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Old Jan 27, 2008, 11:39 AM
veni,vidi, roto volubilis
Happy|Harry's Avatar
Aberdeen, Scotland
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awesome work alan!, very cool though way over my head lol

phil
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Old Feb 07, 2008, 04:54 PM
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Snohomish, WA
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Alan,

Sounds like you have made a pretty reliable link (hopping, reconnection, etc.) That's better than what XPS has been doing recently (see http://www.rcgroups.com/forums/showthread.php?t=814276). Are you still using just the basic 2 channel system as described in the first post or have you set it up with any more channels?

-Jeff
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Old Feb 07, 2008, 06:42 PM
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Phil,
Thanks, it's nice to find a UK product

Jeff,
I keep meaning to do some tests to see if I can generate more channels of servo pwm outputs without further hardware however my main projects at the moment are toy boats and cars for my son and small dlg gliders for me, all of which only need two outputs so it is not a high priority. If it turns out that software pwm has too much jitter it shouldn't require much extra hardware to generate extra channels.
My dlg Alula has active angle of attack feedback and I am in the process of interfacing a playstation controller to the transmitter to enable me to send a whole host of extra channels to it to allow me to control control loop settings on the fly. A buddy box style of interface would also be fairly trivial as the modules have hardware capture timers.
I am slowly drawing up some pcbs for both tx and rx and will post them along with the software fairly soon(I hope).
Alan
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Old Feb 08, 2008, 02:33 PM
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East Hartford, CT
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wow!!! Awesome job Alan!!

I'll be buying some of these modules this weekend and see if I can duplicate your tests with the higher power TX and RX.

This sounds like the perfect solution to building a low cost 2.4Ghz TX.

Do you think the bandwidth is good enough to transmit live videofeed?
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Old Feb 09, 2008, 03:40 AM
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wedge98
there is a good guide to data rate here
http://www.jennic.com/support/view_f...eID=0000000078
The maximum data rate of 250kbs drops to about half this once various overheads are allowed for. The 250kbs also is shared between all devices on a given channel. There are 16 channels. If you try to use all the bandwidth on a channel that someone else is trying to use, it should still work but both systems will suffer. To be friendly to other systems I am trying to minimise the bandwidth I use. The XPS systems quote a max number of simultaneous users as 120 which is 7.5 users per channel. I'm probably using a similar proportion of the bandwidth. I doubt video is a goer. Looking forward to hear how you get on, give us a shout if you have any problems.
Alan

Correction - I just discovered that the xbee pros only have 12 channels so 120 users is 10 per channel
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Old Feb 09, 2008, 05:39 AM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
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Hi Allan

Speaking of xtremelink if an after market indoor rx could be a possibility im sure it would be welcomed.
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Old Feb 10, 2008, 06:19 PM
mem
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Quote:
Originally Posted by Alan Hopper
My dlg Alula has active angle of attack feedback and I am in the process of interfacing a playstation controller to the transmitter to enable me to send a whole host of extra channels to it to allow me to control control loop settings on the fly. Alan
Alan, I am very interested in what you are doing with your Alula. I am toying with the idea of modifying my Alula so it can be controlled using a wireless 3 axis mems joystick. I have a prototype using the wii nunchuck driving my PC flight simulator but have so far not had the courage or weather to try it with the Alula.

I am interested in finding more about what you have achieved with active feedback on your alula. Have you posted info on this somewhere?
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Old Feb 12, 2008, 04:03 AM
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Olmod
these modules weigh 2.25g so something around 3g is probably possible. The Meshnetics modules are smaller and lighter at 1.5g. The code for these would be similar using their openmac IEEE802.15.4 software. These modules are more expensive in the UK than the Jennic ones. I might get one to see if the jennic modules can communicate with them. To go lighter I guess you have to use just the chips themselves, does anyone know the legality of doing this in the UK on a diy basis?

Mem, I like the nunchuck idea, could be a challenge holding it still whilst launching though I put up a bit about my alula at http://www.rcgroups.com/forums/showthread.php?t=146767 I was just getting somewhere and broke the sensor, I then got convinced I needed telemetry, hence the 2.4ghz stuff.

