Espritmodel.com Telemetry Radio
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Old Sep 29, 2011, 12:01 PM
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Originally Posted by Musgravehill View Post
timecop good work!

What about IMU algorithm? DCM, Kalman? Quarternions/Euler angles?
Do it have horizon drift when copter makes turn (centrifugal force appears and effects on accelerometers)?
I cant see any advantages and features for this price..
How good are your ARM asm skills? Then maybe you can find out.
I need to get myself a USB->CAN dongle (since I'm too lazy to tap the signal after CAN xceiver... though I should probably just do that) and see what format the IMU outputs data as.

Some preliminary testing I've found IMU spits out about 80? bytes of data at 1kHz, then 3 32-bit signed ints (these could be gyro values?) but I need to get this data in realtime and plot it to see the relation as its hard to compare by static analysis.

For some strange reason IMU lamely-encrypts the data, by XOR'ing its output with a random value decided at power up, so it's not exactly hard to figure out but I just wonder why they bothered.

IMU messages on the CAN bus take the most bandwidth, and are transmitted on channel 090 (lowest priority). There is other stuff on other channels (LED, GPS/compass), but I've not looked at them in detail yet. Only IMU appears to be scrambling data.

I find it kind of interesting that magneto is not inside the IMU cube - so there is a possibility the IMU isn't really doing any calculations and just outputs raw data and main controller is doing all the math. But then its weird that they would use a fairly large/expensive FPGA in the IMU .. Who knows. Maybe time will tell.
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Old Sep 29, 2011, 12:32 PM
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TC, is any of the cabling shielded or is it just standard multicore type stuff?
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Old Sep 29, 2011, 12:57 PM
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Originally Posted by timecop View Post
How good are your ARM asm skills? Then maybe you can find out.
Sorry, but Im noob in ARM. Arduino\AVR only. I trying to mod my megapirate copter..

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Originally Posted by timecop View Post
Some preliminary testing I've found IMU spits out about 80? bytes of data at 1kHz, then 3 32-bit signed ints (these could be gyro values?)
May be it RAW data from IMU because its rate is 1kHz. Its quite high speed.

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but I need to get this data in realtime and plot it to see the relation as its hard to compare by static analysis.
I advise you to put system in critical conditions like very fast oscillation or slow drift, or with centrifugal force. You`ll see accelerometers work, gyros response. In home you`ll see IMU work without GPS correction.

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I find it kind of interesting that magneto is not inside the IMU cube - so there is a possibility the IMU isn't really doing any calculations and just outputs raw data and main controller is doing all the math.
You are totally right! Its like sensor board for ArduCopter, which send raw to main processor. It realize DCM algorithm with Euler angles with given data.
Delicate analog sensors like AXRS620 put in separate box. I think, that the main board collects raw data from IMU, GPS and magnetometer. Thats why it can correct linear drift by GPS, and yaw gyro drift - by magnetometer. Or GPS\mag data cross-sending through main board to IMU and processing there. Result returns to main board.
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Old Oct 01, 2011, 04:09 AM
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MrC. cables- shielded or not? I cant tell from piccies

thanks
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Old Oct 01, 2011, 07:46 AM
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TC,
I would guess that they have done proper factory IMU sensor calibration including temperature range calculations and this is where it is stored/used for accurate sensor output for the flight controller.
Cheers,
Jim
Quadrocopter and Tricopter Mega Link Index

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...

I find it kind of interesting that magneto is not inside the IMU cube - so there is a possibility the IMU isn't really doing any calculations and just outputs raw data and main controller is doing all the math. But then its weird that they would use a fairly large/expensive FPGA in the IMU .. Who knows. Maybe time will tell.
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Old Oct 02, 2011, 01:56 AM
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Hi Guys,
ive been trawling the rc forums to get a much information as poss on this FC as I have a Copter control board, fy91Q and a simple KK and Im trying to build a super stable hex for steady hover and this seems tobe the new controller on the block and this would be the most expensive controller ive bought by far and I cant really afford to spend a 1000.00 gbp only to find its not all its cracked up to be.
So would you guys say this is the board to use at this price or should I look at another that could be around this price range??
Your all doing an excellent job...keep it up!!!
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Old Oct 02, 2011, 03:08 AM
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If your budget is 100gbp, you should probably look elsewhere.
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Old Oct 04, 2011, 01:06 AM
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The dji led is super bright. These would come in handy for led light projects. Any idea where I can source them. Part number any info?
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Old Oct 04, 2011, 01:21 AM
by Alary Design
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While not really spectacular, that's 5ms, and is probably more than enough for a stable platform. I was told anything below 25ms is acceptable for multirotor stability as things like motor response and etc are the biggest factor here.
That's an interesting comment from you because on Sept. 8th in another thread you said:

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Mikrokopter main loop runs at < 500Hz, 480-ish or so.
If this flies properly, I'll be surprised. So for the last motor in the order, throttle change command could come as much as 1.8ms later.
As far as I know 25ms is far greater than 1.8ms. What gives?
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Old Oct 04, 2011, 03:08 AM
not surprised.........
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Troll Alert !!!!!!!!!!!!!!
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Old Oct 04, 2011, 05:35 AM
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Yeah DJ is pissed because TC said his overpriced power distro board is uncool
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Old Oct 04, 2011, 09:25 AM
by Alary Design
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numbers are numbers guys. numbers are unbiased. my questions stands.
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Old Oct 04, 2011, 01:34 PM
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That's an interesting comment from you because on Sept. 8th in another thread you said:



As far as I know 25ms is far greater than 1.8ms. What gives?
People I won't mention keep saying how "amazing BL-ESC" is amazing because it will respond in < 150ms normal ESC responds in. So apparently adding 2ms on input is "bad idea". And yea, troll alert, I should just delete all the stuff since its MY thread ^_-
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Old Oct 06, 2011, 03:40 PM
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Hi timecop
With regards to my post about buying a quality flight controller and my price range.. I think you might have misread my post as I my price range is not 100.00 gbp but 1000.00 gbp...so how does the DJI stand up against other FC's in the range as I can pick one up tomorrow if there worth it?
Regards
Paul
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Old Oct 07, 2011, 09:25 AM
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Eyeball Get a mikrokopter set up. It has more features and far better support now. You have the option of speaking to the holger the creator personally he replies to emails. Not like dji who seems to be cocky and thinks we the costumers must beg for new features, answers and email reply.
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