On 2017-10-14 00:21, andy pugh wrote:
I lost track of Machinekit a while ago. Do they have any
encoder-counting facility in the PRU?
If they have then the rest is just config. (editing text files...)
Yes, Machinekit has nice PRU encoder facility with eQEP: high-speed quadrature
+ index.
That is a strong feature of BBB. FPGA like encoder performances, without the
cost of the FPGA.
I am using it for synchronized motion on my EMCO-120P lathe with a 1024ppr
encoder and a Furaday cap.
I have wired a custom electronics to handle the differential outputs of the
encoder.
Should work to synchronize Z, even when moving the spindle manually.
My machine is WIP, so not yet tested with real chips!
See https://youtu.be/zVUMC1mdQKg?t=23m26s
PRU micro-code encoder is also available, but with lower pulse rate. I am using
it for MPG.
Also, I am using the PRU micro-code to manage the stepgen: high pulse rate can
be achieved without impact on CPU load.
Encoder electrical wiring as below:
P8.12: SPINDLE A
P8.11: SPINDLE B
P8.16: SPINDLE INDEX
Here is the portion of my hal config file:
loadrt hal_arm335xQEP encoders=eQEP0,eQEP2
# Spindle encoder
addf eqep.update servo-thread
setp eQEP2.position-scale 4096
setp eQEP2.min-speed-estimate 0.2
setp eQEP2.capture-prescaler 5 # can measure down to 50 Hz pulses / 20 rpm
setp eQEP2.counter-mode 0 # Quadrature mode
setp eQEP2.invert-B 1
net spindle-position eQEP2.position => motion.spindle-revs
net spindle-velocity eQEP2.velocity => motion.spindle-speed-in
net spindle-index-enable eQEP2.index-enable <=> motion.spindle-index-enable
Frederic
http://cnc.f1oat.org
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