Hi Joao,
I hope you're having a good weekend, and thank you for responding so quickly. I've spent the morning checking and double checking everything again hoping to find the problem so as not to take up too much of your time, but still no further on.
To answer your questions, I assume the Arduino is outputting PPM ok as the led changes from a slow flash to a fast flash when I click on the Send SBUS button and the led on the FTDI flashes very fast.
The Arduino is connected to the Tx trainer port. The 3.5mm jack plug is wired with pin10 of the Arduino connected to the tip of the plug and the gnd connection of the Arduino connected to the gnd connection of the jack plug. The middle connection on the jack plug is not connected to anything. Is this correct? I copied the connections from the picture here
download/file.php?id=9363&mode=view When I go to the Trainer Menu the numbers at the bottom of the screen do not change, which from what you have said, I presume this is fundamentally the issue.
The connections from the Arduino to the FTDI are as follows :
Arduino FTDI
gnd------gnd
vcc-------vcc
rx--------tx
tx--------rx
dtr-------dtr
cts
The Trainer Menu is
RUD := 80% ch1 Switch RUD
ELE := 80% ch2 Switch RUD
THR := 80% ch3 Switch RUD
AIL := 80% ch4 Switch RUD
Thanks again for your help, I don't know what else to try...
Kind regards, Dougal