HK GT2R module hook up.

Like B&Q for homebrew radios
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

HK GT2R module hook up.

Post by MaxZ »

MaxZ wrote: 25 Jan 2020, 18:15 Hi,
Does anyone know if and where I could buy a FlySky FS-RM0002 module? I have a bunch of HK GT2R 3 channel receivers operated with the AFHDS protocol, and a cheap pistol grip Tx, and I want to convert an old Robbe 2 channel Tx to 2.4 GHz. ( no Phil, not the same one ;) ) I looked into butchering the pistol grip Tx and extract the HF board, but it is intimately mated with the main board, and the connections are not identified afa. I can see.

Cheers,
Max.
Right, in the absence of any reactions on this post in the FlySky RM-FS0002 topic, and on a similar question in the Dutch forum, I am still stuck acquiring a module with AFHDS protocol. So I decided to butcher the pistol grip Tx after all. I had to desolder the antenna, which is quite tricky, so hopefully I can get it soldered on again without failure.
The salvaged module appears to run on 5V, and as my supply is a 2s lipo, I need to install a regulator of sorts. Would it be possible to tap the regulated supply of the DigiSpark board, or would that be over-stressing the regulator?

Cheers,
Max.
Mosfets
Posts: 60
Joined: 18 Feb 2018, 20:14

Re: HK GT2R module hook up.

Post by Mosfets »

Sorry I meant to reply to your post.

Following your post I looked for the module but it seems to have disappeared off websites.

What I was going to suggest is to canibalise a FS CT6B transmitter for the module. Ebay seems to have a few secondhand and plenty of new available.

Hope you get yours working.

Ade
User avatar
Phil_G
Posts: 597
Joined: 15 Feb 2018, 23:32
Contact:

Re: HK GT2R module hook up.

Post by Phil_G »

Not tried it Max but the standard DigiSpark has a 1A regulator so should run the module ok ;)
Try it, see if it gets warm... :D
Does your module look anything like the one inside the RM002?


Image
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

It does Phil, at least it is also a "tin box" but it has only 6 connecting pins opposite the antenna connection. But before I dislodged it from the main board, I powered it up, and measured the voltage of the pins. The top two are the same, 0V and 5V, but the next one measured about 3.5V, which I guess is the bind connection. How is it normally connected, via a button to GND? The other 3 pins all measured 0V. Luckily, the main board did not get destroyed, so I will be able to measure which one the ppm is connected to with the pulse analyser.
It will be a bit of an adventure.

Cheers,
Max.
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

Measured the voltages again, with the HF board removed this time. It appears that the #5 pin also measures 3.5V
I tried to wring a ppm from the main board as well, no sign of anything I am afraid. Also checked if depressing the bind button showed any change to the voltages, or to the resistance to gnd, again nothing. This is not good :roll: :cry:

Max.

Edit: I can detect connections to the processor on the main board for pins #3, #4 and #6, all the pins that do not show a voltage, whatever that information means.
Last edited by MaxZ on 29 Jan 2020, 10:42, edited 1 time in total.
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

MaxZ wrote: 28 Jan 2020, 20:21Edit: I can detect connections to the processor on the main board for pins #3, #5 and #6,
I have to correct that to #3, #4 and #6, measured voltages are on the picture below (0 if nothing shown)

I did not think it necessary to connect the pots while testing for a pulse before, but today I salvaged them from the donor Tx, and connected them. It did indeed make a difference, now I am seeing some pulses on #3 and #5. However, these are very erratic, sometimes only one channel, sometimes more (up to 4). Moving the pots does not result in anything noticeable.

From studying the pcb, I can conclude that #1 is definitely GND, #2 most likely 5V supply, and #4 seems completely isolated. And #3, #5 and #6 are connected to the processor.

Fwiw, overviews of the main board:
DSC03960.JPG
DSC03962.JPG
Details of the module connections:
DSC03966.JPG
DSC03964.JPG

Cheers,
Max.
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

I have a small scope, so I captured the pulses on pins #3 and #5:

#3:
DSC03968.JPG
#5:
DSC03969.JPG
DSC03970.JPG
DSC03971.JPG
It does not look like a standard ppm stream to me, maybe serial communication?
#5 is closest, but the pulse width is way too short, and there is this long High.

None of them showed any difference while moving a stick pot.

All not very promising :(

Cheers,
Max.
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

Phil_G wrote: 31 Jan 2020, 12:29......if thats a full frame......
#3: full frame 0.9 ms, burst 0.7 ms
#5: full frame 0.9 ms, burst 0.25 ms (excluding the prolonged high pulse)

Viewed at a wider timescale, it looks to me like not all bursts are the same, so it could be serial data transmission. I cannot detect a beginning and end of a packet though (not sure if that terminology is correct).
DSC03972.JPG
Cheers,
Max.
User avatar
Mike_K
Posts: 669
Joined: 16 Feb 2018, 06:35
Location: Hertfordshire

Re: HK GT2R module hook up.

Post by Mike_K »

Max

The resolution of your oscilloscope is not high enough to determine what type of signal it is. Many modules use SPI to communicate with the 2.4GHz chipset or if there is some logic in the rf section, then a protocol based on s-bus is popular with many Chinese sets.

Have you thought of getting a cheap logic analyser? The Saleae clones are under €10 from China and the software is free and quite intuitive. Below is a link to the seller I bought mine from, but on the Dutch eBay site

https://www.ebay.nl/itm/USB-SALEAE-24M- ... Sw89Fc57Bb

It software has an Analyzer and Protocol Decoder, so you can automatically detect if it's asynchronous serial, I2C, SPI etc and can "auto-select" the baud rate for serial.

The only problem is they say they ship from the UK, but they don't, mine came directly from China. So there could be a bit of a delay with their new year holidays and the travel restrictions within China due to the Corona virus.

Mike
MaxZ
Posts: 330
Joined: 31 Jan 2019, 11:48
Location: Boskoop, Netherlands

Re: HK GT2R module hook up.

Post by MaxZ »

Hi Mike,

Thanks for the tip, I will consider to buy one of those. But knowing the protocol is one thing, creating the matching signal is beyond my capabilities I am afraid.
Regarding my little conversion project, it is a passed station anyway. The objective of using the module I salvaged was to continue the GT2R receivers with the AFHDS protocol. As I said before, the Turnigy/Flysky i6 Tx's are capable to transmit that protocol (besides the AFHDS-2A protocol), so my friend decided to buy one of those.
I wil continue with the conversion of the old Robbe Kompakt, but with a different module, probably a FlySky FS-RM-0003 (same as I use in my s/c Tx based on your sketch), which I know works with ppm. As I found out in the past with the help of some others, I only need to convert the sketch to negative pulses, but in this case it is simply swapping two high and low settings.

Cheers,
Max.
Post Reply