Using Adafruit Macropad as LinuxCNC Control Pendant

Update, 2021-09-25: For compatibility with CircuitPython 7.0.0

CircuitPython recently gained the power to have custom USB descriptors. With these, we can define a USB HID device that will work with LinuxCNC's hal_input.

For instance, the Adafruit Macropad has a (very coarse, just 20 detents/revolution) encoder, 12 keyswitch positions, and an OLED screen.

The two pieces of software below, when placed in the CIRCUITPY drive as boot.py and code.py configure it for use with hal_input, using a halcmd line similar to loadusr -W hal_input Macropad. I haven't actually done the work of hooking it all the way up to Touchy yet, but it causes all the buttons & the encoder to appear in halcmd show pin.

This is just the device I picked first; there's nothing to prevent you from hooking up more exotic things like voltage/temperature monitors through added CircuitPython code. Addition of output reports for status indicators is left for the motivated reader.

Running with python3? You may need a very recently contributed patch to make hal_input work again.

	import usb_hid

	PENDANT_DESCRIPTOR = bytes((
	0x05, 0x01, # USAGE_PAGE (Generic Desktop)
	0x09, 0x02, # USAGE (Mouse)
	0xa1, 0x01, # COLLECTION (Application)
	0x85, 0x04, # Report ID (4),
	0x09, 0x01, # USAGE (Pointer)
	0xa1, 0x00, # COLLECTION (Physical)
	0x05, 0x09, # USAGE_PAGE (Button)
	0x19, 0x01, # USAGE_MINIMUM (Button 1)
	0x29, 0x0d, # USAGE_MAXIMUM (Button 13)
	0x15, 0x00, # LOGICAL_MINIMUM (0)
	0x25, 0x01, # LOGICAL_MAXIMUM (1)
	0x95, 0x0d, # REPORT_COUNT (13)
	0x75, 0x01, # REPORT_SIZE (1)
	0x81, 0x02, # INPUT (Data,Var,Abs)
	0x95, 0x01, # REPORT_COUNT (3)
	0x75, 0x03, # REPORT_SIZE (1)
	0x81, 0x03, # INPUT (Cnst,Var,Abs)
	0x05, 0x01, # USAGE_PAGE (Generic Desktop)
	0x09, 0x30, # USAGE (X)
	0x15, 0x81, # LOGICAL_MINIMUM (-127)
	0x25, 0x7f, # LOGICAL_MAXIMUM (127)
	0x75, 0x08, # REPORT_SIZE (8)
	0x95, 0x02, # REPORT_COUNT (1)
	0x81, 0x06, # INPUT (Data,Var,Rel)
	0xc0, # END_COLLECTION
	0xc0 # END_COLLECTION
	))

	pendant = usb_hid.Device(
	report_descriptor=PENDANT_DESCRIPTOR,
	usage_page=0x01, # Generic Desktop Control
	usage=0x05, # Gamepad
	in_report_lengths=(3,), # This gamepad sends 3 bytes in its report.
	out_report_lengths=(0,), # It does not receive any reports.
	report_ids=(4,), # It does not use report IDs
	)



	usb_hid.enable([
	pendant
	]
	)

view raw boot.py hosted with ❤ by GitHub

	# pylint: disable=import-error, unused-import, too-few-public-methods

	import displayio
	import terminalio
	from adafruit_display_shapes.rect import Rect
	from adafruit_display_text import label
	from adafruit_macropad import MacroPad
	import rainbowio
	import usb_hid
	import time

	# INITIALIZATION -----------------------

	macropad = MacroPad()
	macropad.display.auto_refresh = False
	macropad.pixels.auto_write = False

	# Set up displayio group with all the labels
	group = displayio.Group()
	for key_index in range(12):
	x = key_index % 3
	y = key_index // 3
	group.append(label.Label(terminalio.FONT, text='', color=0xFFFFFF,
	anchored_position=((macropad.display.width - 1) * x / 3,
	macropad.display.height - 1 -
	(3 - y) * 12),
	anchor_point=(0.0, 1.0)))
	group.append(Rect(0, 0, macropad.display.width, 12, fill=0xFFFFFF))
	group.append(label.Label(terminalio.FONT, text='', color=0x000000,
	anchored_position=(macropad.display.width//2, -2),
	anchor_point=(0.5, 0.0)))
	macropad.display.show(group)

	group[0].text = "X"
	group[1].text = "Y"
	group[2].text = "Z"

	group[3].text = ".1"
	group[4].text = ".01"
	group[5].text = ".001"

	group[6].text = "H. All"
	group[7].text = "Run"
	group[8].text = "Pause"

	group[9].text = "Abort"
	group[10].text = "Power"
	group[11].text = "E-Stop"

	group[13].text = "LinuxCNC Pendant"

	last_position = macropad.encoder
	last_encoder_switch = macropad.encoder_switch_debounced.pressed

	macropad.display.refresh()

	dev = usb_hid.devices[-1]

	# MAIN LOOP ----------------------------

	last_report = None
	report = bytearray(3)

	def let_button(key_number, pressed):
	idx = key_number // 8
	bit = 1 << (key_number & 7)
	if pressed:
	report[idx] \|= bit
	else:
	report[idx] &= ~bit

	while True:
	# Read encoder position. If it's changed, switch apps.
	position = macropad.encoder
	report[2] = (position - last_position) & 0xff
	last_position = position

	let_button(12, macropad.encoder_switch)

	while event := macropad.keys.events.get():
	let_button(event.key_number, event.pressed)

	if report != last_report:
	print("sending report", report)
	try:
	dev.send_report(report)
	last_report = report[:]
	except OSError as e:
	print(e)
	time.sleep(.01)

view raw code.py hosted with ❤ by GitHub

Using Adafruit Macropad as LinuxCNC Control Pendant

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