Alternatives to FrSky FrUSB-3/FUC-3

[andrewju]

Hi All,

This thread is more of a 'thinking out loud'. I'm not asking for specific help, but want to just share my findings.

Not so long ago FrSky released an updated firmware for XJT and X8R. Mine are quite old, so I definitely don't have the latest FW installed. Not that I need it much, but I'd still prefer to have the latest and greatest FW, just in case...

I read an upgrade manual, and it requires FrSky FrUSB-3/FUC-3 Upgrade Cable and a 'Smart Port Converter' (basically a diode to split Rx and Tx). I don't have FrUSB-3 cable to start with, so I searched the Net for a suitable replacement...

Looks like the FrUSB-3 is a USB to RS232 adapter with the main difference from other USB-TTL adapters being that the signals are inverted.

I found a guide explaining how an FTDI-based adapter can be programmed to work with inverted signals. One needs FT_PROG utility to change certain parameters in the EEPROM of FTDI chip, and then it should just work.

Has anyone tried to upgrade XJT or X8R with an FTDI-based adapter?
I believe it should be quite straight-forward, although for some reason this method does not seem to be wide spread...

[EDIT: I just checked this method, and it's pretty much straight-forward. Everything worked just fine!]


Another possible option would be to build a hardware inversion circuit. Something similar to the one we make in order to connect S.Port to a 9x. This way it may be possible to use other adapters (I have a CP2102 at hand), but latency could probably become a concern...

[MikeB]

Is that CP2102 just an adapter, or the development kit board?
I have the Dev kit and that has a row of links between the processor and the RS232 buffer. With that, you can use the signals from the links as TTL non-inverted, or the RS232 signals that are inverted.

Mike.

[andrewju]

I have just an adapter - like this one:



I also found an FTDI-based adapter. So it shouldn't be an issue to reconfigure it for inverted signals.




Just out of curiosity, would something like this work as an inversion circuit?

EDIT: The image is updated after Mike's comment below.

[MikeB]

Not quite. The diode is in the wrong place.The S.Port signal should connect directly to the 10K resistor, not through the diode.
The diode should be in the 'other' signal line.
The SPort signal is really bi-directional, the diode blocks the low voltage output of the Transmit data while the logic signal (TxD line of USB-TTL) is high.

Mike.

Edit: Image in previous post has been updated to show this change.

[andrewju]

Ooops! Of course...

I updated the picture in my previous post.

Should be better now.

[MikeB]

Looks OK now!

Mike.

[andrewju]

Ok, thanks a lot!

Maybe someday I will put it together, just to test...

[Kilrah]

Some small and cheap RS232<->TTL converters have started appearing on ebay:

http://www.ebay.com/itm/2PCS-Serial-Por ... 4865952eb4

[davx]

I have just an adapter - like this one:

Hi,

I've just done an X8R and Taranis internal XJT update with the same kind of adapter (CP2102) which I've paired with this converter (MAX232) to invert the signals :


Before that, I had tried with a PL2303 chip based adapter and it was not working, was getting "device time out" error...

Tchao

[Carbo]

Just to sort it out for me, this is only necessary, if you have no rs232 port nor an usb-rs232 adapter? Why would you want to convert the level from RS232 to TTL, when SPort Update needs RS232 level?

The update with a native RS232 port or an USB/RS232 adapter is rather simple, works on all SPort devices:

viewtopic.php?f=97&t=4003#p58236

[davx]

Yes, you're right but like I wrote in my previous message, my USB-RS232 adapter would not work so I had to find another solution

[andrewju]

Just to sort it out for me, this is only necessary, if you have no rs232 port nor an usb-rs232 adapter? Why would you want to convert the level from RS232 to TTL, when SPort Update needs RS232 level?

The update with a native RS232 port or an USB/RS232 adapter is rather simple, works on all SPort devices:

viewtopic.php?f=97&t=4003#p58236

Yes, you're right.
The thing is that many (most?) relatively modern PCs do not have RS232 ports anymore (especially laptops).
And many cheaper USB adapters are actually TTL-level, not real RS232.

So the post above may be useful to those of us who happen to be in this kind of situation and without a stock FrUSB-3...

BTW, converting levels with a Max232 is also a good (and very logical) way to do this...

[Carbo]

OK, got it. I did not realize, the converter is the max232 and can work in both directions.

[flybabo]

Not quite. The diode is in the wrong place.The S.Port signal should connect directly to the 10K resistor, not through the diode.
The diode should be in the 'other' signal line.
The SPort signal is really bi-directional, the diode blocks the low voltage output of the Transmit data while the logic signal (TxD line of USB-TTL) is high.

Mike.

Edit: Image in previous post has been updated to show this change.

Is the bidirectional S.PORT line internally pulled down?

[MikeB]

On the 'proper' hardware it is because the receive circuit is a transistor and 2 10K resistors pull the signal low.

Mike.

[rihcard]

hi guys,
can i use USBASP v2.0 alternative to frUSB-3? or CP210x? its for s.port upgrade. for FRUSB3

or can i buy this PL2303HX

or this FT232RL

or this FT232RL FTDI

richard.