Dynomotion

Group: DynoMotion Message: 5043 From: himykabibble Date: 5/23/2012
Subject: Wierd I/O Problem...
Tom,

I did a large re-wiring of my system today, which was about 95% successful. I moved the X/Y/Z/A axes from step generators 0-3 on JP7 over to step generators 4-7 on JP5, made all the necessary software changes (in my C code and my controller app), and it all pretty much just came up and worked on the first try. I also added a B axis on step generator 0 on JP7, and that also just came up and worked. My one problem is my pendant. It was connected to JP5, using I/Os 36-42. I moved it over to JP6, using I/Os 29-35. When I disconnect the I/Os, the pendant works fine (monitoring the signals with a DVM). But, when I connect it to the KFlop JP6 I/Os, none of the signals ever come high - all are stuck well below 1V, and show no significant change when I change any of the controls on the pendant. The I/Os are all TTL signals, driven by 74LS series drivers (74LS14, IIRC). I am configuring all the I/Os as inputs in my Init. The pendant itself seems perfectly happy - all LEDs work correctly, etc., but the output signals to the KFlop seem to be getting clamped or something. Does this make any sense to you? Any suggestions? It always worked just fine on JP5.....

Regards,
Ray L.
Group: DynoMotion Message: 5044 From: Tom Kerekes Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Hi Ray,
 
The first 8 IO pins on JP6 (and JP4) have 150ohm termination resistors (pull downs).  To pull those high takes quite a bit of current (about 16ma).  A 74LS14 can sink current well but not source it well.  IO 34 and 35 do not have termination resistors so those should go high.
 
Regards,
TK

Group: DynoMotion Message: 5045 From: himykabibble Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Tom,

Can I remove those pulldowns, or at least make them large enough for the pendant to be able to pull them down? I don't really have any other good places to move the pendant to - I'm starting to run out of I/Os.....

Regards,
Ray L.

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Ray,
>  
> The first 8 IO pins on JP6 (and JP4) have 150ohm termination resistors (pull downs).  To pull those high takes quite a bit of current (about 16ma).  A 74LS14 can sink current well but not source it well.  IO 34 and 35 do not have termination resistors so those should go high.
>  
> Regards,
> TK
>
>
> ________________________________
> From: himykabibble <jagboy@...>
> To: DynoMotion@yahoogroups.com
> Sent: Wednesday, May 23, 2012 2:10 PM
> Subject: [DynoMotion] Wierd I/O Problem...
>
>
>  
> Tom,
>
> I did a large re-wiring of my system today, which was about 95% successful. I moved the X/Y/Z/A axes from step generators 0-3 on JP7 over to step generators 4-7 on JP5, made all the necessary software changes (in my C code and my controller app), and it all pretty much just came up and worked on the first try. I also added a B axis on step generator 0 on JP7, and that also just came up and worked. My one problem is my pendant. It was connected to JP5, using I/Os 36-42. I moved it over to JP6, using I/Os 29-35. When I disconnect the I/Os, the pendant works fine (monitoring the signals with a DVM). But, when I connect it to the KFlop JP6 I/Os, none of the signals ever come high - all are stuck well below 1V, and show no significant change when I change any of the controls on the pendant. The I/Os are all TTL signals, driven by 74LS series drivers (74LS14, IIRC). I am configuring all the I/Os as inputs in my Init. The pendant itself seems perfectly happy -
> all LEDs work correctly, etc., but the output signals to the KFlop seem to be getting clamped or something. Does this make any sense to you? Any suggestions? It always worked just fine on JP5.....
>
> Regards,
> Ray L.
>
Group: DynoMotion Message: 5046 From: himykabibble Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Tom,

That also raises the question: What do you expect people to be driving those inputs with? It would take at least 22mA to pull them up to 3.3V, which is at the high end of what most common logic drivers will do. Why such uber-stiff pull-downs?

Regards,
Ray L.

