#linuxcnc-devel Logs

Jan 28 2020

#linuxcnc-devel Calendar

12:01 PM Tom_itx: pcw_mesa, i'm messing with my spartan6 demo board and ran across this error maping a quadrature encoder: https://paste.ubuntu.com/p/WYN27XjTqF/
12:05 PM Tom_itx: any idea how i can find suitable pins to eliminate the error?
12:05 PM Tom_itx: for now i used CLOCK_DEDICATED_ROUTE to get by it just to test
12:05 PM Tom_L: thanks for any input...
12:05 PM pcw_home: You are trying to use a normal input as a clock (normally a quadrature counter would not use a high speed physical clock)
12:07 PM pcw_home: you could perhaps make it work by choosing a FPGA clk pin, but its really a design issue
12:08 PM pcw_home: (that is an external dirty input like QA should never be a high speed clock)
12:08 PM Tom_L: this was just a quick test to make sure the quadrature was in fact working so i used an always@(posedge quadA )
12:08 PM Tom_L: as a trigger
12:08 PM pcw_home: for that simple test to work you would need to chose a CLK pin for A
12:09 PM Tom_L: ok
12:09 PM Tom_L: physical pin or internally mapped?
12:09 PM pcw_home: (but that's an unworkable design practically speaking)
12:09 PM Tom_L: i know
12:09 PM pcw_home: physical pin
12:09 PM Tom_L: it was quick and dirty
12:10 PM Tom_L: would i be better off triggering off the main clock?
12:11 PM pcw_home: By and large FPGA designs are synchronous state machines (common clock for all registers)
12:11 PM Tom_L: so it's not going to miss an edge
12:12 PM pcw_home: so something like a quadrature counter will sample the A input at the synchronous clock frequency (say 100 MHz or so)
12:14 PM pcw_home: perhaps do a simple digital filter and then pass the filtered A state to the actual counter (which is also synchronous)
12:18 PM Tom_L: thanks. i'll mess with this more later one. gtg now
02:38 PM andypugh: We have a keen new guy on the forum, answering nearly every question. If only he was correct more often….
02:39 PM Tom_L: :)
02:54 PM pcw_mesa: a little noise is good for evolution
02:55 PM jepler: find a way to direct his energy toward good.
06:28 PM -!- #linuxcnc-devel mode set to +v by ChanServ
06:39 PM cerna: andypugh: Don't piss him off. Even if he is wrong most of the times. Motivated people are hard to find.
06:40 PM Tom_L: a shame it has come to that
06:44 PM cerna: It was always like this. It's like teenagers learning about sex. They will get it right if the interest prevail. Then he will be useful.
07:11 PM seb_kuzminsky: not awesome: buster's buildbot is so new it doesn't talk to our ancient buildmaster
07:12 PM Tom_L: woops
07:31 PM -!- #linuxcnc-devel mode set to +v by ChanServ
08:10 PM -!- #linuxcnc-devel mode set to +v by ChanServ
08:25 PM -!- #linuxcnc-devel mode set to +v by ChanServ
09:07 PM -!- #linuxcnc-devel mode set to +v by ChanServ
09:56 PM jepler: seb_kuzminsky: mo' upgrades mo' problems. maybe you can just build a super old buildbot for buster
11:05 PM seb_kuzminsky: that's what i'm doing now - traveling backwards in time using the buildbot.deb git
11:06 PM seb_kuzminsky: while also talking with the nice ppl over on #buildbot about my woes