Monthly Archives: September 2015

Lattice FPGA programming adapter from the junk box

Working with Lattice FPGAs recently, I had a need to program one but couldn’t find my ‘proper’ (Chinese clone, bought from eBay) programming adapter. When I started the Diamond Programmer software, though, it claimed it could see a USB programming adapter. It turned out that I’d left an FTDI ‘FT2232H Mini Module‘ attached to the PC. I use the module for all sorts of little debugging exercises: most often as a dual serial port for serial port debugging, but it also works for programming Parallax Propeller microcontrollers.


As luck would have it, the Diamond software recognises the unadulterated FT2232H as a legitimate USB programmer, and pressing the ‘Detect Cable’ button finds it. Note that if you plug in a new USB device, the Diamond Programmer software needs restarting before it can see it.

The FT2232H has two ports, A and B, and these appear as ports FTUSB-0 and FTUSB-1 in the Diamond software. All that remained was to figure out the wiring. Fortunately, there are a lot of clues in the schematics of various Lattice evaluation boards, particularly the MachXO2 Pico Board and the iCE40 Ultra Breakout Board.


Here’s the wiring, both for SPI and JTAG, referred to the pins on the Mini Module. I chose to use port B since it was more convenient for my prototype board. Translating the wiring to port A is left as an exercise for the reader.

SPI    JTAG  FT2232H  Mini Module
SO     TDI   DBUS1    CN3-25
SI     TDO   DBUS2    CN3-24
SCK    TCK   DBUS0    CN3-26
SS_B   ISPEN DBUS4    CN3-21
GND    GND   GND      CN3-2,4

It works well, and does exactly what it should.