More information on all the projects I'm working on can be found at my website:

As you may or may not remember I hadn't got my crazy experimental airframe flying (Talon: )

Well, I diverted onto a quadcopter frame I have designed and built in order to test the electronics and my code, and here it is working, reasonably well! Though many more improvements are yet to be made!

In the first clip I simply increase the collective throttle, with stabilisation enabled, and then catch it as I have no directional control to prevent drift.

In the second clip I have done some p d loop tuning and have it happily responding to inputs from the transmitter. I'll follow this blog up with some more videos soon!

Excitingly we will be giving a demo at the London Hackspace this coming Tuesday:

In the near future we will be running quadcopter and uav workshops at various locations in the UK and publishing each as a video guide on YouTube.

We intend to publish a comprehensive guide on PID loop tuning for model aircraft - it was very exciting to immediately swap the electronics into two other airframes we have (including Talon) and with only an hour or so of fiddling, have them flying stably too!


As normal, comments and ideas appreciated!

Views: 366

Comment by robert bouwens on August 11, 2011 at 10:41pm


looks nice!

also the sensor boards  - prob. due to the fact a nxp cortex device sits beneath:)

question, does the sensor board fit on a 1769 lpcxpresso board ?

i need raw processing power for my next tests.



Comment by Henry Fletcher on August 12, 2011 at 6:42am

Heya Robert,

Nope, the Seraphim board won't fit on the larger LPCxpresso board, which has a different pinout. The difference between the 1343 (which we use on Forebrain) and the 1769 on the LPCxpresso is the clock speed and peripherals, they are the same family/same architecture, but the 1769 runs at 120MHz and the 1343 runs at 72MHz. In terms of raw processing power the 1769 has a 66% higher instruction rate, but you'd be pleasantly surprised at how much you can fit on even the 1343.



Comment by Yuan Gao on August 12, 2011 at 7:01am

We have an LPCxpresso with LPC1343 for testing purposes, they're nice boards (especially with the debug), but they don't have a USB socket installed (for loading the firmware really easily - the LPC1343 has a built-in USB bootloader, which the LPC1769 doesn't, you can add your own USB port and flash a secondary USB bootloader, but I think you still need to add the 33ohm resistors and the D+ pullup resistor).  No voltage regulator or EEPROM on board either.


I think the Forebrain dev board is looking like it's prefect for UAV use.  Disclaimer: I'm extremely biased in favour of Forebrain.

Comment by robert bouwens on August 12, 2011 at 7:19am

hi henry,

i have both lpcxpresso sticks. i would prefer the 'bigger' device because of the flash memory size.

raw performance of a cortex device is nice - enough to run your sensor fusion algorythm.

would be very interesting to know more about your algorythms behind the sensors.



Comment by Henry Fletcher on August 12, 2011 at 7:31am

Hi again,

There is a bit more information on our website:

I don't know if you have had a chance to look, but I'll tell you roughly what we are doing as there isn't any specific info up yet:

With Forebrain, we find our code fits fine, 32-bit microcontroller code tends to be a fair bit more compact than 8-bit microcontroller code.  Our algorithms are quite simple - grab some PWM readings off the RC receiver, read sensors off I2C, run a DCM, PID, and then output PWM, all this is currently unoptimised running at 50Hz, we can comfortably increase the DCM and sensor frequency beyond 400Hz, and maybe five times more than that when optimised (but no point really).  Have plenty of space and spare processor time to deal with GPS and navigation.
May look into EKFs later.

Hope that's of use! If you fancy finding out more, start a thread on our website forums or feel free to email me: henry(at)




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