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May 09, 2018, 04:46 PM
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How to use a FSK Modem Board


This is how to wire the FSK Modem PCB:


This is the above schematic applied to connecting a Omnibus F4 Pro board running iNav with the FSK Modem PCB and with the audio line from the VTX:


The correct setup matching the above wiring is activating LTM telemetry on UART1 with a baud rate of 2400.
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May 13, 2018, 05:38 PM
throw new IOPilotException();
IceWind's Avatar
Is there any alternative to the SMD FX604D4? Seems it is deprecated as well.
I'd like to make a TX module for my wings, but it needs to be quite small, in the ground a thru-hole is fine as there are no size limitations.
May 14, 2018, 10:39 AM
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Quote:
Originally Posted by IceWind
Is there any alternative to the SMD FX604D4? Seems it is deprecated as well.
I'd like to make a TX module for my wings, but it needs to be quite small, in the ground a thru-hole is fine as there are no size limitations.
I actually have that chip around here also because SMD stuff is always better then through hole (in my opinion). But the difficulty is that we set the tone pitch of 1 and 0 with resistors and the tone speed with a crystal. And none of them are standardized use at the moment, since a 4.433Mhz crystal is almost impossible to find. Meaning If you want to cross use them you will have to figure the values out. And if you just want to use that system independently then you still have to draw up a board. The FSK Modem v3 board is actually quite small though. There seems to be adequate wing space to hide such a chip in though. If you design something compatible with the existing system I'm def going to try it out also.
May 14, 2018, 11:29 AM
throw new IOPilotException();
IceWind's Avatar
Well I prefer SMD for size reasons. Smaller, lighter ...plan would be to set this on a 800mm wingspan wing (S800) that I'm cutting down on weight on anything possible to make it fly for as long as possible.

I see what you mean about the cristal usage, meaning that both ends would need to be using the same specs.
May give it a got and convert the FSK Modem v3 board to SMD and see how it goes. I'm no PCB export but should be ok as the part count is low.

PS: if cost + postage for those you have is ok I may get two to test. I'd like to make an mobile app to read the data.
Similar to what immersionRC has. That should pretty much FSK modem as well.
May 24, 2018, 02:15 PM
Registered User

How to quality check an assembled FSK Modem


There are 3 steps in checking if an assembled/soldered chip is any good:
  1. On the digital side connect an ftdi adapter, loop the O (out) audio with the I (in) audio. This way when typing something in the serial window at 2400 baud (or 1200 baud), the typed characters get shown real time in the serial window.
  2. Again ftdi on the digital side, but this time attach an audio speaker or earplug. Listen to the tone when there is no data and how it changes when transmitting data through the serial window. I'd prefer doing this method first as it also lets you know the strength (volume) of audio signal. But it's harder to perform as connecting an spear or earplug is not that easy.

  3. Again ftdi on the digital side, but now daisy chain two chips, connecting the O (audio out) from the first chip with the I (audio in) of the second chip. Then on the digital side of this chip connect R (receive) with T (transmit). And again the O (audio out) of second chip with the I (audio in) of the first chip. This daisy chain can be continued on the digital side also by connecting a third chip's R with the second chip's T and vice, versa. And then terminating that chip by connecting O with I. Or go for a forth chip. However there has to be a common ground in between the chips and each one has to receive the 5V power, for the chain to work.
    By doing this you know that the frequency of both chips match and the data can be transmitted-received/the pair is correctly working together.

And this is how I check the quality to be sure they perform. However till now I had none fail.
Jun 06, 2018, 04:27 AM
throw new IOPilotException();
IceWind's Avatar
@jelle737, what application are you using to receive/decode the LTM protocol?
Jun 06, 2018, 06:44 AM
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Quote:
Originally Posted by IceWind
@jelle737, what application are you using to receive/decode the LTM protocol?
The applications I have are:
*Recording DVR with a good DVR recorder knowing I can decode the data if needed.
*Using a tracker or something that uses LTM telemetry out of the box.
*Having this project to retrieve live data, to be used if needed. I would actually use this when I need to decode the DVR above.
*Having my personal project where one pilot should be able to see the other. But it's a work in progress.

