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Old Mar 01, 2011, 08:38 PM
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Newer I2C to PWM converter for standard ESC

Since the other thread unfortunately demised, here's a new one.

This is a newer protocol converter for I2C to PWM. It allows the use of standard ESC controler on original Mikrokopter Flight Control as well as any of the MK clones, or any Flight Control which controls motors by I2C.

One of the major drawback of I2C currently, is in case of severe failure on one controller, you may impact all other controllers connected to the I2C bus and lose all motors. Choosing PWM is more reliable, as each controller is connected separately, it may not interfere with others and reduce a lot the risk of losing all motors. It allow also to use well proven standard controller with a wide range of choices.

Features:
- I2C input from Mikrokopter or similar Flight Control supporting same I2C protocol
- NEW I2C input from LotusRC T580 Flight Control
- output PPM signal suitable to standards ESC motor controllers
- support 4 or 6 or 8 or 3 controller
- Configurable PWM frequency from 100 to 500Hz (If your ESC can't do >400Hz, throw it away).
- Configurable pulse start/end points for custom ESC
- Automatic throttle calibration for all ESCs at once
- User-upgradeable firmware

Mis-features:
- Using PWM is inherently slower than I2C. 2-3 I2C speed updates can occur during a 400Hz PWM pulse. Don't expect miracles with precise control. However, it is definitely flyable:

AfroCtrl 1.39c + AfroI2C stability/flight test (1 min 43 sec)


Not all ESC may work with 400Hz update speed, or may not be usable for multi-rotor application. Generally, cheap Chinese ESC (Turnigy Basic, Plush, SS series from HobbyKing, etc) are known to work.
More expensive stuff from Castle Creations, ESCs with programmable throttle curves and other "smart" features should generally be avoided. Also, due to the nature of how PWM ESC works, there's no longer any feedback about current used or ESC temperature, etc, so this information is not returned by this converter.

There are two revisions of the board available. Both are actively developed and share same feature set.

STM revision
Uses STM chip for 8 channels of hardware PWM with no measurable jitter. Precise timing output and serial console for firmware updates without needing special programming cable. Can be re-flashed by MKUSB or similar USB to serial converter. Can be powered by external 5V, 5V from 1st ESC, or from up to 4S LiPo battery.

ATmega168 revision
Uses mega168 for software PWM output with ~100ns jitter (for reference, AR6100 per channel jitter is ~800ns) . Firmware will be opensores eventually. The board is firmware is user-upgradeable using standard AVR-ISP 6-pin connector. 5V power has to be provided separately, from FC or by BEC, etc.

Both versions can be configured for tri/quad/hexa/octo configuration by solder-bridging 3 pads on the back side of the board.

Bind plug (ESC Throttle auto-calibration)
By connecting a standard receiver bind plug (3-pin connector, which shorts out 1st and 3rd pins) to the I2C pins and powering up with all ESCs connected, throttle set mode is entered. Output throttle to all controllers is set to max for approximately 3 seconds, then lowered to min to set throttle range. This should be done once after connecting new ESCs. After ESC beeps to confirm range setting, power everything down, remove bind plug and replace I2C connector.

On power up, converter outputs min-throttle for a few seconds, then blinks number of motors its configured for:
AfroI2C Power-up and motor detection (0 min 15 sec)


If you're still reading and want some, you can get them here: http://www.abusemark.com/store/

Documentation, firmware downloads, etc

Manual for ST version
Manual for ATmega version
Rusty's review of ST board and what to expect when flying it.

To ensure optimal operation, always download latest firmware and update. Boards may or may not be shipped with latest firmware pre-loaded.

STM: latest firmware / firmware update utility

ATmega: latest firmware

Safety

Please make sure to test this converter with propellers REMOVED. I will not be responsible for broken faces as a result of not following this warning.

PWM ESC Programming instructions

Hobbyking BlueSeries (aka Mystery) http://www.rcgroups.com/forums/showp...&postcount=604
Turnigy & clones http://www.rcgroups.com/forums/showp...&postcount=606
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Last edited by timecop; Jul 01, 2011 at 12:13 AM. Reason: updated manual for ST converter
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Old Mar 01, 2011, 08:47 PM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
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Hi,
Price? Shipped from? *Edit Thanks for adding it. ~$30 to the US sounds like a winner That thing is so small you can hide it anywhere too
Cheers,
Jim
Quadrocopter and Tricopter Mega Link Index
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Old Mar 01, 2011, 09:22 PM
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Navarre, FL
Joined Mar 2002
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Wow, the yen doesn't go very far does it

I'm always interested in seeing these converters. I'd like to see this made into the same form factor as the MK boards though. That would allow it to fit in the normal stack, and also avoid all the stacked connectors. You could just have two on each side of the board. Just a thought.

