Lisa/S, SuperbitRF, 1 BIT SQUARED

Hi everyone,

Again it was a while since I posted something here. I just wanted to write a quick update on what I’ve been up to lately.

I am working very hard on Lisa/S and SuperbitRF. The goal of the project is to develop the smallest and lightest possible UAV controller system without compromising functionality.

lisa_s_top

The Lisa/S board is only 20mm x 20mm and weighs about 3g with a lot of integrated sensors.

  • 3 Axis Gyroscope
  • 3 Axis Accelerometer
  • 3 Axis Magnetometer (Compass)
  • Barometer (Altimeter)
  • GPS Receiver

Just like Lisa/M it’s bigger sister. Lisa/S is powered by the STM32F103 ARM 32bit microcontroller. Providing quite a lot of processing power for your UAV needs. On top of it all the board has 4 MOSFET solid state switches. They make it possible to use the board directly on the tiny brushed motor quadcopters, nano helicopters and fixed wing airplanes. I am quite excited how much I managed to put onto that tiny footprint. Usually much bigger boards don’t even include a GPS receiver on the board.

Another feature of Lisa/S that I think is worth mentioning is that it has a CYRF footprint.

CYRF is a module that I developed as part of the system. It contains the CYRF6936 2.5GHz transceiver chip. It is connected to the MCU on Lisa/S through SPI. The particular transceiver is the one at the heart of all the Spektrum transmitter and receiver systems and many others like Walkera Devo. It is very exciting because we have direct access to that chip from the autopilot and can implement compatibility to a lot of 2.4GHz RC gear available out there.

Our current software implements support for some Spektrum RC transmitters and as a bonus we can simultaneously connect to a laptop using the USBRF dongle. This removes the need for having two radios on your vehicle thus saving weight.

All of these items are currently available for pre-order in the 1 BIT SQUARED shop. We are working on finalizing the production process of the first batch of Lisa/S, CYRF and USBRF. We are projecting they will be available in the shop by the end of May. We have put a lot of effort into making these boards, if you are interested you can read more about it in the 1 BIT SQUARED blog.

Last but not least 1 BIT SQUARED is my own company that I founded early last year. I want to develop and produce hardware and software that I am excited about and would like to share with others that are interested in the field of airborne robotics. If you like open hardware and software and want to support me directly the shop is the most direct and easiest way to do so.

Cheers,
Esden

Black Magic

A few months ago I met a great guy Gareth MacMullin in the libopencm3 channel. He was working on a new Open-Source and Open-Hardware JTAG solution called Black Magic Probe(BMP). I got one of those and instantly fell in love with it.

OpenOCD is great in a sense because it supports lots of targets and probes but that is its disadvantage too. It is very often difficult to set up and tends not to work properly in many cases. The approach of BMP is quite different. Instead of the probe being quite dumb and using OpenOCD to do the JTAG magic the BMP uses a microcontroller (STM32F1) and implements a GDB server inside the controller. This solution cuts out the middleman and talks JTAG as well as the new Serial Wire Debug (SWD) protocol itself. Requiring only a working GDB on the computer.

The BMP supports several Cortex-M3 targets and more devices are being added fairly quickly. The first time I tried it with an STM32 it just worked. No command line parameters just:

arm-none-eabi-gdb some_elf_file
target extended-remote /dev/ACM0
mon swdp_scan
att 1
load
run

It shocked me how fast the loading process was. Because it is not one of the FTDI chips and does not have to bitbang all of the JTAG protocol over USB it can run much much faster. I know there are commercial devices like JLink that have logic inside them but they cost arm and a leg if you don’t want to just get the educational version of it.

One more thing comes to mind when you realize that the BMP supports SWD. You only need three pins to be able to use it GND, SWDIO and SWCLK. That decreases the required real estate on the PCB significantly. I am not sure what the status of OpenOCD support for SWD is now but it is work in progress as far as I understand. On BMP it just works.

Since I started using the BMP there were several interesting developments that Gareth added. The BMP is not only offering one serial port for the GDB extended remote interface but also a second one providing a TTL level UART interface. The BMP also supports tracing by now using the TRACESWO pin. This provides a reasonably high speed tracing. Gareth also wrote a plotter for this feature that plots the contents of traced variables in your code.

