DIY-Multiprotocol-TX-Module
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pascallanger
Volantex Super Cub V765-2
This model is using Volantex radio with 5 channel receiver EAR403. Is it possible to bind multimodule to this receiver? The V761 protocol does not seem to work on 4-CH mode, maybe this EAR403 is a different kind of a sub protocol, or maybe a different protocol?
No idea... I can't even get a picture of what the original radio looks like. Do you have the radio or only the receiver?
I've found this link: https://fr.aliexpress.com/item/4000847736638.html Are you sure it doesn't bind to the V761 protocol since the TXs look exactly the same from outside?
Hi Pascal. This is the receiver And you can find the transmitter on the same page as EAT 403, the description is wrong, as it is a 5 channel transmitter. It has extra switch on the left rear side, and it is driving the 5-th channel you can use for whatever function you want. The switch on the right is the gyro Easy-Normal-Expert function switch.
I have tried V761 several times with different TX id's, with no luck on binding. So I think it might be a little different transmitter/receiver combo, mainly due to the spare 5-th channel. Your Ali link is good, as the receiver is in 2 versions - one with plastic case, and the other without. My plane has the version without the case. The transmitter for V761is EAT 402.
Do you have the radio or only the receiver?
I have them both, the receiver is glued in the plane, but it is the one you linked from Ali. The transmitter looks exactly the same from the outside, but EAT 403 has extra 3 position switch on the left. There is no EAT 403 or other name on it.
YouTube, look at 1:57 It seams that this is a new version of 765-2, the older one was shipped with the Volantex transmitter with channel reverse buttons on the front. The new version has the gyro.
Do you have an internal or external module? Do you have a logic analyzer? Can you do a picture of the radio internal and more specifically the chip(s) near where the antenna is connected.
External URUAV TMX5 Lite on Taranis X9 Lite. I have Saleae 8 channel clone. I can do the picture. Will try tommorow.
Sounds really good! I'm thinking that you can hook your logic analyzer to the SPI bus and do some dumps. If you know what you are doing then go ahead and post the dumps.
Great, on the last picture we see the signal names. You want to connect these to your logic analyzer: From top to bottom on the last picture:
- SPI_SS -> analyzer port 1
- unconnected -> unconnected
- GND -> anaylzer GND
- RST_N? ->analyzer port 2
- MISO -> analyzer port 3
- SPI_CLK -> analyzer port 4
- MOSI -> analyzer port 5
- 3.3V -> unconnected
Then start a dump before powering up the radio then quickly power the radio so we can see it booting. Is that enough guidance for now?
If you know how to do it then sure add a SPI decoder and point it to the different signals: SPI_SS (CS), MOSI, MISO, SPI_CLK (CLK). Set the sample rate to 10M to start with. We will surely need plenty of dumps so getting used to add the SPI would be good. Share the full dump with the SPI decoder configured. Not just the output of the decoder.
I have no 10MS rate, so I've choosen 12MS. Here is the 10s dump of the start sequence of the transmitter. 12 MHz, 120 M Samples [1].zip I think, that the clock line is not configured right with the default settings. There is a message in the export file
Time [s], Analyzer Name, Decoded Protocol Result
0.539155083333333,SPI,The initial (idle) state of the CLK line does not match the settings.
Can you get a picture of the other side of the red RF board? I have the impression that the RF component is a LT8910 or similar. V761 is using a XN297. FYI depending on how they use the LT8910 we might not be able to emulate it...
Ok I don't know what the ref means but I'm pretty sure it's a LT8910. The bit rate is 62.5Kbps which is annoying since the NRF based emulation that I've written cannot be used directly... I'm thinking the CC2500 will be able to emulate it but that will have to be tested. I can try to look into it but without access to the original TX/RX, it's going to be difficult in this case... If anyone has a spare, it would be awesome to send it my way, I can return it when I'm done.
So I can unsolder the analyzer? Was my dump readable? Can you suggest the right clock settings for the SPI analyzer? I think of triggering at falling edge, because otherwise it has little sense. I'm new to this and much to learn.
BTW, the external antenna on this transmitter is a fake. The whole antenna wire was hanging inside the case, and no way to fit it inside the plastic antenna stick. Another chinese crap...
The dump is readable, well done and SPI decoder configured correctly. Don't unsolder anything yet. In the hope that I can emulate it, can you do more dumps :
- one dump where you move only one stick in one direction or a feature button. Make sure to name the files accordingly like Aileron_mid_left_mid_right_mid.
- one dump where you launch a bind if there is a specific bind procedure on the TX
There might be a problem - after assembling the TX after photos the radio now refuses to boot with the analyzer connected. When I detach the CLK wire, it boots ok. I do not know what has happened. No shortcuts, no other things changed - just unscrewed the board and then screwed it to the same place. Have no idea what to do.
The logic analyzer must be USB powered otherwise the SPI bus will be affected.
You are right, that way it is working ok. I have tested channels, but without arming, and this has side effect of maybe reversing channels, so to return to the normal I need to bring the model and test if everything is ok. Will continue tomorrow.
Channels direction are not really important for now. What's important is to identify the bytes of the payload and bind. On the V761 remote even the trims have features, make sure to capture those too if this is the same on this remote.
The CC2500 can do GFSK @62.484kbps using M=59 and E=11. From what I see, all LT8910 advanced options are off (FCC, whitening, encoding...). So it should be doable. But not having the TX (& RX) is going to be quite a challenge since a single mistake in the datasheet interpretation will prevent it to work with little to no way to know what's really going on...
The receiver was turned on, then the transmitter was turned on, there was long "beep", or 2 quick beeps. Startup with receiver on.zip THR up 100% - down to 0%. There was the beep on up, and (after a pause) the beep on down. Without the analyzer the second beep comes quicker. Arming- Thr Up-down.zip Move the stick 2 times. Recording was stopped before 10s, so may have garbage at the end, or be shorter. Ail mid-left-mid-right-mid-x2.zip Move the stick 2 times. Ele-Mid-Dn-Mid-Up-Mid-x2.zip Move the stick 2 times. rud-mid-left-mid-right-mid-x2.zip
The model was reacting for each move as it should.
Move the throttle form 0 to about 40% and then to 100%. Movement was not linear, as I had to hold the plane not to fly away ;-) THR 0-100.zip The Aux channel switch move 2 cycles. There is a beep on each position change. 5th-mid-back-mid-fwd-mid-x2.zip Move the stick 2 times, full 10s recording. Ail-Mid-Left-Mid-Right-Mid-x2.zip The same as above, but with the model switched off, for comparison if there is a difference. Ail-Mid-Left-Mid-Right-Mid-x2 armed model off.zip
This is the 2 cycle stick move, but without the model turned on, and without the arming cycle (THR UP/DN) Ail-Mid-Left-Mid-Right-Mid-x2a.zip This is the 2 cycle stick move, but without the model turned on, and without the arming cycle (THR UP/DN) rud-mid-left-mid-right-mid-x2a.zip This is the 2 cycle of the switch, but there were no beeps, as the TX was not armed I think. 5th-mid-back-mid-fwd-mid-x2a.zip
The files are much shorter at this stage. When un-armed, moving the stick to the extreme is used to reverse the channels, but it has to be hold a while there, so I am not sure if during the test this happened. The model was reacting normall after I connected it after the tests.
Great, let's see if I can make something out of this. If there is an option from someone to get the TX (and RX) shipped to me that would help greatly since as I've said I need to write a full emulator.