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Old Dec 22, 2010, 02:52 PM
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Originally Posted by Niall View Post
Good idea on the single board. One of the things that has really put me off is the Wii variability. There are SO many different clones and connecting them up is not as straight forward as it could be.

I have also been thinking about modular plug and play sensor boards that can be built up from DIY for peanuts or sold pre-assembled for the KK line. Perhaps we could combine efforts and make some sensor boards that will work for both projects?

If anyone is interested I can help fund development work on this.

Cheers,

Niall
Thx for chiming in, Niall.
We should get some of the masterminds gathered anyway, I think.

There are so many great projects dealing with ATmel/Arduinos and different sensors, we could start with modular setups right away if someone is willing to make some efforts getting this all sorted out.

If we keep it split in too many different groups it feels like a waste of talents and energy to me. Let's go for something, ALL projects could benefit from!


What I have in mind is something real cheap and easy, flyable, plug & play board to start with on the grounds of a scalable & modular code base, covering the basic needs for a stable fun copter.

- Alex' MultiCopter code on an arduino mini pro with gyros (and maybe accels) for a low cost version for beginners - alternatively could also be split into brain and sensor board

up to...

- Aeroquad/ArduCopter/whatsoever Arducode on an Arduino Mega / ArduPilot Mega with all damn features a Multirotorist could dream of: autonomy, position hold, waypoint navigation and such.

If we start with something like Norf did on a single board we'd be one big step further...
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Old Dec 22, 2010, 03:46 PM
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K.I.S.S. is the key or otherwise are available lots of options with lots of $$ : Arducopter, Paparazi, MK etc.

Alex is the only software developer and you all guys are many. Let Alex write the code as he knows, for current CHEAP hardware and you develop hardware for his soft, not vice-versa.

Modularity is good: Try to make a CHEAP 6IMU shield with I2C comunication bus usable for Duemilanove/arduMega.


Please reconsider the use of arduino pro mini with his wired motherboard as a shield:
Building a standard size 6IMU shield for duemilanove/ardumega who could accomodate Ardumega or even other software applications is the way to go.
Using the 6IMU shield in other aplications could make the shield even more affordable.
How difficult would be to hack the IDG650 giros from WMP+ and put your own I2C controller with ADC on a shield? Same with NK accelerometers.
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Old Dec 22, 2010, 04:11 PM
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I second the usage of the AT90USB uC. This frees up the serial connection for onboard GPS. I would also like to see the SS/MOSI/MISO pins broken out for an OSD option (the MAX7456 chip, for example). If the consensus is to keep the uC on a separate board, the Teensy++2.0 is a perfect candidate to build around. Paul at pjrc.com has them back in stock now, after the inrush of orders to jailbreak the PS3. All of these options do not add cost to the bare pcb, and the user can add chips depending on desired options.

my .02,
Billy
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Old Dec 22, 2010, 04:22 PM
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I have been thinking about making a board with Atmega328, IDG655 and IXZ650 (from a WM+) and a ADXL335 (from a NK). This requires a rewrite of the code the use the ADC, but it should be easy.
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Old Dec 23, 2010, 03:19 AM
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Thanks for all the suggestions and replys......keep em´ coming!

I will look into the possibilty of adding analog sensors to the board. But I really think i2c is a huge advantage in terms of uC processor time. And as such I think we shoudl try to keep sensors digital.

I will look into the ITG3200 from Invensense, as this is native i2c....but I havent been able to locate it as single chip (anyones got a supplier). And ADXL345 instead of 335 (Or bma020). I am still convinced we shoudl be able to bring sensor price down significantly over breakout boards!

Alternatively we could consider the use of a second small uC for ADC. Something like a tiny or similar should work well. If we could increase ADC resolution it probably woudl be a good thing.

As for analog sensors, I am still convinced that ADXR610 is the one to go for.....but its hell on earth to solder those - and it probably cant be done without reflow

I am also waiting for Alex´ opinion on this!

Merry christmas to all of you.....
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Old Dec 23, 2010, 04:15 AM
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Invensense Gyros can be ordered directly through their Yahoo shop (10$):
http://invensense.com/mems/gyro/itg3200.html

The Bosch BMA020 can be ordered from Digikey (5$):
http://parts.digikey.com/1/parts/163...-f-bma020.html
Alternatively the Bosch BMA180, since one user got it working (7,30$):
http://parts.digikey.com/1/parts/201...x3-bma180.html

The BMP085 pressure sensor can be ordered from Future Electronics (5$):
http://de.futureelectronics.com/de/t...273300144.aspx

Honeywell 3axis compass from Digikey (4$):
http://search.digikey.com/scripts/Dk...=342-1082-1-ND

MTEK 3329 GPS chip (25$):
http://shop.trenz-electronic.de/cata...56&language=en

ATMega 328 can be purchased for ~ 5$:
http://search.digikey.com/scripts/Dk...ords=atmega328

ATMEGA 1280 can be purchsed for ~ 17$;
http://search.digikey.com/scripts/Dk...9&k=atmega1280
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Old Dec 23, 2010, 05:33 AM
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http://www.seeedstudio.com/depot/see...ml?cPath=79_80

Has anyone thought of using something like this?

Cheers,

Niall
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Old Dec 23, 2010, 06:39 AM
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Quote:
Originally Posted by 420RcPilot View Post
Thanks for all the suggestions and replys......keep em´ coming!

I will look into the possibilty of adding analog sensors to the board. But I really think i2c is a huge advantage in terms of uC processor time. And as such I think we shoudl try to keep sensors digital.

I will look into the ITG3200 from Invensense, as this is native i2c....but I havent been able to locate it as single chip (anyones got a supplier). And ADXL345 instead of 335 (Or bma020). I am still convinced we shoudl be able to bring sensor price down significantly over breakout boards!

