I've decided to ask £10 for a bare PCB, including UK postage.
This might seem quite a lot for a bare board, but I need to try to recoup some of my development costs, which have grown somewhat alarmingly over the last couple of months. I'm also factoring in some time for helping people getting their boards up and running, and answering general FPGA design questions. I hope people feel I'm not being completely unreasonable.
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I've started working on a Beeb 1MHz Bus to FPGA Adapter board.
The goals for this project are as follows:
- create a general purpose platform for a variety of Beeb 1MHz Bus FPGA projects
- get more people playing with FPGAs
- use through-hole technology where possible, so anyone with basic soldering skills can build one
- use a standard/cheap FPGA module for the Xilinx XC6SLX9 chip (to avoid fine pitch soldering)
- try to keep the costs as low as possible
- a standard 1MHz bus connector with terminators (which could be socketed)
- links to enable IRQ and NMI (driven by transistors)
- three 74LVC245A level shifters
- female headers for the eepizza LX9 Core board (which also supplies 3.3V to the board)
- a fast 512Kx8 SRAM (36-pin SOJ, such as the IDT 71V424S12). This is the only SMT component, and it's 1.27mm pitch so easy to solder.
- an MCP4822 SPI DAC (12-bit stereo) feeding two phono outputs
- two general purpose PMOD connectors
- two push switches
- one power LED
- one user LED
https://www.ebay.com/itm/Xilinx-XC6SLX9 ... 1640406811
(ignore the fact the board on ebay looks slightly different)
The PMOD connectors allow all sorts of interesting hardware to be added. See Digilent's pmod catalog. I already have one of these: so one idea was to design a high res VGA display adaptor.
It's also possible to boot software from the 1MHz bus, which might be fun to play with.
Current status is that I've just sent the board design off to JLCPCB so I should have prototypes back in ~2 weeks.
I've got the combined Music 5000/3000 design already to go as an initial test:
https://github.com/hoglet67/Music5000/b ... x9core.vhd
I'll update this thread as things progress.