On 1/10/2014 12:33 PM, Charles Steinkuehler wrote:
Charles, sorry it took so long to get back to you on this, apparently others found 'better' uses of my time ;-)On 1/10/2014 9:33 AM, Charles Steinkuehler wrote:On 1/10/2014 7:42 AM, Thomas Studwell wrote: I can easily modify the PRU assembly and create a version that does falling-edge step pulses for all step/dir generators. To use it, you would simply point to the modified PRU binary in the HAL command that loads the hal_pru_generic module. The longest part will be actually testing the code to make sure it works as expected.OK, here's the quick and dirty version of the PRU code that just inverts the step signal. I've verified it moves motors on my 3D printer and the default step state is high (the step pulse is a falling edge, followed very briefly by a return to the default high state).Just drop it in the linuxcnc/xenomai directory and adjust your ini/hal file to load the new file (pru_generic_fall.bin). The debugging files are included just in case you feel _really_ adventurous! :) cc'd directly to the two interested parties in case the list strips the attachment. If it does, and someone else is interested in a copy of this as well, just e-mail me directly. WARNING: This is for short-term use ONLY! I expect to have updated code that will support setting the step polarity via HAL within a week or two, along with many other changes that will require significant modification to any existing configurations (but will make pin numbering a whole lot more consistent and understandable!).
The driver works as advertised! I've attached two scope traces, one taken with the original driver (Y_Step_Pos.png) and the second (Y_Step_Neg.png) taken with the new driver. The only oddity, which doesn't affect the motion but does affect power consumption, is that the signals are not initialized to high (AKA inactive state) on program startup. The signals do go high and remain there after the first step, however. The motors are energized at high level when the signal is left low.
Thank you for building this! I'll use this until your new, improved, version is available.
Tom
<<attachment: Y_Step_Neg.png>>
<<attachment: Y_Step_Pos.png>>
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