sim cable

[Lewist]

I bought an esky honey bee helicopter a week ago which came with a sim cable for the transmitter and a few little bits of software to make it all work.

the sim cable has a a mini din on one end that plugs into the tx and a serial connector on the other, it is a double sided connector with a little serial connector on one side and a large serial connector on the other.

If i connect it all up using the little serial connector (all my pc has) and turn my tx on the serial reading progam sees the pcm signal but it apears to be all garbled, like it is corrupted.

it has two little squares with dots in that represent the position of the sticks, these move randomly and are not really affected by the TX.

I am running windows XP

any help on this would be greatly appreciated!

[aeropal]

...

[Lewist]

ok i have read it but its not meaing a great deal to me!

[Malc C]

There is a lot of information in that thread you have been referred to, and it can be information overload if you are not too familiar with the terminology.

There are two ways of transmitting data via the buddy box lead connector (the mini din plug on your TX). PCM and PPM - most TX's use PPM, but a lot of the Piccolo / Hummingbird clones use PCM. Have a look on the RC-Electronics.co.uk website (second url down on the second post on the referral thread) for prices but here's the explanation

This transmitter outputs a serial data signal from the 4 pin mini Din PC interface on the back of the transmitter. This serial data signal is not compatible with FMS.

Their Zhen-hua PCM interface resolves this by:

The Zhen Hua PCM-4CH Interface is a special interface just for this transmitter which converts the data signal into a standard FMS PIC serial (9600 Baud) format, making it work with FMS under all versions of Windows OS including XP.

However, you really need to confirm that the e-sky is outputting PCM signals and not PPM signals, and for that you will need to download the windows soundcard ocsilloscope from http://polly.phys.msu.ru/%7Ezeld/oscill.html. The signal should be coming from pin 1 as shown on the image below

[Rickenbacker]

If your sim supports joystick control you can use PPJoy to convert your serial stick input to joystick signals that the sim can read. Can't remember where to get it offhand, but do a search for it.

[bluesky123]

Malc C,

Please don't call Zhen Hua protocol as PCM, it has nothing to do with PCM!
The only currently (or recently) built Chinese transmitter, which employs Zhen Hua protocol (only for exchanging data with a PC, the RF signal is still a PPM compatible with regular PPM or FM receivers) is 4-channle Walkera. The manufacturer of helicopters/transmitters sold under the names of ESky, E-flite, Twister, etc., has never (or, at least, in the last couple of years) used Zhen Hua protocol! Even Walkera is switching to the "normal" PPM signal in their trainer/simulator connectors.
So, let's forget about Zhen Hua in order not to make things even more complicated.

ESky and Walkera connectors use different wiring of the same mini-DIN (S-Video) plug. That's may be the reason why a cable, which works with one brand, doesn't work with the other.

Also, it is necessary verify that the interface is not just a straight 4-wire cable simply connecting the pins of mini-DIN plug with 4 of the pins of the serial connector. Such a cable only orks with transmitters implementing Zhen Hua serial protocol, which are not beeing made any more, AFAIK. Just open the hood of the serial plug and check if there's a circuit board with a microchip there.

Boris

[Malc C]

Boris,

I beg to differ - here is a quote from an e-mail I received from RC Electronics when they were developing their interface for the Zhen Hua TX.

Not only is the output signal data, rather than PPM, it is sent in a
"reversed" bit-order and, if the Tx is powered by its own batteries, the
data rate is really weird (slow) - I don't think that any PC com port could
deal with it.
This is presumably done due to the limited bandwidth of the FM signal
transmitted to the model - it could not transmit data any faster.
We discovered that, if we kept the Tx switched "off" and supplied power to
the coder chip via the interface, the chip runs at 19200 baud.
We rewrote the PIC code to take this data, put it into the correct order and
output it at 9600 baud, as in our regular FMS interface.

I don't think that I would hold my breath for the 6 channel version!

Regards,
RC-Electronics (John).

Aeropal also referred to a previous thread where with Rissy's help, we proved that the transmitter that comes bundled with the new Hummingbirds follows tradition and outputs PPM via the buddy box connector (also a mini - din) and not the Zhen Hua format.

I think that the main crux of the problem is that manufactures do not stick to one standard, so one uses pin 1, others pin 3, or pin 4, etc, so whilst we found what works for the Century Elite 4 TX, it may not work with the TX that comes with a Twister, simply because the Twister's TX transmits the data on, say pin 3 for example, of the mini-din. This is why I suggested the use of the windows scope software to confirm a) if a PPM signal is being sent, and b) on which pin. - Saves ripping the guts out of the existing cable !

