Because I wanted to have a small JTAG adapter with additional UART port and a different (smaller) connector then what is available out there, I have decided to make a JTAG adapter. I chose the FT2232 USB adapter chip. This guy is pretty nice because it has a special engine inside that is supporting many different protocols. One of them is JTAG. I have released what I made as always on GitHub under the CC-BY-SA 3.0 license. There is no software needed on the adapter side so no software included. All you need is OpenOCD. It now even has a config file dedicated for Floss-JTAG. Calling for example:

#> openocd -f interface/flossjtag.cfg -f board/open-bldc.cfg

will connect to Open-BLDC using the Floss-JTAG adapter.

Building Floss-JTAG I learned a nice lesson. Always check your footprints 10x before you send the gerber files to the manufacturer!!! I had to customize the footprint for the FT2232 chip and made a mistake. The pads were not long enough so the pins had only 0.1mm overlap area. It was a real pain to solder that. I assembled 3 of Floss-JTAG using this design. Sadly only two are working.

Because of that mistake I immediately corrected the board layout and sent it out. I got the boards today. I hope that there is no other mistake hidden somewhere. :) Attached are the images of V0.1 assembly and of the V0.2 boards.

I finished soldering Open-BLDC V0.1 boards and took some pictures while doing so.

After connecting it to the power everything seems to work properly and nothing is burning. That is really good news.

One little thing that is bothering me. The board draws 60mA, what is a value that I expected. The 5V linear regulator gets really warm. I am not sure if that will be a problem or not. But I did not find any other problems or screwups yet, even the big MOSFETs can be soldered using a simple soldering iron. It takes some time though, because the board and the MOSFETs are monstrous heatsinks.

More news coming up as soon as I start playing around with the software.

I assembled the basic STM32 circuitry of Open-BLDC and it works. I also made a video showing the logic board and blinking around. I know it is a bit pointless but I love blinking LED’s! ;) I wrote the software using libopenstm32.

Have fun:

Video on Youtube and here the same video on Vimeo.

While assembling Uwe and I made some photographs that I don’t want to hold off either.

Only a short note. I made a video showing all the different PWM Schemes Open-BLDC supports. Have fun watching:

Cheers Esden

I started to build up the Open-BLDC circuit on a breadboard. Then a problem occurred. The low side works as it should but the high side just did not. After several hours of trying and reading the data sheet of IR2110 I gave up and asked Federico again for help. After some time we found an application note AN-978 from International Rectifier. This explained everything. You need to select very carefully the Boot capacitor. This is the one between VB and VS pins of IR2110. It is providing the charge for the gate of the high side MOSFET when you turn it on.

For testing you can take a big capacitor, so that when you manually switch on the high side you see something happen. I took a 330uF capacitor and it is enough to turn the high side MOSFET on for about 30 seconds. Still you have to be careful because the capacitor only gets charged when the low side MOSFET is turned on. So after turning on the power the capacitor is not charged and you have to turn the low side MOSFET on first, then turn it off again and finally switch the high side on.

In the final design one should probably select the right bootstrap capacitor. The equation for calculating that value is described on page 6 of the International Rectifier application note AN-978.

You can probably get rid of the capacitor and the diode if you connect VCC directly to VB. The problem you get then is that when the current on VS gets higher then 12V you get a problem. But I may be mistaken. Correct me if I am wrong.

Conclusion: read the damn application notes and I still have problems with understanding the electrical engineer talk! :)

I hope this helps someone. You can see my circuit for one half bridge attached to this post. And a picture of my breadboard.

I use the two LEDs to see what happens with the MOSFETs. They are glowing a little when both sides are off. The one connected to 12V is switching off when the high side is on and the one connected to GND switches off when the low side is on. I love LEDs! :)

Cheers Esden

I am currently working on building a breadboard prototype of Open-BLDC. I will write about that in more detail in a separate post. I had a problem there. The Olimex STM32 board has two dual in line connectors that just don’t fit on a breadboard. There are some adapters that you can buy for money, for example from Number Six. But that would cost me too much time and money.

So I decided to build my own adapters with parts that I had ling around and a prototype board that I got from Uwe. (Thanks Uwe I will buy one and give you a replacement as soon as possible!) It was a lot of fun building the adapters. They are really easy to make!

Step 1
Just cut out piece of prototype board with the length you need and four holes wide.

Step 2
Solder a dual in line connector to the copper side of the board. Just don’t push the connector completely into the holes so that you can reach the copper with your soldering iron.

Step 3
Solder two single line pin connectors on the other side of the board, right and left of the dual connector.

Step 4
This is a bit tricky. You can use some wire to connect the pins of the DIL (Dual In Line) with the single line connectors. But I found out it is much easier just to put a bit more solder between the pins and let them connect. You may have to try one or two times. Having some desoldering wick around is a good thing if you happen to solder together wrong pins. ^^

Step 5
Profit! ;)

I appended some images you may consider more or less useful. I should make one more adapter to document the build process. :/ I am sure there will be such an opportunity soon.

Cheers Esden