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Ray,
>  
> The first 8 IO pins on JP6 (and JP4) have 150ohm termination resistors (pull downs).  To pull those high takes quite a bit of current (about 16ma).  A 74LS14 can sink current well but not source it well.  IO 34 and 35 do not have termination resistors so those should go high.
>  
> Regards,
> TK
>
>
> ________________________________
> From: himykabibble <jagboy@...>
> To: DynoMotion@yahoogroups.com
> Sent: Wednesday, May 23, 2012 2:10 PM
> Subject: [DynoMotion] Wierd I/O Problem...
>
>
>  
> Tom,
>
> I did a large re-wiring of my system today, which was about 95% successful. I moved the X/Y/Z/A axes from step generators 0-3 on JP7 over to step generators 4-7 on JP5, made all the necessary software changes (in my C code and my controller app), and it all pretty much just came up and worked on the first try. I also added a B axis on step generator 0 on JP7, and that also just came up and worked. My one problem is my pendant. It was connected to JP5, using I/Os 36-42. I moved it over to JP6, using I/Os 29-35. When I disconnect the I/Os, the pendant works fine (monitoring the signals with a DVM). But, when I connect it to the KFlop JP6 I/Os, none of the signals ever come high - all are stuck well below 1V, and show no significant change when I change any of the controls on the pendant. The I/Os are all TTL signals, driven by 74LS series drivers (74LS14, IIRC). I am configuring all the I/Os as inputs in my Init. The pendant itself seems perfectly happy -
> all LEDs work correctly, etc., but the output signals to the KFlop seem to be getting clamped or something. Does this make any sense to you? Any suggestions? It always worked just fine on JP5.....
>
> Regards,
> Ray L.
>
Group: DynoMotion Message: 5047 From: Tom Kerekes Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Hi Ray,
 
Yes those are very stiff.  The aux ports were designed to talk to things like our SnapAmp that passes lots of data packets back and forth at 64Mbits/sec so the termination is really needed.  A valid TTL (both 5V TTL and 3.3V LVTTL) is only 2.4V so only about 16ma is needed.  There are lots of driver chips that will source and sink 16ma.  I wouldn't want you to remove the resistors and make a non-standard KFLOP.  It would probably work if you added 300 ohm pull ups to +5V.  The 74LS14 can sink 16ma of current.
 
Regards
TK
 
 

Group: DynoMotion Message: 5048 From: Tom Kerekes Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Hi Ray,
 
Actually a 74LVC14 will source and sink 24ma if it is possible to replace those.
 
Regards
TK
 
Group: DynoMotion Message: 5049 From: himykabibble Date: 5/23/2012
Subject: Re: Wierd I/O Problem...
Tom,

I just got done dissecting the pendant (no small task, as it was NOT designed to ever be taken apart....), and adding the pull-ups. Oddly, it tool 220 ohms to get them to juuuuuuuust barely pull up to 2V. It's really marginal but seems to be working. A pendant replacement is in my near future....

Regards,
Ray L.

--- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@...> wrote:
>
> Hi Ray,
>  
> Actually a 74LVC14 will source and sink 24ma if it is possible to replace those.
>  
> Regards
> TK
>  
>
> ________________________________
> From: himykabibble <jagboy@...>
> To: DynoMotion@yahoogroups.com
> Sent: Wednesday, May 23, 2012 2:36 PM
> Subject: [DynoMotion] Re: Wierd I/O Problem...
>
>
>  
> Tom,
>
> That also raises the question: What do you expect people to be driving those inputs with? It would take at least 22mA to pull them up to 3.3V, which is at the high end of what most common logic drivers will do. Why such uber-stiff pull-downs?
>
> Regards,
> Ray L.
>
> --- In DynoMotion@yahoogroups.com, Tom Kerekes <tk@> wrote:
> >
> > Hi Ray,
> >  
> > The first 8 IO pins on JP6 (and JP4) have 150ohm termination resistors (pull downs).  To pull those high takes quite a bit of current (about 16ma).  A 74LS14 can sink current well but not source it well.  IO 34 and 35 do not have termination resistors so those should go high.
> >  
> > Regards,
> > TK
> >
> >
> > ________________________________
> > From: himykabibble <jagboy@>
> > To: DynoMotion@yahoogroups.com
> > Sent: Wednesday, May 23, 2012 2:10 PM
> > Subject: [DynoMotion] Wierd I/O Problem...
> >
> >
> >  
> > Tom,
> >
> > I did a large re-wiring of my system today, which was about 95% successful. I moved the X/Y/Z/A axes from step generators 0-3 on JP7 over to step generators 4-7 on JP5, made all the necessary software changes (in my C code and my controller app), and it all pretty much just came up and worked on the first try. I also added a B axis on step generator 0 on JP7, and that also just came up and worked. My one problem is my pendant. It was connected to JP5, using I/Os 36-42. I moved it over to JP6, using I/Os 29-35. When I disconnect the I/Os, the pendant works fine (monitoring the signals with a DVM). But, when I connect it to the KFlop JP6 I/Os, none of the signals ever come high - all are stuck well below 1V, and show no significant change when I change any of the controls on the pendant. The I/Os are all TTL signals, driven by 74LS series drivers (74LS14, IIRC). I am configuring all the I/Os as inputs in my Init. The pendant itself seems perfectly happy -
> > all LEDs work correctly, etc., but the output signals to the KFlop seem to be getting clamped or something. Does this make any sense to you? Any suggestions? It always worked just fine on JP5.....
> >
> > Regards,
> > Ray L.
> >
>