Early versions of BMP were 2.5cm X 5cm the current version called Black Magic Probe Mini (BMPM) is smaller, the same size as the FLOSS-JTAG I made a while ago, it is mere 1.5cm X 3cm, packing in all the power of the BMP what makes it great for doing embedded stuff on the go, for example in the subway.

So to wrap things up, it is a high grade, Open-Source and Open-Hardware device. For $60 this thing is a steal!

Shameless plug: On 1 BIT SQUARED store you can order the Black Magic Probe.

There are also some other distributors listed on the BMP page too. So check it out! I bet you will love it. :)

Quadshot – an aerobatic blend of RC quadrocopters and airplanes


Hi everyone,

As you probably notice I am very busy lately. Together with some friends we were working on the Quadshot an aerobatic blend between a quadrocopter and an airplane.

It takes off and lands vertically like a quadrocopter as well as it can fly forward like an airplane using its wing to add additional lift extending flight time.

We submitted the project to Kickstarter and we are very happy to see that we got such a great response. The Kickstarter funding runs for another three days and if you pledge you can get a Quadshot at a discounted price as a reward.

At it’s heart Quadshot is using the avionics and software framework of Paparazzi. We developed the additional necessary controls for Quadshot and released them. So Quadshot has Open-Hardware electronics and Open-Source firmware making it a great platform for research and hacking.

Having an autopilot makes it also very easy to fly for a beginner RC pilot.

I hope to find some more time in the future to get into more details about Quadshot. But till then check out the following links:

Cheers Esden

Open-BLDC and the CLogic story

Castle ICE HV to Open-BLDC Mod Tutorial Step 10Hi,

It was again a while since my last post, but as always I was quite busy. :)

The last news about Open-BLDC was about its V0.3 iteration. A lot has changed and happened since then. I was realizing that I am getting more and more inquires where people were asking about obldc being able to control very different sizes of motors, ranging from 12V and 10A up to 48V and 200A.

This requirement does not really ask for different logic and controls but it definitely asks for many different power stages. Open-BLDC was designed to be modular from the beginning but still to accomodate that kind of a power range it would be necessary to design and create quite a big lineup of hardware.

Around that time I had the opportunity to take a look inside a dead motor controller from Castle Creations just to realize that these guys seem to know what they are doing and that they went with a modular design too. To make a long story short I decided that it will be better to buy one of their of the shelf motor controllers and retrofit them with my logic. That is how CLogic was born.

As it seems other manufacturers are selling ESCs that have the same interface between the logic and the power stage too. Tekin for example. But my guess is that they are just OEM of castle themselves. But who knows. :)

Turingy also came out with an ESC that seems to have the same interface, the Turingy dlux. I ordered a few of them to take a look for myself and see if CLogic will fit in there. That would be a great source of cheep power stages. :)

CLogic has most of the functionality the Open-BLDC v0.3 had. Because of the size constrains I had to get rid of the dedicated i2c and PPM connectors, but I added isolation on the CAN interface that should provide additional safety when used on a 50V and bigger systems. The i2c and PPM interfaces are still available either over the new AUX connector or through the UART interface connector.

The new AUX connector gives the possibility of easily connecting encoders or hal sensors for sensored operation. So the interfaces stay very flexible with added flexibility due to the big variety of power stages you can use, while being very very compact.

Sure some people complained “The power stages are not Open-Source!!!”, yes that is true. Also these systems start at a higher power and weight class than some of you would want to operate them. That is why there is CPico Power. It is a very small, low power and a hopefully cheep power stage that we are putting together for those who want it all fully open! So no worries. :)

I think that wraps up the news about the new direction Open-BLDC is going. I hope you like it. I am looking forward to your comments.

Cheers Esden

FLOSS-JTAG V1.0 Released and Available

Hey everyone,

As you might know some time ago I have developed a small JTAG adapter based on the FT2232H chip. I gave it the name FLOSS-JTAG as the idea was that it should be absolutely OpenSource and OpenHardware.

You can find the project at GitHub and some more info at it’s random projects wiki page.

FLOSS-JTAG not only has the high speed 24MHz FT2232H chip (there are some designs based on my idea that are using a low speed version of the same chip). It provides the new standard 0.05″ pitch 10 pin Cortex JTAG header as well as a TTL level serial interface on it’s second interface.

