Using ASF in other transmitters...

[HaCo]

Hallo jungs,
Hier auf bit-racer.de wird auch viel gebastelt, vieleicht is dies eine gut idee, ich habs auc so gepost auf minizracer.com forums...

Since last week I'm a proud owner of an EX-1UR with ASF module (RF-901SM). Before I had the KT-18, with the known throttle problem.

I remembered seeing pics of the inside of the KT-18, which looked quite simple: some buttons and small components combined with a big module that does all the hard 2,4GHz work.

Now, I had a tip from one of my Z buddies, who told me that you could remove the physical antenna of the EX-1UR module (RF-901SM), just by placing the wire of that antenna in the module. It was an easy fix, so I opened the case and did the job. But, surprise, surprise: inside the module, there was another module that looked quite the same as the KT-18 module.

So I started unscrewing my KT-18 to have a peek inside, here are the images:






The module (RF-901SM) inside looks like this:






This is the big module where I'm talking about, the KTSS-701, which is in both the KT-18 as in the RF-901SM:


I wonder if this could give us some opportunities. I have my EX-1UR now, which was quite expensive, but would it be hard to modify a regular transmitter to use the module?

I think it should, the easiest way to do this, is to use the complete RF-901SM, why is that easy? Because it is already done in for example the Futaba Tx, simply by rewiring the pins or using the PN adapter.

But, if it would be possible by using the KTSS-701 module, it would give the opportunity to re-use the KT-18 Tx components, which will be eating dust anyway when its KTSS module is used in another Tx.

The theory you need to know is that in a Tx you have path from your fingers to the transmitter. Your finger sets a position on a pot meter. A micro controller with some A/D controller in it will code the signal to something like PCM. This micro controller will also trim your steering in case of a digital Tx, it would also add a logarithmic feeling to your throttle if you have set this up,... but the most important thing is that it codes this signal something like PCM.
This PCM signal is then modulated to an RF signal and put on an antenna, that could be AM, FM, on 27MHz or 40MHz or in the case of ASF it uses DSS on 2,4GHz.

I think in case of the KTSS module, the coded signal is presented at it signal ports and the KTSS module only modulates the signal.

So if you would be able to extract the coded signal from an old digital Tx and send it into the KTSS module, then you have a converted digital Tx with ASF.

I'm not saying I will be able to do all this, I'm just saying it could be interesting for some of us the find a cheap way to convert an older digital transmitter (like the Futaba 2PL) with the KTSS module.

What you guys think? Maybe some experience, some tips to help me on the way? Anything is welcome.

Here's another informative site:
http://www.mini-z-guide.com/radio.htm
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[microsash]

Hi !

The Module in the KT18 and the Ur Module is the same.

But on the mainboard of the module is a converter chip, so there is no easy build from one to the other.
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[HaCo]

You probably mean the chip between the KTSS module and the connector to the Tx?


By HaCo

It's a Microchip PIC16F688, which is a microcontroller with some analog ports Would they have protected the code inside?

I think I will start my approach analysing the KT-18, if you take the third pic of the KT-18 there is a black square on the upper left corner. Wonder what that device is.

Urgently need a scope!!
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[HaCo]

Very quick analyses of the two images of the RF-901SM:
- PIN1 of CN1 goes to PIN11 of the PIC, which could be an ANalog or INTerrupt input I think.
- PIN5 and PIN6of the PIC go to the KTSS module. PIN5/6 are RC (digital) ports, or Rx/Tx of serial data, which could make things very complicated...

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[microsash]

The PIC is not the problem......the problem is the code on it....
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[Tanis]

the question is: Is the CP-Fuse (Code Protechtion) set in the PIC. If not, ist possible to read out the PIC and make multiple copys.

Regards

--- Lars ---

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[HaCo]

Hi guys,
I've been playing around with my multimeter to get to know the KTSS module better.

What I learned today about the KTSS module:
- It works on around 3V (KT-18 as 3V regulator, RF-901SM uses 3.3V regulator).
- The pairing key and LED are directly connected to the module, on the same pins and in the same way on the KT-18 as on the RF-901.
- In the KT-18 the position of the throtle and steering is directly send analog from both the pot meters to the KTSS module. Also all the trimbuttons are connected with the KTSS module.
- The big Square on the left of the third pic of my first post is nothing more than a stupid zoomer
- The RF-901 uses different pins to send position of throtle and steering (and other channels maybe?), it is coded and send over 2 pins. Unfortunatly I wasn't able to create a clear image with JOsci, but I will try to get an osciloscope from work. I hope its a simple PPM signal
- Found out that some of the SMD resistors on the RF-901 print have value '0', I bet this means it is used to jump over other traces on the PCB

Any ideas are welcome...

Btw, if anyone has a Minium plane and wants to open the Tx to see if it uses the same KTSS module, would be more than welcome to show here.
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