Cheers,
Rusty (waiting for the non-jitter version)
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Old Mar 01, 2011, 09:27 PM
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That's a cool idea and I can see where you're going with that (have like 1/2 ESC connectors on each side to make wiring less messy), but that would be a giant waste of PCB space, since all it would have is a 7x7 chip in the center of it. However, definitely something to consider.
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Old Mar 02, 2011, 02:24 AM
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subscribed great job!
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Old Mar 02, 2011, 02:53 AM
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Quote:
Originally Posted by timecop View Post
3 pads on the back side of the board can be solder bridged for hexa/octo/tri (does any tricopter even use i2c)? configuration.
http://www.mikrokopter.de/ucwiki/Tricopter

Q4 Unique Trikopter (2 min 19 sec)
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Old Mar 02, 2011, 03:16 AM
a little boy's dream come true
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France, Corse, Santo-Pietro-di-Tenda
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he he, here we go!
At least we know this thread won't close abruptly
Rusty's idea is a good one, I find having the bits and pieces all around the MK stack a bit messy.

Keep the good work TC.
Bob
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Old Mar 02, 2011, 06:41 AM
Tri-Quad-Hexa-Octo-copters!!
United States, TX, San Antonio
Joined Feb 2007
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@Sebastian,
Nice find. I did not Know anyone had modified Mikrokopter firmware successfully for a tricopter version
@TC,
FYI:...Here is another nice I2c Tricopter by William Thielicke:

Tricopter - The Movie... (8 min 7 sec)


His blog spot for his open source designs: http://shrediquette.blogspot.com/

Featured on Japanese TV: http://4.bp.blogspot.com/-L76k1fy5uE.../s320/doga.jpg
http://doga.nhk.or.jp/doga/viewvideo...evee375190.flv His hexacopter part is from 01:35 - 04:00.
Quote:
Originally Posted by timecop View Post
...3 pads on the back side of the board can be solder bridged for hexa/octo/tri (does any tricopter even use i2c)? configuration.
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Old Mar 02, 2011, 06:50 AM
a little boy's dream come true
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France, Corse, Santo-Pietro-di-Tenda
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Quote:
Originally Posted by jesolins View Post
@Sebastian,
Nice find. I did not Know anyone had modified MikroKopter firmware successfully for a tricopter version
@TC,
FYI:...Here is another nice I2c Tricopter by William Theilicke:

http://vimeo.com/6766174

His Blog spot for his open source designs: http://shrediquette.blogspot.com/

Featured on Japanese TV: http://4.bp.blogspot.com/-L76k1fy5uE.../s320/doga.jpg
http://doga.nhk.or.jp/doga/viewvideo...evee375190.flv His hexacopter part is from 01:35 - 04:00.
I remember seing this video a while ago, it still feels the same : NICE

Bob
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Old Mar 02, 2011, 10:33 PM
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Timecop -

I'm going to need to start with two of these, and then get more later! To whom do I send funds?

Also - On the 'other' i2c converter, there were reports that loading modified firmware onto the Turnigy Plush ESC's would make them work even better than they do 'off the shelf'.

Do you think that modified firmware would help improve the performance of yours?

Seriously, I want to buy two for now.
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Old Mar 02, 2011, 11:01 PM
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I'm not sure re: firmware.
400Hz is 2.5ms.
500Hz is 2ms, which means if standard pulse width is used there isn't gonna be any space left between the pulses for the ESC to find at max throttle.
Unless there's something that increases ESC's timing while using shorter pulse widths there's probably not much to improve. The only real improvement would be using different MCU with hardware PWM outputs.
Note I've *only* tested this with Turnigy Basic 25A.

A few review units were sent out to people who hopefully know what they're doing, and have more different ESCs etc to try with.
Shoot me an email if you want the two, ill send a pp invoice there.
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Old Mar 03, 2011, 06:26 AM
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Interesting ! Very ! An cheap - I am in japan

Do you confirms it works with the clones 1.35 ?

I look forward to know how good this work with some Plush ESCs
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Old Mar 03, 2011, 06:36 AM
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It works with my clones of 1.3 an 2.x so I would imagine it works with ChinaFC as well. Since that was kind of hard to screw up in the first place (not sure how the other converter managed to do it), I'd assume it works rather than not.
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Old Mar 03, 2011, 07:11 AM
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Nice product .. One of the issues I have with MK is the "requirement" for i2c esc's .. ( I think thats really just because they dont want the hassles that will come from low end pwm esc's )

One issue however ,

Quote:
One of the major drawback of I2C currently, is in case of severe failure on one controller, you may impact all other controllers connected to the I2C bus and lose all motors. Choosing PWM is more reliable, as each controller is connected separately, it may not interfere with others and reduce a lot the risk of losing all motors.

Is this really an advantage ?? Loss of one motor on a quad == crash !! .. Even in theory , the only thing you can do is to kill the motor on the other arm ( go to BI mode ) , and try and float down gently ( with very fast uncontrolled yaw )

flat hex the same thing ..

Coax hex ( y configuration ) can survive a motor loss .. As can octo .. but tri quad and flat hex can not ..
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Old Mar 03, 2011, 07:12 AM
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Oh, I don't really care about that part.
I just copied that from the other thread.
I think with MK firmware, loss of any motor is pretty much crash regardless of things.
A single converter instead of a spread-out bus with many connections and own pullups on each point IS better for I2C because when I scoped I2C lines on my MK-hexa, the rise time was horrible, almost half of what it should be. So it is an advantage in that case, but surely isnt gonna do wonders in a crash.
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