Details

PICO9918

A drop-in replacement for a classic TMS9918A VDP using a Raspberry Pi Pico.

The TMS9918A emulation is handled by my vrEmuTms9918 library which is included as a submodule here.

Supported devices

This is a list of devices the PICO9918 has been tested and confirmed to work on.

Texas Instruments TI-99/4A (NTSC and PAL)
Texas Instruments TI-99/4QI
CBS ColecoVision (NTSC and PAL)
Powertran Cortex
Casio PV-7 (MSX)
NABU Personal Computer

Homebrews:

Troy Schrapel's HBC-56
Stuart Connor's TM990

If you have tested the PICO9918 on any other device, please let me know and I'll happily update this list. :)

Unsupported devices

So far, there aren't any.

Purchasing options

Fully assembled and tested PICO9918 v1.0s are available on my Tindie store:

Also (more convenient for North America)

Hardware

There are two main variants of the hardware.

v1.0 (formerly v0.4)

PICO9918 v1.0 is the single board version which doesn't require a piggy-backed Pi Pico. It is in the process of being manufactured now and is based on v0.4 seen below:

Once I have tested v1.0 and made it available, I will publish the schematics and gerbers for this version.

v0.3

v0.3 schematic and gerber available now. This revision has been tested on my two TI-99/4As (PAL and NTSC) and my HBC-56 and is fully functional, however it is not representative of the final PCB design which will include the RP2040 directly on the PCB.

PCB v0.3 Notes

There are a number of 0Ohm resistors (jumpers). You may need to omit the RST resistor. On some machines, the extra time is required to bootstrap the Pico. This will be changed to a soft reset on v0.4.

Raspberry Pi Pico Module

Note: Due to GROMCLK and CPUCLK using GPIO23 and GPIO29, a genuine Raspberry Pi Pico can't be used. v0.3 of the PCB is designed for the DWEII? RP2040 USB-C module which exposes these additional GPIOs. A future pico9918 revision will do without an external RP2040 board and use the RP2040 directly.

Purchase links:

I could reduce the VGA bit depth to 9-bit or 10-bit to allow the use of a genuine Raspberry Pi Pico board, but given the longer-term plan is to use the RP2040 directly, I've decided to go this way for the prototype.

Firmware

If you're not interested in building the firmware yourself, you'll find the latest firmware in the Releases.

To install, just hold the 'BOOTSEL' (or 'BOOT') button while plugging the Pico into a PC, then drag the pico9918.uf2 file on to the new USB drive which should have the volume label RPI-RP2. The Pico will restart (and disconnect) automatically.

Development environment

To set up your development environment for the Raspberry Pi Pico, follow the Raspberry Pi C/C++ SDK Setup instructions.

Windows

For Windows users, there is a pre-packaged installer provided by the Raspberry Pi Foundation: https://github.com/raspberrypi/pico-setup-windows/releases/. Once installed, just open the pre-configured "Pico - Visual Studio Code" from your start menu.

The build system expects python3 to be available. If you have installed Python 3 outside of the Microsoft Store, you may need to alias your Python executable.

You can do this from an elevated (Administator) command prompt in your python directory e.g. C:\Program Files\Python310\ by creating a symlink with the command: mklink python3.exe python.exe.

Discussion

For all the latest news and discussion on the PICO9918, you can follow this AtariAge thread

Videos

Initial "raw" videos recorded in the moments following the first boot on my TI-99/4A.

These videos are showing the v0.2 hardware with an external Pi Pico providing the required GROMCLK signal to the TI-99. This signal has been added to v0.3. I'm still waiting on v0.3 boards to arrive.

It freaking works!

Don't...

Project Logs

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PICO9918 no-cut mode prototype for the TI-99/4A

Troy Schrapel • 11/04/2024 at 23:04 • 0 comments

Received my prototype PICO9918 no-cut mod PCBs for the TI-99 today. Places VGA and audio connectors externally via the DIN socket hole. Still need to design an enclosure for it. Will try one out in the next few days and report back.

