Code for the xerox 820 to digital video project

CircuitPython_Feather_DVI_Xerox_820/code.py

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+# SPDX-FileCopyrightText: 2024 Jeff Epler for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+
+import array
+
+import ulab
+import rp2pio
+import board
+import adafruit_pioasm
+import picodvi
+import displayio
+
+vdata = board.D9 # Followed by hsync on D10 & vsync on D11
+pixel_sync_out = board.D5
+pixel_frequency = 10_694_250 # oddly specific
+clocks_per_pixel = 10
+fine_pixel = 0
+
+displayio.release_displays()
+
+dvi_pins = dict(
+ clk_dp=board.CKP,
+ clk_dn=board.CKN,
+ red_dp=board.D0P,
+ red_dn=board.D0N,
+ green_dp=board.D1P,
+ green_dn=board.D1N,
+ blue_dp=board.D2P,
+ blue_dn=board.D2N,
+)
+
+try:
+ dvi = picodvi.Framebuffer(640, 240, **dvi_pins, color_depth=1)
+except ValueError:
+ print(
+ "Note: This version of CircuitPython does not support 640x240\n."
+ "Display will be compressed vertically."
+ )
+ displayio.release_displays()
+ dvi = picodvi.Framebuffer(640, 480, **dvi_pins, color_depth=1)
+
+# Clear the display
+ulab.numpy.frombuffer(dvi, dtype=ulab.numpy.uint8)[:] = 0
+
+active_lines = 240
+blanking_lines = 18
+active_pixels = 640
+blanking_pixels = 58
+total_lines = active_lines + blanking_lines
+
+
+def instruction_gen():
+ yield total_lines - 2
+ for _ in range(blanking_lines):
+ yield from (1, 0) # 0 active pixels is special-cased
+ for _ in range(active_lines):
+ yield from (blanking_pixels - 1, active_pixels - 1)
+
+
+instruction = array.array("L", instruction_gen())
+print(instruction)
+
+jmp_0 = adafruit_pioasm.Program("jmp 0")
+
+program = adafruit_pioasm.Program(
+ f"""
+.side_set 1
+
+ .wrap_target
+ out y, 32 ; get total line count
+ wait 0, pin 2
+ wait 1, pin 2 ; wait for vsync
+
+wait_line_inactive:
+ out x, 32 ; get total line count
+ wait 0, pin 1
+ wait 1, pin 1; wait for hsync
+
+wait_line_active:
+ nop [{clocks_per_pixel-2}]
+ jmp x--, wait_line_active ; count off non-active pixels
+
+ out x, 32 [{fine_pixel}] ; get line active pixels & perform fine pixel adjust
+ jmp !x, wait_line_inactive ; no pixels this line, wait next hsync
+
+capture_active_pixels:
+ in pins, 1 side 1
+ jmp x--, capture_active_pixels [{clocks_per_pixel-2}] ; more pixels
+ jmp y--, wait_line_inactive ; more lines?
+ .wrap
+"""
+)
+
+pio = rp2pio.StateMachine(
+ program.assembled,
+ frequency=pixel_frequency * clocks_per_pixel,
+ first_in_pin=vdata,
+ in_pin_count=3,
+ # in_pin_pull_up=True,
+ first_sideset_pin=pixel_sync_out,
+ auto_pull=True,
+ pull_threshold=32,
+ auto_push=True,
+ push_threshold=32,
+ offset=0,
+ **program.pio_kwargs,
+)
+
+words_per_row = 640 // 32
+first_row = (dvi.height - 240) // 2 # adjust text to center if in 640x480 mode
+buf = memoryview(dvi).cast("L")[
+ first_row * words_per_row : (first_row + active_lines) * words_per_row
+]
+assert len(buf) == 4800 # Check that the right amount will be transferred
+
+b = array.array("L", [0])
+
+while True:
+ pio.run(jmp_0.assembled)
+ pio.clear_rxfifo()
+ pio.write_readinto(instruction, buf)