Patterngen hw

patterngen

Composite video test pattern generator: RP2040 + ADV7391 encoder, PAL and NTSC. It replays the patterns of two classic Philips generators from their original ROM dumps:

• PM5644 Colour Circle (PAL-G and NTSC)
• PM5631 multi-pattern generator, all 98 patterns (PAL-G and NTSC)

plus computed test signals named SYNTH ...: multiburst, and an edges demo showing hard and band-limited luma steps, pulses and colour bars side by side.

Hardware

A 45 x 76 mm board, powered and controlled over USB-C:

• RP2040 with 16 MB flash (W25Q128JVS) holding the pattern data.
• ADV7391 encoder on a 27 MHz oscillator, fed BT.656 by the RP2040's PIO; CVBS on DAC1.
• ADA4432-1 output amplifier, 75 ohm, BNC.
• Two buttons, a status LED, test points RUN (TP1), USB_BOOT (TP2) and GND.

Getting it made

patterngen-hw/production/ has the files for JLCPCB PCB assembly: upload patterngen-hw.zip (Gerbers and drill files) as the PCB, enable assembly, and give it bom.csv (with LCSC part numbers) and positions.csv.

The BNC socket (J1) is not in the BOM; solder it yourself. Its footprint is the common right-angle PCB BNC layout, drawn for the Amphenol B6252HB-NPP3G-50. Any right-angle PCB BNC socket with this layout fits, including cheap generic ones; check the pin layout in its datasheet. A 75 ohm socket matches the cable, but a 50 ohm one works as well: the mismatch is negligible at video frequencies, and is compatible with 75 ohm cables.

Case

Print patterngen-box/patterngen-case-bottom.stl and patterngen-case-top.stl. The board is held by 4 x M3x12 socket head screws from below, screwed into the top half.

Firmware

Building and flashing

PlatformIO with the maxgerhardt/platform-raspberrypi platform and framework = picosdk:

cd patterngen-fw
pio run

For the first flash, hold TP2 (USB_BOOT) to GND while powering up and copy .pio/build/patterngen/firmware.uf2 to the drive that appears. Later updates can use picotool or pio run -t upload.

Controls

• Button 1: next favourite (PM5644 Colour Circle, 15 PM5631 patterns, multiburst; list in src/patterns.c).
• Button 2: toggle PAL / NTSC.
• LED: slow blink = running, fast blink = ADV7391 does not answer on I2C.

Serial commands (USB CDC)

Bring-up

1. Run status. "ADV7391 NOT FOUND": check I2C (GPIO2/3), ~RESET (GPIO0) and the encoder supplies.
2. bars on shows the encoder's internal colour bars, without the pixel bus.
3. With a pattern, late and underruns in status must stay at 0. Underruns show as green streaks on black, tearing or unstable sync.
4. Vectorscope: colour bars (PM5631 2, 11, 12) in the targets; burst at +-135 degrees (PAL) or 180 (NTSC); chroma saw/staircase patterns (PM5631 85, 86, 88, 89) on their stated angles.

Video engine

The ADV7391 runs in SD slave mode with embedded EAV/SAV timing (BT.656, 8-bit 4:2:2), with the 16x oversampling PLL on.

Chroma is trimmed with the encoder's colour scale registers (adv7391_configure()): Cb x 1.039 (0x9E = 0x85), Cr x 1.047 (0x9F = 0x86), Y x 1.0 (0x9D = 0x80), 0x9C = 0x00, then enabled by 0x87 = 0x01. Write the scales before the enable: enabling with a scale still at 0 blanks the picture. Calibrated on a vectorscope in PAL only; another board may need different values.

The PIO program (src/bt656.pio) follows the 27 MHz clock on GPIO1, outputting one byte after each rising edge; the encoder latches it on the next. The RP2040 itself runs at 216 MHz, not locked to it. The data pins are bit-reversed (P7..P0 on GPIO4..11), which the PIO corrects.

src/video.c plays a ring of 8 complete BT.656 lines to the PIO with two chained DMA channels. Core 1 refills each slot 7 lines ahead, reading the active part from flash in one SSI burst per line (27 us). XIP is too slow for this and unavailable during a burst, so the firmware runs from SRAM (copy_to_ram) and only the pattern data stays in flash.

Pattern data

patterngen-fw/data/*.bin are generated from the ROM dumps in patterngen-fw/rom/ (described in patterngen-fw/rom/README.md) and embedded by src/blobs.S. From patterngen-fw/:

python3 tools/pm5644_convert.py rom/PM5644G00 rom/PM5644M00 -o data
python3 tools/pm5631_convert.py rom/PM5631G rom/PM5631M -o data
python3 tools/synth_convert.py -o data

--preview also writes PNG images (data/preview/). After changing the blobs, run pio run -t clean before building.

Blob format (tools/pmblob.py, little-endian)

Credits

This project builds on the Philips test equipment preservation work of inaxeon:

• PTV_Preservation: the PM5644 and PM5631 ROM dumps in patterngen-fw/rom/, and the GAL fuse map dumps, schematics and service manuals used to work out how the generators read them.
• PhilipsPatternRom: the reverse-engineered PM5644 ROM format, which tools/pm5644_convert.py re-implements in Python.

License

Copyright (c) 2026 Pavel Sorejs mail@sorejs.eu

• Firmware, tools and documentation: BSD 2-Clause.
• Hardware (patterngen-hw/) and case (patterngen-box/): CERN-OHL-P v2, the permissive variant; see the LICENSE file in each folder.
• Not covered: the Philips ROM dumps in patterngen-fw/rom/ and the pattern data generated from them (patterngen-fw/data/pm56*.bin and their previews). They are Philips' work and are included for preservation.