Gigatron ASIC and the Gametron Handheld

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bmwtcu
Posts: 122
Joined: 01 Nov 2018, 12:02

Re: Gigatron ASIC and the Gametron Handheld

Post by bmwtcu »

I got a good laugh out of this. Efabless (who runs the OpenMPW shuttles Google is paying for) just launched a kickstarter based on silicon from the very same 130nm ASIC process, and they basically made a (very small) open source embedded FPGA. It's too small to fit a Gigatron and would need 2 orders of magnitude more SRAM, but it's commendable that they've come up with a process whereby anyone versed in Verilog can turn that idea in their head into real silicon for <$10k NRE cost.

https://www.hackster.io/news/efabless-c ... a9e5a20326

https://groupgets.com/pre_launch_campai ... chipignite
bmwtcu
Posts: 122
Joined: 01 Nov 2018, 12:02

Re: Gigatron ASIC and the Gametron Handheld

Post by bmwtcu »

https://www.youtube.com/watch?v=oD6P2cYZCfo

#JLCPCB
Thanks again to JLCPCB for their quick turnaround time. All my PCB designs you see in the Gametron playlist were ordered through them. As always, the boards are manufactured to a high quality, and I am always able to quickly build up my prototype to test with no concerns about PCB manufacturing issues.

I started on a board design right after posting my last video on Feb 5th 2022. I didn't think I would get to a new video so soon, but JLCPCB got the board to me in record time. I ordered 5 boards on Feb 18th 2022 for USD$2 and about USD $4 in shipping. I received the order on March 5th 2022 despite choosing the cheapest shipping option and the usual Chinese New Year slowdown experienced with many other companies I deal with. With the low cost and quick turnaround time from JLCPCB, I really don't see a need to waste time painstakingly wiring up components on a breadboard or DIYing my own boards.

Gametron playlist -https://www.youtube.com/playlist?list=P ... qG0CLZiLjt

New PCB derived from my Gigatron FPGA Bartop Arcade board (see last video in playlist). This is the Gigatron TTL design with a LGT8F328P 3.3V Arduino Nano based Pluggy Reloaded built in. SD card reader on the PCB operates natively off 3.3V as well. I had to strip out EEPROM support because the LGT8F328P doesn't have real EEPROM. Board also has a Raspberry Pi pinout 40-pin header, but I'm still hunting down an ideal display. I had hopes for a Waveshare 3.5" DPI TFT, but once again was foiled by the lack of good LCD documentation. If anyone has good recommendations for a native 640x480 LCD display that can accept a 25MHz pixel clock, please let me know. I need to investigate the weird flashing when the menu comes up. I've used the same monitor in the past for other videos without seeing this, so this might be timing related. Also note starting from 1:22 how I get 6 of the same tile in a row. Weird... The video cuts out suddenly at the end because my power bank couldn't detect enough load to keep it turned on. This should go away once the LCD display load comes into the picture. Long term goal is to figure out how to integrate the RAM & SPI Expander and load the SD Card directly from the FPGA to eliminate the LGT8F328P.

Front view
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Rear view - Yes, I needed a bodge wire... I forgot that I was trying to run everything off 3.3V and wired the Arduino Nano up to 5V.
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Sneak peek - Tang Nano 9K board. "Can it Gigatron?™"
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at67
Posts: 486
Joined: 14 May 2018, 08:29

Re: Gigatron ASIC and the Gametron Handheld

Post by at67 »

Very cool stuff, you just finally need to find a well documented, reliable and suppliable display...good luck :/
bmwtcu
Posts: 122
Joined: 01 Nov 2018, 12:02

Re: Gigatron ASIC and the Gametron Handheld

Post by bmwtcu »

https://www.youtube.com/watch?v=G1rcSN7yz0w

Gametron playlist - https://www.youtube.com/playlist?list=P ... qG0CLZiLjt

When life gives you component shortages, you start designing with parts you've been hoarding for the last 2 decades! Board has jumpers to select 4/6/8-bit audio DAC (needs accompanying FPGA image change), built-in 3.3V Pluggy Reloaded, hooks to enable further experimentation with SPI/RAM expander, but most importantly I can deal with full 64kx16 ROMs, and in fact can use DIP switches to change ROMs. I didn't use the ~2kB of BlockRAM on the Spartan 2 FPGA, so I might even be able to implement the Video Repeater as well if I have enough resources left over. Got the Strataflash working, but I have to remove power before switching ROMs otherwise the flash could get corrupted, and become a real pain in the butt to swap out (ask me how I know).
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bmwtcu
Posts: 122
Joined: 01 Nov 2018, 12:02

Re: Gigatron ASIC and the Gametron Handheld

Post by bmwtcu »

Just to document the month long effort before I disassemble it for parts. This was my initial attempt at prototyping with the Spartan 2 FPGA. (The SRAM has already been salvaged, and was probably why the proto never worked.) I only verified the proto as far as reading instructions from the OTP EPROM before I gave up debugging the mass of wires and whipped up the protoboard above in KiCad over a Sunday afternoon. I ordered up 5 boards for ~$10 shipped back to me in ~2 weeks and pretty much got it working upon assembly. I really don't have time to manually wire up complicated designs anymore.
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lb3361
Posts: 188
Joined: 17 Feb 2021, 23:07

Re: Gigatron ASIC and the Gametron Handheld

Post by lb3361 »

bmwtcu wrote: 28 May 2022, 01:56 ... but most importantly I can deal with full 64kx16 ROMs, and in fact can use DIP switches to change ROMs.
Are you using the same IDT 128kx16 memory for both native code and gigatron data? Or is there a second sram on your board?
bmwtcu
Posts: 122
Joined: 01 Nov 2018, 12:02

Re: Gigatron ASIC and the Gametron Handheld

Post by bmwtcu »

The 128Mbit Intel Strataflash between the FPGA and DIP switches stores multiple Gigatron ROM images. The board is laid out such that it can support up to a 256Mbit part that would give you 256 DIP switch selectable 64kx16 ROM images. The IDT SRAM is actually 256kx16 with high/low byte enables. I don't have enough pins on the FPGA in any case to handle more than the 128x8 that would be needed on the SPI/expander, so I just tied the highest address pin and high byte enable to ground/Vcc. The goal here was to use up parts I'd already been hoarding and do something useful with them. The Spartan 2 FPGA itself has probably been obsolete for almost 2 decades at this point. On a side note, the Spartan 6 FPGA dev board I was using previously in the earlier Gametron protos has shot up in price from $25 to more than double that, so I'm in holding pattern until I can settle on something more affordable. Limited BlockRAM for both ROM and SRAM has forced me to stick to a stripped down SDROM and I can't upgrade to ROMvX0. The move to external ROM/SRAM allows me an upgrade path. In parallel, I'm on a mission to answer the question "Can it Gigatron?™" on all the FPGA platforms I have and learn how I can overcome the limitations of each platform. I'm trying to end up with an XIP SPI flash solution in conjunction with at least SDR SDRAM if I can pull it off, so I can use a low cost FPGA board like the Tang Nano 9K. The board has more than sufficient LUTs/FFs, SPI flash and SDRAM, has a SD card slot and a HDMI output, which makes for an interesting hardware platform to learn on. https://wiki.sipeed.com/hardware/en/tan ... no-9K.html
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