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 Startup screen with Pico9918, still image made with VGA framegrabber and an aligned resolution of 720x480. The logo appears only once after power up, and dissolves after some seconds. The overshoots in front of the black pixels are made by the digitizer of the framgrabber - they don't appear on the monitor! And: yes, I know that the firmware is outdated - it's in the queue.... |
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When in 2025 you were searching for new AND available hardware for the TI-99/4A, you may not always be successful... A lot of highly interesting projects began, or already ended around the millennium, and those which started then, have been available until around 10 years ago, and are surfacing currently either never or very seldom as used items, but often for ridiculous prices (there are exceptions from this rule, but you need a lot of patience) - e.g. the NanoPEB, the CF7 variant, or the F18A VDP and so on. So it was a pleasant surprise to me, to find an active source for a very interesting VDP replacement, namely the Pico9918 by Troy Schrapel from Down Under, that is not only still in production, but - best of all - still is developed further! In short, this is a Raspberry Pi Pico based upon the Broadcom 2040 Chip, which simulates a TMSS9918A/9929A VDP AND an F18A completely in software, and was initially planned to be a replacement for the TMS9918A, which drove more home computers and game consoles, the average TI-99/4A user may usually be aware of. With some additional hardware for the VGA video output (all on this small PCB!), it produces an upscaled 640x480 image at 60 Hz frame reate, that is worth looking! | |||
The hardware | |||
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The Pico9918 directly replaces the TMS9918/9929 in its socket, and is connected by a tiny ribbon cable to a VGA connector, which you can place at a suitable spot in your console - that's all! The upper left image shows 5 coloured wires of the TMS-RGB, which surely do not work with the Pico, since it makes no sense to additionally generate composite or differential video besides the VGA output. If you like, you may remove the DRAMs of the old VDP, which saves you some milliamps - the Pi uses its own RAM, of which he has plenty... |
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80 colums? | |||
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Sure - this is possible, when using software which can handle it. It also provides the 'classical forth screen' with 64 columns, but to really use it, the TIPI telnet implementation must provide a readable font - making pictures of this mess was out of the question... For more screenshots look at the TIPI pages on this website. |  | ||
Updates | |||
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For sure the Pico can receive software updates to update it should the need arise.
The method is the same as with all micro controllers of this kind, namely by an UF2 file, which may require you to remove the Pico (up to hardware 1.2),
or you considered this when mounting it, and did add an external USB connector and added an additional BOOT button in a place where you can reach it
without dismantling the console - but to leave it mounted you will have to use hardware version 1.3 and up. If it would be possible to emulate a Yamaha 9935 VDP with a 2040, or if this requires a Pico 2 based on the 2350, has - at least to my knowledge - not yet been settled. But since the current firmware (1.0 and above) has full F18 support... would you need it? | |||
Done yet? Nope... | |||
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At the moment, I'm lacking a good idea how to keep the Pico IN the console, and to get the signals (preferrably with sound) OUT of the console. The No-Cut Breakout-Board, as suggested by Troy, which you can buy separately at Tindie, seems to be dangerously thin at the point where it comes out of the console, and is - imho - easy to break, and nobody will ever use the DIN connector once the Pico is in, nor does the TI output stereo sound. I'm planning to keep the DIN connector, but only to be used with an adapter cable, which gives you a VGA connector and a sound out via cinch at its other end, so nobody will notice the change. This will require a 10cm 12 pin FFC cable plus a suitable adapter with soldering pads. The existing lines to the connector will be cut completely, and connected to the adapter plus audio. For european PAL consoles, this would work, since we need those signals:
For the US consoles with their 5 pins only, there is no way to pass the audio - well, then we must make the console sound - new project! | |||
| Contact: {anyname}@{use_the_url}.net |
All pictures on this whole website were made by myself. Should you find them elsewhere, they're stolen from here! |
Last update: 2026-01-07 CW |