Alternatively we could consider the use of a second small uC for ADC. Something like a tiny or similar should work well. If we could increase ADC resolution it probably woudl be a good thing.

As for analog sensors, I am still convinced that ADXR610 is the one to go for.....but its hell on earth to solder those - and it probably cant be done without reflow

I am also waiting for Alex´ opinion on this!

Merry christmas to all of you.....
Hej Jussi,

This might be of interest if you want to play with ADC's.

http://store.gravitech.us/i2c128anco.html
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Old Dec 23, 2010, 06:46 AM
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Quote:
Originally Posted by 420RcPilot View Post
Thanks for all the suggestions and replys......keep em´ coming!

I will look into the possibilty of adding analog sensors to the board. But I really think i2c is a huge advantage in terms of uC processor time. And as such I think we shoudl try to keep sensors digital.
In the case of the Wii Motion Plus, it is not digital, the Gyros are Analog and it has a ADC on-board. The ADC that are built into the Arduino are much better and faster. On my VTOL, the Cycle time is 3700 using the WM+ and on development controller using the 3 axises Flymentor gyro, the Cycle time is about 2000.
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Old Dec 23, 2010, 07:08 AM
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I think two different approaches are viable here, I changed my mind and propose solution 1 first.:

1- Do an all-in-one board (with gyro and BMAXXX) that is 100% code compatible. That would be an alternative for a KK, but with the benifit of accelerometer stabilization.

2- Go all out with a more powerful uC such as the Teensy but make it modular. One board for the uC (just use the Teensy?) and one board for the sensors.

My 2˘.
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Old Dec 23, 2010, 08:47 AM
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Originally Posted by 420RcPilot View Post
As for analog sensors, I am still convinced that ADXR610 is the one to go for.....but its hell on earth to solder those - and it probably cant be done without reflow
I have been told by several that the Analog ADXR gyros are very sensitive to vibrations, so I do not think this is the was to go.

The reason for choosing the analog sensor are because they are still cheaper than those with integrated ADC. And the Arduino would easily handle the conversion, without having impact on the cycletime.
The way to do it is to start the conversions some time before you need the results. When one conversion is done you get an interrupt, read the data and start the next conversion. This way you can do all the loop calculations while the ADC running.
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Old Dec 23, 2010, 08:47 AM
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Hi,

Some thoughts about the choice I made at the beginning:

- cost: I think one of the main interest of MultiWii is the ability to construct a basic flight control board for only $30 or $40. Even if this board can't compete with the more elaborated ones, I 'm convinced there is a demand for very simple boards because multi are just as fun as piloting as other planes or helis. There is no reasons to see only videos where multi are only static, and I'm happy to see people like warthox opening a new way I think KK has the same approach when he designed its board.
-simplicity: I know most RC hobbyist are not fluent about electronic things. So the basic board was thought to be easy to setup with no external components shield/resistor/capacitor, only 2 very well deployed components: Arduino and WMP.

WMP:

I'm sure it's still the best deal regarding the cost/performance.
Genuine WMP are 100% predictable even if they cost $10 more.
There is a way to save a little money buying a copy, but results are not guaranteed. There are too many copies in circulation.

I2C or ADC:

Atmel 328p has 8x10 bits ADC inputs (only 6 are available on the pro mini, but it's a board limitation).
Projects like KK or Shrediquette use it with great success for ADC gyro (HK401 or ADXR610) or ADC acc.
I like I2C because it's convenient to stack multiple sensors, but we have to deal with other issues.
- I2C sensor retrieving time is higher than ADC retrieving time (for coders analogRead() is faster than getting I2C data at 100kHz clock speed)
- I2C must be properly adjusted regarding the compatibility Voltage on the wire
But with I2C there is no sensor limit. Gyro+Acc need 6 ADC inputs, and nothing more could be added after on the small pro mini with the only ADC approach.
Even some GPS can be accessed via I2C now.
Sensors with integrated ADC and I2C communication seems to become a standard solution.

About a new sensor board:

I'm quite agree with Niall: a common sensor board *at the right price* for multiple projects would be great ! It's not difficult at all to adapt MultiWii code to speak with one or other sensors, I2C or ADC.
I integrated today only the WMP gyros because it's to my mind the best option today, but I would be happy to integrate other sensors if they are as cost effective.
BMA020 accelerometer is a good example of Wii NK replacement option.
I know nothing about the PCB industry, but even for more elaborated boards with acc/baro/magneto/gps, I think there is a way to design a nice and cheap PCB if we consider the cost of individual components. It would be a nice challenge.

About a new processor board with or without basic sensors:

When I see what you are able to do in the design of shields, I think it's possible to go for a more powerful processor. If it's still Arduino compatible, the effort to port MultiWii on it would be minimal. No problem to adapt the soft to the hard
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Old Dec 23, 2010, 08:50 AM
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And how about using one Atmega 644 running at 20Mhz?
It would still be available in DIP package, and would be faster than the 328p running at 16Mhz, I have already ordered some Atmegas 644 for my first custom quadcopter and I will use it at 20Mhz, I dont think that using the internal ADC versus an 14 bits ADC is better and you can only sample at aprox 16Khz.

If you buy bulk quantities the prices will drop a lot.
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Old Dec 23, 2010, 08:56 AM
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it s good idea to create a board for multiwwi
i like it
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Old Dec 23, 2010, 09:02 AM
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Alex, from what I have been able to complied at this stage, I COMPLETELY and Fully agree with your approach. As for the I2C stacking, what I visualize is, using an analog Gyro and Accelerator for the main flight control because of the critical nature and everything else can be I2C such as GPS, Barometer etc.
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