cnc_pendant

Connect an XHC WHB04B pendant to a GRBL-based CNC controller using a RaspberryPi Zero

TODO

• Clean this up and add some text about how all this is supposed to work
• Document the code
• Add tests
• Provide pictures and documentation for the HW

Notes

• Button Interpretation:

  • Reset: issue a soft reset to the Controller
    • using '^X' realtime command
  • Stop: stop everything and leave it in position
    • using '!' realtime command
  • Start/Pause: toggle between cycle start and resume
    • using '~' realtime command
  • Feed+/-: adjust feed rate while program is running
  • Spindle+/-: adjust spindle speed while program is running
  • M-Home: stop and home all three axes in machine coordinate space
    • set to machine coordinate space
  • Safe-Z: retract spindle to top of Z axis travel (home Z axis only)
  • W-Home: stop and home all three axes in workpiece coordinate space
  • S-on/off: toggle spindle on/off
  • Probe-Z: run probing cycle
  • Continuous: set into continuous movement mode
    • selected axis will move in direction of jog wheel movement (i.e., cw or ccw)
    • movement will stop whenever wheel movement stops
    • movement is done at the rate given by the increment knob setting
      • i.e., a percentage of max movement rate
    • movement is independent of speed at which the jog wheel is rotated
  • Step: set into step movement mode
    • selected axis will move in direction of jog wheel movement
    • movement is in increments given by the increment knob setting
  • Macro-[1-11]: defined by yaml in button config file

• Adding more increments to the incr knob in step mode: 10.0, 50.0, 100.0

  • ignoring/not implementing the 'Lead' setting

• Reset

  • Pendant comes out of power-up in RESET mode
    • it remembers the last coordinate line values it was given and displays "RESET"
      • remains in this state until overwritten
    • comes up with selected axis as given by axis knob
      • could have changed during power down
  • can change coordinate lines on the display while in reset mode
  • reset sequence on power-up
    • set RESET flag
    • wait for motion mode button to be pressed
      • ignore all other inputs
    • clear RESET flag
  • the pendant remains in the previous coordinate space at startup
    • must get the current coordinates and space from the Controller and update the display on reset
  • pendant emits current state of knobs (and buttons/jog wheel) on power-up
    • not doing anything with it right now
  • sometimes emits a null data packet -- i.e., all zeros (key1, key2, incr, axis, jog)
    • sometimes first thing after powerup is a null packet
    • pendant looks like it continues emitting packets until it is reset

• Display

  • pendant automatically displays the value of the axis knob with an asterix next to a coordinate line
    • host is not able to set the selection marker
  • top display line is the status line RF bars icon, battery level icon, and mode word
    • mode word starts as "RESET" until motion mode mode is set
  • after motion mode is selected, the mode word becomes either "CONT" or "STP"
    • the value following the mode word is dependent on the mode
      • for "STP" the value is a floating point number
      • for "CONT" the value is a percentage
  • the display format is specific to the motion mode
    • e.g., "STP: 1.0", "CONT: 30%"
    • both MPG and PCT motion modes display "XX%", where 'XX' is given by the incr knob setting
      • no text associated with these modes -- just 'XX%'
  • if axis knob is in "off" state, can't update the display
    • don't send display packets if that's the case -- drop commands and log warnings
    • if power on with axis "off", emits axis off (0x06) and state of incr knob
      • could suppress this in this object
    • doesn't automatically update the display if axis is Off
  • the display automatically updates CONT/STEP mode values based on knob positions
  • the coordinate lines display the current machine position
    • X, Y, Z or A, B, C coordinates if in Machine coordinate system
    • X1, Y1, Z1 or A1, B1, C1 coordinates if in Work coordinate system
  • the currently selected coordinate (i.e., the one where motion will occur) is (automatically) indicated on the display with an asterix

• Input

  • this object emits the (lightly parsed) basic events from the pendant
    • puts them into an internal queue, provide method to pull from this input queue
    • the action logic (e.g., in the main code body) will pull from this queue via methods
    • an input thread handles device events, does the pre-processing, and queues the output
  • outputs from the pendant include: key1, key2, axis, incr, and jog
    • any number of these can be null in a packet
    • there's also a header, seed, and checksum in each packet
      • these values are not currently being used by this code
      • the header is checked but the checksum is currently not
      • have to figure out what the seed does and how the checksum works
  • button-down events have a key value, then button up events are signified by 0x0 value
    • e.g., pressing a single key results in reports with key1=0x??, then key1=0x00 when it is released
    • e.g., button down will give the keyName, button up returns 'Noop'
  • key1 is the first key pressed, key2 is the second key pressed while key1 is held
    • this means any key can be a modifier -- but only "Fn" is so marked
  • key values are between 0x00 (nothing pressed) and 0x10
    • 0x01 starts in upper left ("Reset") and raster left-right, top-down
    • "Continuous" = 0x0e, "Step" = 0x0f, last key is "Macro-10" = 0x10
  • when the axis knob is in the "off" position, no jog deltas are sent
    • in this case, axis == 0x06 and jog == 0x00 (there's not axis to apply the jog to)
  • all button and knob values are small integers -- except incr "Lead" == 155
  • the pendent emits NOP packets when the axis knob is not set to "Off" and the jog wheel is not moving
    • the pendent continuously sends a jog value of 0
  • the input tuple contains:
    • the (possibly empty) name of a pressed key,
    • the current setting of the axis knob, the current setting of the increment knob,
    • and the jog wheel delta
  • if no key was pressed, then the key name will be None.
  • if the axis knob is set to "Off" a None is given for the axis value,
    • otherwise, the axis character is given as a string -- e.g, "X", or "A".
  • the increment knob returns either:
    • a float (that corresponds to the increment to be moved by with each click of the jog wheel when in "STEP" mode)
    • or an integer (that corresponds to the percentage of the maximum speed at which it can move).
  • reports current axis and incr knob settings
    • axis: 0x06="off"
    • incr: 0x0e=0.001/2%, 0x0d=0.02/5% ...

• notes

  • always have to click some button after power-on of Pendant
    • otherwise, don't know when you just turned on the Pendant
    • assume that the app is always running and the Pendant gets turned on/off at random times
      • also, if the Pendant is on when the app starts, then need to hit the button again
    • use Fn(RESET) to get Pendant out of reset mode
  • use Fn(STOP) to exit app
  • need to interrogate the Controller to get the current values for the Coordinates
    • just do this by periodically asking the Controller for status ('?')
    • status inputs are demuxed onto another channel
  • the -4 pendant only has four values (0x11-0x14), other two values for the -6
  • this application should interpret the final three positions of the incr knob as: 10, 50, 100?
  • the input from the pendant and the pendant's display are logically independent
    • it may take some time for the controller to receive inputs from the pendant and send back results that then are sent to the pendant's display
    • everything should converge to a consistent state quickly
  • other controllers have MPG and CONT/STEP buttons
    • mine has CONT and STEP buttons
      • this means that it only understands two modes
      • this is why I've never seen "MPG" or "PCT" displays
  • doesn't update 'F:<>' display when in STEP mode, does in CONT mode
  • pendant remembers the coordinates and other state between power cycles
    • but comes up with RESET flag set -- must clear it to go on

• install udev rules for RF dongle and reload udevd

  • sudo cp ./99-xhc-whb04b-4.rules /etc/udev/rules.d/
  • sudo udevadm control --reload-rules
  • sudo udevadm trigger

• info on the xhc-whb04b-6

  • https://github.com/machinekit/machinekit/blob/master/src/hal/user_comps/xhc-whb04b-6/README.md