[Lewist]

Hi

Ok i have tested the signal from the tx.

I am getting a signal out of my pin one but it doesn't look like the singal posted in the other thread.

There is also a large circuit board inside the serial plug!

[Malc C]

This is what I would do if it was me.

If its possible to see the PCB in the plug, and you can see the wire coming in from the cable that plugs into the TX, then use a test meter (or a simple continuity tester made from an LED and 1.5v battery) and with one end of the test lead touching the cable that is soldered to the PCB, touch each pin on the mini-din plug until the LED lights or the meter deflects or registers a short. This will verify that the interface is expecting to see a signal on pin 1.

If you find that it uses a different pin then use the scope software to see what trace you get on this pin, hopefully it should be similar to the normal trace shown on the other threads.

[bluesky123]

I beg to differ - here is a quote from an e-mail I received from RC Electronics when they were developing their interface for the Zhen Hua TX.


Malc C,

What does your quote has to do with PCM?

Zhen Hua protocol is just another propriatory protocol, which bears little resemblance to PCM!
Here's a good description of both PPM and PCM:
http://www.aerodesign.de/peter/2000/PCM/PCM_PPM_eng.html

Chinese R/C manufacturers have made it difficult to figure out how to use their products. Don't add confusion by throwing in irrelevant information.
:)

Boris

[Lewist]

malc c

there are two wires that connect to the pcb in the plug.

I have tested all the pins on the back of the TX and this is the only one i get a signal out of.

[Malc C]

Boris, Like I said it was a direct quote from an e-mail I received from one of the leading interface suppliers in the UK. The first line states that Not only is the output signal data, rather than PPM, it is sent in a
"reversed" bit-order so the assumption was that if it's not PPM and its sending signal data in a reverse bit word format, then it's sending some form of pulse coded modulation.

The fact that it may be no where near the true definition of PCM as definned by that link you so kindly provided, is neither here no there. The fact that the Chinese RC manufactures seem to come up with their own bespoke communication mode does indeed make thier products difficult to function with "standard" (if there is such a thing as Standard) western components. - On that I will agree with you :)

[Malc C]

malc c

there are two wires that connect to the pcb in the plug.

I have tested all the pins on the back of the TX and this is the only one i get a signal out of.

Boris,

Can you shed some light on this (seeing that I've obviously got the wrong end of the stick over PCM). Lewist has provided a screen grab in one of the posts above of the output from the TX's buddy box port. It is nothing like the normal rectangular signal you would expect from a PPM signal, and looking at the captured image he has had to have the gain fairly high to obtain that trace. The trace does seem to be repeating itself and have some degree of channel definition.. care to offer an opinion so we can try and sort this out for Lewist

[Lewist]

Malc C

the tx is a ppm tx.

It says so on the tx, the rf module on the back, on the instructions, and on the rx unit in the heli!

would you like a picture of the inards of the serial plug? there is a little micro chip (20 pins as i seam to remember (i closed it all up again) a resistor, a capacitor and a few small surface mount componants (probably resistors, caps and diodes).

there also apears to be power coming from pin 3.

one wire goes to pin one (the signal) and the other wire to the outer sheald of the DIN plug.. but that doesn't connect to the outer part of the serial plug!

[Malc C]

That chip is probably a PIC microcontroller, a picture may help to identify it, but beyond that it won't really help much. Possible things that may or may not have an impact

1) the serial port on the PC is not seeing the device
2) the interface is faulty
3) the TX's buddy box port is faulty and is sending corrupted signals
4) the software is botched and simply fails to recognise the signals.

Do you have another PC you could try, or try it on a friends PC that has windows 98 or ME /W2K running - this would identify if its your PC and / or OS that's the issue rather than a faulty interface.

Did the cable come bundled with its own version of flight sim ? - It may be that the device will only work with that bit of software (clutching at straws here :) )

Other than that, I'm at a loss. The only thing I did notice was that the level on that scope software had to be turned up rather more than when I was capturing the input from my JR X3810, which suggest to me that the signal simply is not beeing transmitted with enough amplitude for the interface to detect it, which is why it ain't working. Does the signal change if you turn the TX on or off ??

[Lewist]

Malc - before i start, thanks for your help!

I have tried it on both my work and home PCs with the same effects on both computers.

I will try it on an old pc at work with an older os and see what happens.

the heli did come with a cd, but its all generic stuff. there is ppjoy, pic serial interface thinggy and two version of fms, an older and newer version!

when i turn the tx off, the signal stops.

thanks

Lewis