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Introduction
I designed a small (70mm X 65mm) FPGA board around a Xilinx Spartan 3 FPGA. I decided to make my own for the design experience and it would be cheaper overall than purchasing 4 pre-made boards (excluding time spent of course!). The board contains everything needed to program and run the FPGA + it includes extra memory (SDRAM + EEPROM) and plenty of I/O. Due to the flexibility of the FPGA the boards can be used for many projects.
Features
The board was designed for the following components:
- -Spartan 3 XC3S400
- -2Mb PROM
- -16 bit (data size) SDRAM. Up to 256MB (I think) of RAM. Will be populated it 32MB chip. SRAM can also be used with a few mods.
- 2 X 64KB EEPROM
- -8 LED’s
- -4 DIP switch
- -1 push switch
- -28 GP I/O
- -Standard oscillator
Design
The schematic entry and board design was done using Eagle. Eagle seems to be quite popular, but takes a bit of time to get used to. PCB-POOL also accepts the .brd files made by Eagle which made life easier.
The boards were manufactured by PCB-POOL. The service they provided was excellent and the boards are very high quality, it cost about £65 for the 4 boards.
Status
The board design works. I have made up 3 of the 4 boards which are being used in other projects. As you can see in the last picture, I used a linear voltage regulator instead of a DC/DC converter, due to the low current needed of these supplies, this wont make much difference to power efficiency.
I have also used SRAM instead of SDRAM on 2 of the boards. The pinout between the two is similar but I had to make a few modifcation which can be seen as the yellow wires in the pics