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IMU project: Now accepting buyers!


#1

http://www.chrisseto.com/wordpress/?page_id=309

Any takers? 8)


#2

Do you have a working prototype?


#3

Give us the elevator pitch on why yours is better (beside price) than what’s already available.


#4

I love the idea of having a very cheap .NET MF device (therefore based on some cheap CPU like Cortex M0). GHI is missing this kind of device in my opinion. FEZ Mini is the smallest but Panda is the cheapest. Combining those two and event lowering the price could encourage people to develop affordable large scale distributed systems. Right now we can use Netduino Mini but I already tried that. Missing GHI awsome libraries and support was too hard for me to handle :wink:


#5

isn’t netduino mini slightly smaller than fez mini? If you don’t count in the headers and the USB cable then they are about the same size?


#6

How is a cortex any better then an NXP? What is value prop?

I see one with cortex.
http://www.dfrobot.com/index.php?route=product/product&product_id=341


#7

cortex is the new processor from ARM. We had ARM7 and ARM9 but now we have cortex-m0 cortex0m3 and cortex-a8…many other cortrexes! These will replace existing arm processors in near future. NXP already have many cortex processors out and many more are to come.

Why no cortex from GHI yet?..processors are still very new and hard to get and we may run into the risk of having problems with this new technology. But in future for sure :slight_smile:


#8

First off, the IMU isn’t running NETMF. That would be too expensive for no good gain in really anything. This isn’t a flight computer or an IO board, all it does is read its 3 sensors, run some compensation algorithms on it’s processor, then spit the values out.

Why is it better than other IMUs?

Well, let’s take the sparkfun 9DoF Razor.

  • This IMU has a much faster 32 bit proc
  • More than just UART for dataout
  • Less expensive ($~$80 vs $124)

As for the prototype question, we don;t have a prototype yet, we are currently looking for someone who can solder very fine pitch components. for the production IMUs, they will be built by a manufacturer.


#9

What values does the IMU output? Yaw/Pitch/Roll, Rate Of Yaw/Pitch/Roll, Heading, distance, etc…?


#10

It will output raws for each axis/sensor as well as compensated roll/pitch/yaw. FW will be open source, so this can be changed easily.


#11

http://www.codefurnace.com/Man_user_mru_r11.pdf

These are sensors I use quite often (they cost $50,000). Chapter 4 may be of interest to you.


#12

[quote]isn’t netduino mini slightly smaller than fez mini? If you don’t count in the headers and the USB cable then they are about the same size?
[/quote]

Gus–Netduino Mini is a bit less than 35% the size of FEZ Mini: 0.72" sq.

Chris Seto–Please sign me up for one of the IMUs.


#13

Oh, how cool Chris, really small. I wish you didn’t need to add some serial cable to be able to program it. Would have been great if it had a USB connector. Why did you design it with no USB connector? I am not a big fan of serial programming is USB is an option.

Probably still good option for someone out there!


#14

Like FEZ King Christopher I said, we cannot do a production run now since the board wasn’t well proven. We need to make a prototype run and we found one in the U.S. that can make a few bare PCBs fairly low cost and low turn out time. Our problem lies with soldering LGA packaging sensors. Need someone who has the tools and experience to do it.

If you have the tools and exp we are looking for, and are willing to help us, we can consider giving one to you for free.


#15

I can help with some soldering but I suggest you try


or
http://www.aapcb.com/


#16

Here it is:


#17

Netduino Mini might be smaller, but it uses BGA package. I’d rather go with FEZ Mini, because QFP package has better reliability against vibrations.


#18

@ chris

I’m really tempted to sign on. If I’d not been way above my hobby budget, I wouldn’t hesitate. Right now, its between this IMU and TI’s Piccolo F28069 USB stick, and the Piccolo USB stick is just half the price :slight_smile:

Good choice of devices. I’m considering using ADXL345 myself. The one that I have right now is only +/-2g, and gets saturated for larger VTOL aircrafts due to vibrations. I myself was thinking of using a compass unit to compensate for accumulative error. One of my friends ran into noise issues with a compass, but that was for a larger aircraft. He had to stick it at least a yard above the aircraft because the rotors (it was a tendum helicopter) were metal re-inforced. If you’re using outrunners, they can generate a lot of noise. I don’t have any practical experience with how this noise might impact a compass unit, but you might want to do your research on this. Gyroscope is also better than the one that I have, though I’m not sure how you’re going to use full range of +/-2000deg/sec on a quadrotor.

Regarding the processor, have you considered TI’s TMS320F28069 microcontroller? Haven’t done a comparative analysis, but with an FPU, seems like a better fit for this application thatn a Cortex M0. It will consume more power, though. I myself am going to evaluate Cortex M0, but on an Actel Smartfusion platform. That’s number #3 on my list of toys right now, so it will be a while. What operating system are you planning to use? When I looked at the options, FreeRTOS seemed like a good choice.

-Ahmad

p.s. My next project was going to be a FEZ based quadrotor, but I’m way behind you in schedule.


#19

@ Gus

I agree, USB sounds better. But besides the need of having a USB-RS232 adapter does it come with any other inconvenience (also besides speed) ?