Interfacing TM-002 module

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joloom
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Interfacing TM-002 module

Post by joloom »

Hello all,

First of all thanks a lot for giving me the chance to place some specific questions related to 9X 2.4 GHz RF module.
I am intending to build my own tiny remote control (our 4 little kids are pushing heavily...).
30 years experience in embedded control programming and electronics is given, especially related to ATMEL microcontroller applications - so that's not the issue.

I have ordered via Hongkong one 2.4 GHz TM-002 transmitter module and 1 receiver each with 3, 6 and 8 channels.
Then I checked hundreds of posts in several internet forums collecting a lot of information.
Nevertheless there ae some open remaining questions:
  • I have found the following TM-002 connector pinout: 1: PPM, 2: 6V DC, 3: Batt V+, 4: GND, 5: RF out - can anyone confirm this?
  • According to TX9 schematics only GND and pin 3 (Batt V+) are connected to power supply. Is pin 2 (6V) providing the voltage from the module's voltage regulator?
  • In some applications I've seen the RF module gets supplied with 5 V only. What is right? Does it need 12 V (or 11,1 from 3S LiPo) or is 5 Volt sufficient?
  • The bind algorithm to connect transmitter and receiver: is it exclusively implemented in the module or is also the transmitter ATMEGA taking care of binding?
  • My idea is instead of a typical RC PPM signal to use the TM-002 module to transmit a binary code pattern every 5 ms similar to a RS232 protocol - has anyone of you experience in trying such thing?
  • Accordidng to the information I found on the WEB only the 6 channel receiver is providing a summary signal. Is this right? Or is there also a summary signal available in the 3 and 8 channel receiver? (it does not have to be available on a connector pin - I can take it from the PCB)
  • In the WEB I have only found the confirmation that it is possible to bind TM-002 with the 6 channel and 8 channel receiver. Does anybody know whether the small and cheap 3 channel receiver can also be bound?
Any kind of answer would help me a lot. It will still take up to 4 weeks until the Hongkong delivery arrives - so I currently have to focus on preparation stuff...
Unfortunately I haven't got a TX9 so I am unable to take reference measurements.

Thanks a lot for your help!
Johannes

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GrootWitbaas
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Re: Interfacing TM-002 module

Post by GrootWitbaas »

Ok lets see what I can answer for you :
  • I have found the following TM-002 connector pinout: 1: PPM, 2: 6V DC, 3: Batt V+, 4: GND, 5: RF out - can anyone confirm this?
    Not sure but sounds correct
  • According to TX9 schematics only GND and pin 3 (Batt V+) are connected to power supply. Is pin 2 (6V) providing the voltage from the module's voltage regulator?
    In the module there is a Vreg, and I think from memory V+ and "6v" are connected to the output from a 7805
  • In some applications I've seen the RF module gets supplied with 5 V only. What is right? Does it need 12 V (or 11,1 from 3S LiPo) or is 5 Volt sufficient?
    5v is fine, it has a 3,3v vreg on board
  • The bind algorithm to connect transmitter and receiver: is it exclusively implemented in the module or is also the transmitter ATMEGA taking care of binding?
    Done by module
  • My idea is instead of a typical RC PPM signal to use the TM-002 module to transmit a binary code pattern every 5 ms similar to a RS232 protocol - has anyone of you experience in trying such thing?
    Not me .... but I think it needs ppm ...should look at frsky instead (or some other rf links)
  • According to the information I found on the WEB only the 6 channel receiver is providing a summary signal. Is this right? Or is there also a summary signal available in the 3 and 8 channel receiver? (it does not have to be available on a connector pin - I can take it from the PCB)
    For 6 it's on the older ones, on 8 there is nothing, I checked with scope. never had a 3ch in my hands
  • In the WEB I have only found the confirmation that it is possible to bind TM-002 with the 6 channel and 8 channel receiver. Does anybody know whether the small and cheap 3 channel receiver can also be bound?
    You get 3,6,and 8ch ....they will all bind
Now the problem is they use closed (proprietary) firmware on the TX/RX so I'll suggest you look at something like the frsky or xbee or something supporting serial. I wanted to look into doing something similar, but saw this way will not work, and never went further. (I have been proven wrong thou)
General trouble maker and wannabee Dev
joloom
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Re: Interfacing TM-002 module

Post by joloom »

Thanks a lot for your information - it's helping me a lot!
Now I simply need to wait for the delivery of the modules. I am still hoping to find summary signals being available on the receiver boards.
Usually I am connecting own Atmel microcontrollers just reading one single summary signal instead of several discrete channel pulse signals. Makes life easier.

In terms of supply voltage I am still wondering why TX9 is using a 12 V battery because I have not found any need for it in all schematics.
My intention is to supply the device with a 2S LiPo (7,4V). That's more than enough to create stable 5 V. In worst case I simply need to replace the 5V voltage regulater in the RF module by a low drop type.

Cheers
Johannes
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gohsthb
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Re: Interfacing TM-002 module

Post by gohsthb »

the 9x uses 7805 type regulators that specify 2 volts dropout voltage. So you would need to supply at least 7V without changing the regulators. Having a 12V battery is a leftover from 72MHz or 35MHz modules. Those needed the higher voltage.
-Gohst
joloom
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Re: Interfacing TM-002 module

Post by joloom »

Thanks Gohst - good to know where this solution is coming from.
Translated this means: Every TX9 user is carrying 50% battery weight just to use electric power for environmental heating. Or: a waste of 50% operation time using the same battery weight and size. Strange...
Checking the schematics for TM-002 being available in the WEB it even seems to be possible to fully operate TX9 transmitter with a single cell LiPo 3,7 V. This would result in trice the operation time assuming same batt size and weight. Of course it would require some component replacements e. g. for LED resistors etc. But the main microcontroller and the HF module are able to run on 3,3 V.

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gohsthb
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Re: Interfacing TM-002 module

Post by gohsthb »

The main controller operates at 16MHz. an atmega64 can only operate at that speed above 4.5V.
-Gohst
joloom
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Re: Interfacing TM-002 module

Post by joloom »

Hi Gohst,

You are fully right - as long as you stay with the given software and the 16 MHz crystal this would be a project killer.
Nevertheless: if anybody realy aims for converting the transmitter to 3,7 V supply there is clearly a chance.
It simply would require to lower the system clock (I would need to check the data sheet - probably 12 MHz would be sufficient) and to modify the relevant timer settings in the software accordingly.
I rarely experienced in any of my previous RC embedded control gimmick developments any problem in terms of prcessor load. Most likely because the majority is written in assembler anyway. But even for the TX9 system software I don't see any obvious reason why it should not fit to a slower processor speed. In worst case it would require to write time critical sections as embedded assembler code with some optimization towards processing time.

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gohsthb
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Re: Interfacing TM-002 module

Post by gohsthb »

Following the slope in the graph you can run 12.4MHz at 3.7V. However if you only have 3.3V you can run a max of 10.6MHz. That's a lot of speed change over a very short voltage span. I think you might be limited to 8MHz to run the lower voltage.
-Gohst
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MikeB
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Re: Interfacing TM-002 module

Post by MikeB »

The PPM, PXX and DSM interrupt routines are already critical at 16MHz, they would not work at a slower speed. In particular, I think the PXX uses up about half the processor time while it is sending data, so at 8MHz you wouldn't have any time left for anything else.

Mike.
erskyTx/er9x developer
The difficult we do immediately,
The impossible takes a little longer!

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