PICO9918 RP2040 vs RP2350 vs F18A performance testing

Troy Schrapel • 10/23/2024 at 06:50 • 0 comments

Some initial GPU performance tests of the PICO9918 powered by an RP2040 vs an RP2350 version vs an F18A MK1. Very interesting results.

Pimoroni PGA2350 powered PICO9918 prototype (say that 5 times)

Troy Schrapel • 10/18/2024 at 04:33 • 2 comments

I have no immediate plans to switch to an RP2350-powered PICO9918, but I thought I'd design some prototype boards utilizing the awesome Pimoroni PGA2350 for testing purposes.

Initial tests show it is somewhat faster which will come in handy for the F18A compatibility mode but won't have any impact on the standard TMS9918A modes.

Extra I/Os could come in handy for configuration jumpers too.

PICO9918 showing off F18A compatibility

Troy Schrapel • 09/25/2024 at 12:43 • 0 comments

The RP2040 powered TMS9918A VDP has another trick up its sleeve. F18A compatibility:

Also, the list of compatible devices is still growing. The PICO9918 has now been tested on the following machines:

Texas Instruments TI-99/4A (NTSC and PAL)
Texas Instruments TI-99/4QI
ColecoVision (NTSC and PAL)
Coleco ADAM (NTSC)
MSX
- Casio PV-7
- Toshiba HX-21
NABU Personal Computer
Powertran Cortex
Sega SC-3000
Sord M5
Tomy Pyuuta

PICO9918 tested on NABU and MSX

Troy Schrapel • 09/10/2024 at 01:25 • 0 comments

The supported devices list is getting longer...

The PICO9918 is now confirmed to work on the following systems:

Texas Instruments TI-99/4A (NTSC and PAL)
Texas Instruments TI-99/4QI
CBS ColecoVision (NTSC and PAL)
Powertran Cortex
Casio PV-7 (MSX)
NABU Personal Computer

F18A mode for the PICO9918 coming soon?

Troy Schrapel • 09/08/2024 at 11:41 • 0 comments

Significant progress has been made towards F18A support on the PICO9918. Check out this short video showing it off to varying degrees of success.

PICO9918 now available on Tindie

Troy Schrapel • 08/21/2024 at 05:32 • 0 comments

The first batch is now available on Tindie. For those in US/Canada, they will soon be available at arcadeshopper.com

PICO9918 1 PICO9918 from Troy Schrapel on Tindie

Partially assembled v1.0 boards have arrived

Troy Schrapel • 08/19/2024 at 15:16 • 0 comments

They have arrived! My partially assembled PICO9918 v1.0 boards are here. Of course, I had to complete one to try them out... Success!

The first v1.0 board works perfectly :) Now, it will take some time for me to complete the assembly of all 50 boards and their VGA dongles, but once I do (or more likely before all 50 are done). I'll put them up on my Tindie store.

First batch of PICO9918 v1.0 boards ordered

Troy Schrapel • 08/03/2024 at 03:44 • 0 comments

Just ordered 50x mostly-assembled PICO9918 boards. Here's some pics of my hand-built examples so far.

Hoping the PCBA shop will make producing these bad boys far more painless than they currently are :D. So far, I've managed to hand-build a whole five (5) of the v0.4 boards and one of those is dead :D :( . They take a lot of time to assemble, then test, diagnose and fix the various reflow issues which crop up. Looking forward to not having to do that. Or at less a lot less of it.

First PICO9918 v0.4 PCB working

Troy Schrapel • 07/20/2024 at 13:17 • 0 comments

Apologies in advance for the vertical video.

Works great! Got the blinkenlights. Much lower profile than v0.3. Now to build a few more...

Discussions

sabasonia6363 wrote 08/21/2024 at 05:49

This is an impressive project! The PICO9918 is shaping up to be a fantastic drop-in replacement for the classic TMS9918A VDP. It’s exciting to see the prototype running smoothly on the TI-99/4A. Your detailed updates and plans for future revisions are very informative.

For more information, use this calculator. Keep up the great work!

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PICO9918

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PICO9918