I am glad to announce that I have reached the V1.0 with it. All necessary files to make your own are in the GitHub repository. But if you don’t want to go through the pains of ordering PCB, sourcing parts, assembling QFN SMD packages you can also purchase it in the Joby Robotics online shop.

At Joby Robotics you get a cable assembly to connect the FLOSS-JTAG to a target. This allows you to debug and connect to targets that are difficult to reach otherwise. You also will get a cortex connector to old standard 20pin 0.1″ pitch connector adapter.

The adapter is small and will make it also easier to debug targets that are difficult to reach.

You can get precrimped Molex Picoblade wires in 10 different colors at Joby Robotics too. This way you can easily build a UART cable that connects FLOSS-JTAG to a device.

I am very happy that FLOSS-JTAG is finally easily accessible to anyone who needs it.

FLOSS-JTAG works perfectly together with Openocd and Summon-ARM-Toolchain.

Cheers Esden

Open-BLDC V0.3 Hardware Based Closed Loop Control

Hi,

Good news everyone!

After again a way too long time some new news! I finally implemented hardware based commutation detection and the associated closed loop controller.

That was quite a run because of a cascade of timing and timer problems. And a very nasty compiler bug. But now it works and very well on top of that. Woohoo o/ But see for yourself in the video.

The video also shows the new implementation of the startup routine. It uses now a separate software timer. It was made possible by using SysTick as timer base and implementing the timer in software. This way it is easy to add new timers that don’t need to be very time precise, as it is the case in startup, or ignite as I like to call it. :) The old implementation was using timer overflows of the commutation timer that led to nasty speed jumps while starting up and made the startup unreliable.

Next step, put Open-BLDC on a plane! :)

As always you are welcome to drop by in #open-bldc channel on freenode if you have questions or just want to hang around to follow the cutting edge development. :)

Open-BLDC Documentation

Today was a big documentation day for Open-BLDC.

As Tobi is learning about Open-BLDC to be able to help me with development I really felt the lack of documentation. So together with him we wrote down how the ignition system currently works. Also I added a getting started page describing how to build the firmware.

Last but not least (that took me most of yesterday) I finally managed to add doxygen generation to the firmware code. It is even being automatically generated out of the git repository and making it available on http://doc.open-bldc.org.

There is still a lot that can be told about the system, but I think we are on the right path. The documentation should grow now significantly when I am not the only person working on the code. :)

Open-BLDC v0.3

Open-BLDC V0.3 Full Front
Hey everyone!

Just a short update so that you don’t think that I have disappeared completely. :)

Lately I am really busy so that is why my updates here are very rare. I have moved to California few months ago to work full time on Open-BLDC and Paparazzi. Although Open-BLDC got quite a bunch of attention there is still a lot to do, and this project is still not in a state where it is possible to put the controller on a vehicle and fly with it. :(

There is some good and bad news. I got the sampling based commutation detection running pretty good. There is an issue with it. Because you can sample the BEMF only once a PWM cycle the resolution prevents turning the motor very fast without adding some kind of an estimator or at least a PLL. So currently only 4000RPM with a 7pole pare motor are possible. :(

That is why I started working on Open-BLDC v0.3 hardware. It is assembled now and you can look at some pictures here. It has a comparator integrated into the power driver board to make commutation detection really easy and have something usable _NOW_. I also found out that using many small mosfet’s is much more efficient then using single big ones. The gate capacitance is lower, the heat dissipation is easier, the on resistance is tiny. The only question is if they will distribute the power evenly between the switches. That is still something that has to be tested. But the power stage board looks really pretty with all those tiny fets on it. There are many more other smaller and bigger improvements that would be too much for such a small post.

I am currently bringing up one subsystem after another. I had to change some of the connections to the STM32 which means that I have to change the low level drivers and it is always a pain to do.

Anyways, there is progress and Open-BLDC is not dead! I am working on it. And I am sorry for not keeping you guys more up to date. As always I will try to be better about that. ;)

Floss-JTAG V0.1 Assembly and V0.2 boards.

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.

Open-BLDC V0.1 Fully Assembled

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.