Using STM32F4 Discovery On a Breadboard

STM32F4 Discover with a Breadboard

You might remember how excited I was getting about the new STM32F4 Discovery board I got a month or so ago. For the price, F4 Discovery is a gem, especially for autonomous robotics applications or demanding control systems alike. The Cortex-M4 STM32 uController has gobs of processing power due to the on-chip DSP (Digital Signal Processor) and hardware floating point unit, ample RAM and a lot of useful peripherals. That in itself is pretty impressive, but ST Micro didn't stop there and made the board even more amazing by adding a ST-Link J-Tag programmer/debugger, 3 axis accelerometer, sound sensor and audio DAC with integrated speaker driver. The only major annoyance with the board is the use of two row headers, so the it can't be used with a standard breadboard out of the box.

There are three ways we can go about fixing this problem:

• Desoldering the male headers and installing female headers (on the top side), similar to the way Arduino Mega is set up. This is the least expensive approach if you have at least basic PCB rework equipment. I was able to get decent results with a simple vacuum desoldering pump, but the process was very tedious, and I managed to lift two or three rings.
• Making a breakout cable from an old internal 50 pin SCSI I/II cable. My local computer store still sells such cables for $3.99. Simply cut a length of cable with a connector at the end, strip and tin the ends and you're good to go.
• Creating an adapter board that fans out two row header into a single row one. This can be done on a large breadboard or using a custom-made PCB. The former will set you back roughly $10 and 2-3 hours of time; the later is a bit more expensive.

STM32F4 Discovery with the adapter board

I've tried all three methods, and settled on the last option, using a custom adapter board. Normally I try to get by without custom boards. My quota of freebies at work is very low and paying full price puts a decent dent in my hobby budget. By breaking the adapter board into two pieces reduced the size significantly. Sunstone has a service called ValueProto geared towards hobbyists. As long as the board fits the ValueProto speciffications*, the prices are much more affordable (especially givent that the boards are made in the USA). I figured that $15 per board ($30 for a set) is a reasonable price for not having to make and solder 100 jumper wires, so I ordered two sets of boards.

*ValueProto alows up to 12"x14" 2-layer boards with green solder mask on both sides, white silk screen on one side and 24 predefined drill sizes

Breadboard Adapter Board Circuit (top layer -red, bottom - blue)

Two adapter boards with the headers

The zip archive linked below, at the end of this post, contains standard Gerber files for the layers, in case someone wants to order those boards from elsewhere. The board can be used two ways: with a male single row header it can be plugged into two breadboards, or with a female header, it can be mounted between the breadboards. I built one set of board in the later configuration, and left the other set unassembled for now. The end result can be seen in the picture at the beginning of the post. The connections don't have any meaning, and are there just for illustration, but you get the idea.

Gerber files: Adapter_Board.zip (the design is shared under Creative Commons license, same as the rest of the blog, so you are free to use it, but please link back :) )