Dynomotion

Group: DynoMotion Message: 9514 From: swarbrick_jon Date: 5/22/2014
Subject: FPGA setting

Hi,


Can someone please explain the FPGA setting, the examples all give 2us as an example and I am wondering if this is too fast for my Gecko 320?


thanks,


Jon
Group: DynoMotion Message: 9515 From: swarbrick_jon Date: 5/22/2014
Subject: Re: FPGA setting

I am now doubtful that this is my problem as it seems to be within the gecko specs (0.5us high an 3.5us low)...
I am trying to set up my miling machine with 3 DC Servo motors connected to Gecko 320 drivers, the encoders are also connected to the geckos.

The geckos were "working" but never tunned well previously running Mach3.

When I have that working I will add a rotory axis (or 2) which are driven by stepper motors again with Gecko drivers.

For an initial setup I am trying to get a single axis alive (X).

Step, Direction and a suitable ground (Digital Ground?) are needed by the Gecko from the Kflop.  Also there is an ERR/RST on the geckos that I will come back to as I do not seem to be able to reliably reset the gecko at them moment..

I came to the conculsion that by setting Axis 0 as no input, Step/Dir and the Output Channel=8 I should get the required Step, Direction and Ground from Pins 15,16 and 26 of J7.

With FPGA(STEP_PULSE_LENGTH_ADD)=32 + 0x80;  the signal is set to be pulsing high for 2us.  I can see this with a scope around 3.5v, I can also see the direction changes.

However there is no life in the Servo, it resists being rotated and gecko gets quite warm!!

What have I missed or am I not understanding ?

Jon
Group: DynoMotion Message: 9516 From: Tom Kerekes Date: 5/22/2014
Subject: Re: FPGA setting
Hi Jon,

Do you have the Gecko G320 or the newer G320X ??

I believe to drive the G320 the step pulse should sink current to ground (KFLOP Open Collector mode) and with the Gecko Common Pin tied to +5V.  See the little schematic on the case of the Gecko.

To change the pulse length from 2 to 3.78 us (max) use:
FPGA(STEP_PULSE_LENGTH_ADD)=63 + 0x80

HTH
Reagrds
TK

Group: DynoMotion Message: 9517 From: swarbrick_jon Date: 5/22/2014
Subject: Re: FPGA setting

Tom,


G320 not X


OK so you were 100% right, I now have a functioning axis, I did not change the  FPGA setting from 2us.


Is there a recommended way to set up the reset on ERR/RST so that I can reliably enable the Gecko to start with?  Reading the Gecko documentation it looks like I can just attach to a 5v GIO pin and raise that pin for 5 seconds to clear the Gecko but it does not seem to like that :(



Thanks,


Jon
Group: DynoMotion Message: 9518 From: Tom Kerekes Date: 5/22/2014
Subject: Re: FPGA setting
Hi Jon,

Based on:

http://www.geckodrive.com/g320-rev-7

It seems like driving that pin above 2.8V should work.  Check with a voltmeter.  You must set the IO as an Output.

Regards
TK


Group: DynoMotion Message: 9520 From: swarbrick_jon Date: 5/23/2014
Subject: Re: FPGA setting

TK.


For reference the gecko 320 does actually want 5v, but that is not high on my priority list right now.


I will close this thread (and start another immediately ;) )


IN SUMMARY


The Gecko 320 (not Gecko 320X) needs Step and Direction in KFlop's Open Collector mode and +5V for the common.


FPGA(STEP_PULSE_LENGTH_ADD)=32 + 0x80;  is needed to create a step signal that pulses high rather than the default low.



Thanks,


Jon



---In DynoMotion@yahoogroups.com, <tk@...> wrote :

Hi Jon,

Based on:

http://www.geckodrive.com/g320-rev-7

It seems like driving that pin above 2.8V should work.  Check with a voltmeter.  You must set the IO as an Output.

Regards
TK


From: "jswarbrick@... [DynoMotion]" <DynoMotion@yahoogroups.com>
To: DynoMotion@yahoogroups.com
Sent: Thursday, May 22, 2014 12:11 PM
Subject: [DynoMotion] Re: FPGA setting

 
Tom,

G320 not X

OK so you were 100% right, I now have a functioning axis, I did not change the  FPGA setting from 2us.

Is there a recommended way to set up the reset on ERR/RST so that I can reliably enable the Gecko to start with?  Reading the Gecko documentation it looks like I can just attach to a 5v GIO pin and raise that pin for 5 seconds to clear the Gecko but it does not seem to like that :(


Thanks,

Jon