Stunning weather has delayed things with lots of the old fashioned 35mhz flying. I finally managed to get the ps2 controller to work. When I first connected it up the module refused to boot. At boot time the flash is copied to ram over the spi bus at 16mhz, the module didn't like 6' of cable connected to the spiclk line, when I shortened it to 1' it worked fine.
Alan
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Old Feb 12, 2008, 04:24 AM
mem
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Quote:
Originally Posted by Alan Hopper
Mem, I like the nunchuck idea, could be a challenge holding it still whilst launching though I put up a bit about my alula at http://www.rcgroups.com/forums/showthread.php?t=146767 I was just getting somewhere and broke the sensor, I then got convinced I needed telemetry, hence the 2.4ghz stuff.
Alan
Thanks for the info. I do like your hitec rx mod, I use an HS-05s in my alula and it hadn't occured to me that I could use it as an onboard processor as well. Thanks!

The nunchuck has a switch under the index finger that I have programmed so that the TX ignores the sensor readings and just sends a neutral signal if the switch is pressed during launch.
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Old Feb 14, 2008, 08:29 AM
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It flies!
I just flew my alula for the first time with my ps2/jennic setup. I must be getting sad as I found it all very exciting! The ps2 controller will take some getting used to, luckily alulas bounce! Finger problems aside the control was rock solid.

mem, just give it a chuck

Alan.
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Old Feb 14, 2008, 09:05 AM
Good Better Best quest.
olmod's Avatar
Australia, VIC, Cranbourne East
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Quote:
Originally Posted by Alan Hopper
Olmod
these modules weigh 2.25g so something around 3g is probably possible. The Meshnetics modules are smaller and lighter at 1.5g. The code for these would be similar using their openmac IEEE802.15.4 software. These modules are more expensive in the UK than the Jennic ones. I might get one to see if the jennic modules can communicate with them. To go lighter I guess you have to use just the chips themselves, does anyone know the legality of doing this in the UK on a diy basis?Alan
mmm Dont know about English law regarding DIY Rx's but i would imagine any protection by JD would be in the micro processor programming, as he built the system on the foundations that Maxstream established ,he is an inovator ,he did not invent any origonal hardware concepts,but he did write some very good programming and put it all together i think before long you will see other MFG's like Corona Blue arrow ect making after market 2.4Ghz Rx's just as we have seen what happened to the common frequencies ,and i havent seen any system MFG's taking anyone to task over making after market Rx's .cheers
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Old Feb 25, 2008, 12:00 PM
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I have been experimenting with generating more than 2 channels of pwm with the jennic modules. This proved a bit of a challenge as the low level interrupts behave in slightly odd ways. I ended up writing a disassembler to discover what was going on behind the scenes! I now have it working and believe I can control up to 21 servo output channels with max jitter of 3/16 us with no extra hardware.

My next step is to finalise my board designs and make something more robust.

Got any any good ideas for the spec?

My thoughts so far
tx - make like a break-out board to provide easy access to all jennic ports

buddy lead interface
spi/playstation interface
usb programming port and single cell lithum charger so the whole thing can be built into psx controller.
LCD display
Auto powerdown (vital for 2yr old son!)

rx -
battery voltage monitor
stuff

Alan
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Old Feb 25, 2008, 02:24 PM
Impossible? Hah!
KreAture's Avatar
Oslo Fornebu, Norway
Joined Jun 2003
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Nice work Alan!
These modules probably use some 1mW all in one chip for the majority of the system.
I am trying to get something similar done with the nRF chips only smaller.

The nRF chips have 125 channels though, albeit only channels 0-83 are usable in all countrys. It looks like they calculate frequency like this: 2400 MHz + <channel> * 1 MHz. They can basically transmit on anything between 2400 and 2527 MHz.

How are you re-establishing link when the tx has started to hop but the rx has been cycled? I was thinking of doing a "marco-polo" sweep but there's a lot of channels to check...
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Old Feb 25, 2008, 02:37 PM
Inciting Riots
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Would a beakon channel be against the rules?
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Old Feb 25, 2008, 02:49 PM
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KreAture, these modules use a jennic chip that combines the radio with a 16Mhz 32bit processor (openrisc based). I have been thinking about making a smaller system using the jennic chip rather than the module, however the chip is bigger than the one you are using and requires external flash, but no seperate processor. I suspect your system is the way to go for small stuff. Do you know the legality of using just the chips rather than a pre approved module, on a diy basis?

I currently use a hopping sequence that will always resync within two cycles if it goes out of sync. At start up the rx can either pick a clean channel and only start hopping after the first received packet, or just start hopping and wait for auto resysnc. The sequence index is passed in the packet. An example of a self resyncing sequence is 1 2 3 2 1

Alan
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