And if you present an idea I have even more uses.

I actually do not have a pc running computer software program that can decode the audio or present the digital data in a nice format. That would be a cool project but my c++ skills that enable me to program .exe running in a command window does not allow me to play with COM ports yet.
Jun 06, 2018, 07:15 AM
throw new IOPilotException();
IceWind's Avatar
Quote:
Originally Posted by jelle737
The applications I have are:
*Recording DVR with a good DVR recorder knowing I can decode the data if needed.
*Using a tracker or something that uses LTM telemetry out of the box.
*Having this project to retrieve live data, to be used if needed. I would actually use this when I need to decode the DVR above.
*Having my personal project where one pilot should be able to see the other. But it's a work in progress.

And if you present an idea I have even more uses.

I actually do not have a pc running computer software program that can decode the audio or present the digital data in a nice format. That would be a cool project but my c++ skills that enable me to program .exe running in a command window does not allow me to play with COM ports yet.
Thanks.
I need to get something that records the details while I'm flying and is portable. So ideally it would be a mobile application.

EzGUI and iNav Mission as listed as supporting it but I can't find any documentation proving this claim.

MWPtools as well but that needs a PC, only in case I take my GroundStation with me and the laptop I'd be able to use it.
Last edited by IceWind; Jun 06, 2018 at 07:28 AM.
Jul 20, 2018, 09:37 PM
Registered User
Hi, using this module, I can't use a 5.8g audio to transmit a 2400bps signal, but a 1.2g image transfer system can be used for audio.
Jul 22, 2018, 02:57 PM
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Quote:
Originally Posted by dieyang129
Hi, using this module, I can't use a 5.8g audio to transmit a 2400bps signal, but a 1.2g image transfer system can be used for audio.
Both should work, both 5.8 and 1.2 (or even 2.4) video systems carry audio and can transmit a 2400baud signal, like LTM telemetry.
Jul 25, 2018, 02:03 AM
Registered User
Quote:
Originally Posted by jelle737
Both should work, both 5.8 and 1.2 (or even 2.4) video systems carry audio and can transmit a 2400baud signal, like LTM telemetry.
Thank you for your reply, I have solved this problem. But I use this module in ghettoproxy. After tracking for two to three minutes, the GPS coordinates of the ghettostation are no longer refreshed. I think there is a problem with the ghettoproxy code. I want to know if you have encountered this problem and can help me solve it. Thank you.
Jul 25, 2018, 12:11 PM
Registered User
Quote:
Originally Posted by dieyang129
Thank you for your reply, I have solved this problem. But I use this module in ghettoproxy. After tracking for two to three minutes, the GPS coordinates of the ghettostation are no longer refreshed. I think there is a problem with the ghettoproxy code. I want to know if you have encountered this problem and can help me solve it. Thank you.
The closest I got to ghettostation is by making my buddyOSD idea. But if there are problems inside that code I have no idea what they could be and what their solution could be.
You mean the GPS coordinates of the ghettostation itself, maybe it does not expect to move base after a few minutes?
Jul 25, 2018, 07:45 PM
Registered User
Quote:
Originally Posted by jelle737
The closest I got to ghettostation is by making my buddyOSD idea. But if there are problems inside that code I have no idea what they could be and what their solution could be.
You mean the GPS coordinates of the ghettostation itself, maybe it does not expect to move base after a few minutes?
I have a problem with my description
I use this 3105 module on ghettoproxy, which can send the GPS position back to the ground at the beginning. But after two or three minutes, ghettoproxy can no longer send gps positions, so ghettostation can no longer be tracked.
It looks like it is broken. If I just restart the ghettoproxy , it will work again for two to three minutes and then crash.
So I think the ghettoproxy maybe have problem
Oct 05, 2018, 02:23 PM
Registered User
Hi.
@jelle737, PM sent.
I`ll need some of your boards, if you have some for sale.
TIA, Norbert


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