In this video I show how I laid out a new 40 pin version of the One ROM, which is intended to support 16-bit systems like the Amiga, using the B variant of the Raspberry Pi RP2350/RP2354. I cover:

  • the 27C400 ROM chip often used in these 16-bit systems
  • the constraints on the layout due to my firmware design
  • laying out the PCB in KiCad, starting from a copy of the 28 pin One ROM Fire layout

🔗 Links

One ROM website: https://onerom.org/
16-bit firmware design: https://github.com/piersfinlayson/one-rom/discussions/69#discussioncomment-15436012
An alternate design by a subscriber: https://github.com/going-digital/A600ROM/tree/main/hardware

Buy One ROMs

Keep an eye on my online store if you want to buy One ROMs when they are available:

https://www.packom.net/product/one-rom/

If you sell a version of One ROM, let me know so I can publicise it on youtube and at https://onerom.org/

⏰ Timestamps

00:00:00 Introduction
00:03:20 16-bit ROM
00:06:24 Schematic differences from 28 pin
00:07:52 Layout constraints
00:14:00 Starting PCB layout from 28 pin
00:20:10 Ripping the 28 pin design apart
00:22:20 Placing new components
00:26:12 Starting to route traces
00:28:48 Assembly constraints
00:29:57 Routing 16-bit data bus
00:42:06 Voltage rails
00:45:11 Address lines routed
00:46:22 Bypass capacitors
00:49:27 Crystal oscillator
00:50:19 More bypass capacitors
00:53:42 VREF circuitry
01:02:31 Flash chip laid out
01:06:46 Adding more features
01:17:53 Layout complete
01:20:54 Final thoughts

Video content copyright (c) 2026 piers.rocks Limited. All rights reserved.

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