Another Cheap and Simple FPGA Board

29 Oct 2020

A lot of the recent discussion of FPGAs on E14 recently has been focused on huge great SOC type parts running Linux - this project is at completely the other end of the scale.

I'm looking at using Gowin's FPGAs in a couple of new designs where small size and low cost are important. Although Lattice have some small cheap devices they have limitations

and you can't get more than 48 pins without getting into very fine pitch BGA packages.

Gowin do a GW1N-9xxx part in 88 pin 0.4mm pitch QFN package, with a built in 8Mbyte SD Ram. (The built in SD Ram is a bit like getting another 40 pins as well as the memory.)

These are $5 in modest numbers (about £10 in ones from Mouser).

I designed a break out board for this chip which can (using an adapter) plug into a test board I designed with a different FPGA in mind, it has a reasonable 96ks/s stereo Audio Codec,

4 channel 24 bit ADC, and a switch mode full bridge 12V, 7A power stage designed to be FPGA controlled.

The breakout board for the Gowin FPGA has the least possible stuff on it, 3.3V regulator, 1.2V regulator, oscillator, connectors for every IO pin and a JTAG connector.

You can JTAG the Gowin FPGAs using a blank FTDI 2232H chip and Gowin's software.

My in house surface mount assembly is just about up to placing and soldering the 0.4mm pitch QFN (the two I've done look OK and at least one of them works !).

This is the FPGA board style I mean to use on the Earth Resistance Meter board.

So far the FPGA is only running a very simple test code but it doesn't use a lot of power (25mA at 5V, the 5V to 3.3V regulator is linear so it's wasting about 33% of the power).