX-BB cape, which is perfect for my needs, but Len is out of 
> stock on 
> > them, and 
> > won't have any before his design revision in 3-4 months.  I have 
> external 
> > stepper drivers. 
> > 
> > Does anybody know of any capes that aren't already featured in the wiki? 
>  I've 
> > looked at 
> > all of those, and they are either too expensive, unavailable, or too 
> fancy.  I 
> > just need 3 or 
> > 4 channels of buffered step/dir, buffered home inputs, and a few gpio's. 
>  I've 
> > got a design 
> > of my own underway, but only have about 3 weeks until I need to have 
> these 
> > running, and 
> > don't think I can pull off my custom design in that time.  I need eight 
> or nine 
> > boards. 
>
> You could build your own manually using a prototype cape and a few 
> through-hole buffer chips.  It sucks soldering 8-9 boards up by hand 
> with "flying wires", but it shouldn't take more than a few hours if 
> you're decent with a soldering iron and have the right tools (a good 
> set of diagonal cutting pliers and a nice wire stripper). 
>
> -- 
> Charles Steinkuehler 
> cha...@steinkuehler.net  
>

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[Machinekit] Simple capes for BBB/Machinekit

[Ralph Stirling]

I have decided to use Machinekit running on BBB's in my Manufacturing 
Systems course for
senior ME students.  I've been using old PC's running Linuxcnc the past 
several years, and
the old PC's have been failing.  They also take up a lot of space in the 
lab.  I've got one
Probotix PBX-BB cape, which is perfect for my needs, but Len is out of 
stock on them, and
won't have any before his design revision in 3-4 months.  I have external 
stepper drivers.

Does anybody know of any capes that aren't already featured in the wiki? 
 I've looked at
all of those, and they are either too expensive, unavailable, or too fancy. 
 I just need 3 or
4 channels of buffered step/dir, buffered home inputs, and a few gpio's. 
 I've got a design
of my own underway, but only have about 3 weeks until I need to have these 
running, and
don't think I can pull off my custom design in that time.  I need eight or 
nine boards.

Thanks for any tips.
-- Ralph

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[Machinekit] Re: Blinking an LED

[Ralph Stirling]

Luke,

We have done both single and twin inverted pendulums in our Feedback &
Control classes.  Our apparatus (our design and fabrication) has a cart 
driven
by fishing line around a pulley on a high quality DC "basket weave" motor
(Escap or Maxon).  These have zero cogging, with no steel in the rotor.  The
state space control law uses encoder feedback from the motor (for cart 
position)
and each of the pendulums.

I've wanted somebody to work on the system identification problem to collect
all the data to compute the parameters needed by the control law, but so far
we just used statically measured data or manufacturer's datasheets.

The difficulty with using a BBB for this project is that it doesn't have 
enough
counters (or drivers for them) to handle three incremental encoders.  If you
used one of the FPGA SoC boards that have been discussed on this list 
recently,
you could implement encoder counters in the FPGA.  Our inverted pendulum
setup uses a Digilent FPGA board, with a custom H-bridge and ethernet 
connection
to communicate with Octave running on a PC.  Octave does all the control
calculations and just gets encoder readings from the FPGA board, and writes
PWM values.

I think your control law will be a lot simpler, and the rest of the system 
too,
if you use velocity control rather than torque control.  Then you only need
to control your motor voltage (proportional to velocity) rather than motor
current (proportional to torque).

-- Ralph

On Wednesday, September 14, 2016 at 9:20:11 AM UTC-7, Luke Steele wrote:
>
> Hello,
>
> I should probably explain that I'm a linux and BBB novice, and am 
> currently experiencing a crazily steep learning curve. So please bear with 
> me while I ask what are probably incredibly rudimentary questions...
>
> I'm interested in doing some realtime control (servos, reading encoders 
> etc) on my BBB rev C under Xenomai, and after some reading around it seemed 
> like the simplest way to get started was using the pre-built machinekit 
> images found here: 
> http://elinux.org/Beagleboard:BeagleBoneBlack_Debian#BBW.2FBBB_.28All_Revs.29_Machinekit
>
> So, having installed this image I can now ssh into the BBB from a Xubuntu 
> install running under VMware on my PC.
>
> I thought a good place to start would be blinking an LED. To that end I've 
> compiled the C++ program here 
> ,
>  
> which works (only) if I use sudo, i.e. sudo ./myprog. I've also tried 
> turning them on and off at the command line as outlined on Derek Molloy's 
> site 
> , 
> but this doesn't work:
>
> cd /sys/class/leds
> cd beaglebone:green:usr0
> echo none > trigger
>
> -bash: trigger: Permission denied
>
> sudo echo none > trigger doesn't work either...
>
> What am I doing wrong?
>
> Also more generally, is this approach of accessing LEDs and GPIOs through 
> the file system the right way to go if I'm interested in doing things 
> quickly? Intuitively it feels like it'd be slow - is there another way?
>
> Incidentally this  
> is what I'm aiming to do eventually. 
>
> Thanks for any help, it's appreciated!
>
> Luke
>
>
>

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