Pixhawk 2.1, graupner gr-16 (receiver) and mx-20 (emiter) connection

Hi all,

I’m trying to use the Pixhawk 2.1, gr-16 graupner receiver and mx-20 emiter to control my drone.
My problem is to setup this on QGroundControl
When I try to calibrate the radio this error happen :

Here my wiring :

and my transmitter :

The emitter and the receiver are binded together, gr-16 led’s is green.
Maybe my wiring is not good ? Maybe I don’t know how to use QGroundControl ? Do you have an idea ?
Thank you a lot

Up ! I change my wiring. I connect the 3 cables of telemetry and I put them on the channel 8 (that is normally en ppm-sum signal). On the MX-20 et change the mode to the SUMO16 mode.

It don’t work but I think it is a better configuration