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Old Feb 16, 2008, 11:33 AM
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The code in this project is for an 18F2550 it won't work in a 16C745 - whos / what code are you using to program the 16C745. I would suggest obtaining an 18F2550, programe it with either our code or Alessio's, change the crystal to a 4Mhz and give that a try.

PS its a bit hard to translate when you don't ask what you want to translate English into !
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Old Feb 16, 2008, 04:33 PM
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Hi Malc

Hi man

Thanks for all your input, i think you must be right about sending its pulse coded signals rather than pulse proportional and the refreshing timing.

As said it does work with the DX7 but only 1-2 sec and goes dead

Anyway glad to get it working with the futaba, i'll wait to more input to get it work with the DX7


Thanks again for all , nice project
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Old Feb 16, 2008, 04:52 PM
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Fred,

Hopefully one of the more experienced PIC programmers might chip in and suggest an answere. Alternatively, try programming an 18F with Alessio's code as his latest version supports PCM (I think) - You may need to alter the input pin for the PPM signals (Its been a while since I compared the two projects, and I'm knackered and wanting to sleep - so can be bothered to search at the moment !)
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Old Mar 01, 2008, 05:25 PM
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I have M&M's RC-USB8ch programmed and built up on a breadboard, but I am having a problem. It was recognized when plugged into the USB port OK but the LED did not stay on and there was no stick response when testing it in the Windows Control Panel. This was with my Futaba 6EXA (in PPM mode). I re-checked the signal-in circuit several times, etc.

Then I tried my old (and gold) Futaba FG Series FP-T6FG and it worked! Hooking up a scope to the base of Q1 shows the expected pulse pattern at about .4v for both transmitters. Six channels for the 6EXA and actually 8 on the FG. Apparently it was made as an 8 but only 6 were made functional. I have attached pics of both.

So, any ideas why the 6EXA doesn't work?
Thanks,
Jeff
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Old Mar 01, 2008, 05:44 PM
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Seems to echo the same issue Fred was experiencing in this thread http://www.rcgroups.com/forums/showthread.php?t=568806

Have you tried using Alessio's NG2 code and testing with both TX's.?

Looking at the traces they look very much the same in amplitude etc, so can't think what may be happening. I'm hoping Mark, Mr RC-Cam or one of the other contributors could chip in here and comment. Maybe there is something in our original code that needs tweaking to tollorate whatever it is that is failing.

If it was the 6ch TX that worked and not the 8 then I would of said it was a time frame issue, but as its the other way round this has me stumpped !
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Old Mar 02, 2008, 08:32 AM
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Malcolm,
It does seem like a similar problem to what Fred experienced.

I have not tried Alessio's NG2 but will plan on building it up and see what results I get. Should be interesting...

I will also do some more probing around with the scope and look for any possible differences.

Thanks,
Jeff
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Old Mar 02, 2008, 04:00 PM
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Problem solved! It turned out to be the apparently not-so-equivilant transistor I had used.

When building up the NG2 I just moved over the 2N3904 I had used in my M&M build, and had similar results. The old Futaba FG worked but the newer 6EXA didn't. The 2N3904 was listed as being a cross for the BC550C.

So then I went with a BC107 as listed on Alessio's schematic (which I had) and it worked for both builds! I then also tried a 2N2222 and it worked just fine too.

Back to the scope. As I mentioned previously the amplitude of the signals at the base of the transistor were the same. But, at the collector/pin 21 of the pic there is a difference. With the BC107 it is 4.9v with both transmitters on both builds. With the 2N3904 it is 4.2v (FG) and 2.8v (6EXA) on the M&M build. On the NG2 it is 3.8v (FG) and 1.7v (6EXA).

I looked at the data sheets for these transistors but I don't know enough to tell what might cause the difference.

At least it made me get out and play around with the scope again. It's been fun building these up, and I might even use them with a simulator now!

Jeff
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Old Mar 03, 2008, 11:38 AM
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Jeff, that's excelent news, and thanks for some extensive testing with the scope. Looking back at my notes, the original schematic was for a BC547, but as I didn't have one I used a BC550, which worked with my JR and Fitaba TX's.

My guess is that by changing the values of R4 & R5 when using the 2N3904 or BC550 may result in higher voltages at pin 21 of the PIC.

I'll edit the first post to recommend the use of a BC107 or 2N2222 rather then the BC550
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Old Mar 04, 2008, 06:49 PM
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Malcolm,
I found that I had a BC547 so just for fun I tested it out too. Worked just fine with both builds and my transmitters. This project has fired up my interest in electronics again. Thanks for everything!
Jeff
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Old Mar 05, 2008, 11:09 AM
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Jeff,
Thanks for the feedback. It looks like my original substitution caused this fault, but I'm glad to of fired off your interest again
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Old Mar 13, 2008, 03:05 AM
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Hi guys,
Sorry fgor not been around at all for what seems like 20 years, but lost my info, and took me ages to get things square again.

Will keep track of whats going on so will try to help again if at all possible!

Mark
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Old Apr 16, 2008, 12:12 PM
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DX7 Signals

I just took a look at the output of my DX7. Its PPM and about 22mS cycle time.

However, its only about 1.4 Vpp and apparently AC coupled. With the DX7 output connected to the direct coupled scope (10 Meg impedance) the signal goes between +.4 and -1.0 V. The levels are determined by the duty cycle of the signal. That probably explains why it could work for a few seconds (while the coupling cap gets charged) then quit.


I believe the input circuit will need to be revised. A simple diode (Schottky?) clamp might be a solution.
The PIC and XTAL for my NG2 should arrive today so I should be able to take a closer look.

Can anyone comment on whether or not the 22mS time should be OK?
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Old Apr 17, 2008, 04:08 AM
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for Andy... answered at:

http://www.rcgroups.com/forums/showt...=568806&page=3
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Old Jun 26, 2008, 07:50 PM
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I built this fine device however I can only get it to function with the NG2 4 axes code.

A&A code for 8 axes only returns "Unknown Device"

M&M Code does not work at all, WinXP does not see anything.

I tried recompiling with a few different options to no avail.

I can recompile the 4 axes A&A code and it works fine, or the original.


The only difference is im using a 4Mhz resonator instead of a crystal, shouldnt matter as XT type osc is setup in config. I did try with HS osc just in case but still nothing.


Any Ideas?

Thanks!!!
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Old Jun 27, 2008, 01:45 AM
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Quote:
Originally Posted by Jappa_Indy
I built this fine device however I can only get it to function with the NG2 4 axes code.

A&A code for 8 axes only returns "Unknown Device"

Thanks!!!
quite strange.... anyway the difference between 4 axes and 8 axes is that 8 axes is a full speed usb device.... (then requires at least USB 1.1) while 4 axes is a low speed usb device.... what kind of hardware have you build? for 8 axes check you have not mounted the resistor between VUSB and D-

check also the cable... if you used a very old cable.... anyway if you can try to change it...

alessio
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