I just found the solution ...

I boot on an nfs server. I just transferred the files from the / boot folder to my SD card.

no problem with the RFLink module after reboot

Thank you again for your help !

For information, on RPI4 the way to the USB port is
/dev/serial/by-id/usb-Arduino__www.arduino ...

Thanks for help...
But the manipulations do not work


pi@raspberrypi:~ $ sudo modprobe ftdi_sio
modprobe: ERROR: ../libkmod/libkmod.c:586 kmod_search_moddep() could not open moddep file '/lib/modules/4.19.58-v7l+/modules.dep.bin'
modprobe: FATAL: Module ftdi_sio not found in directory /lib/modules ...

Thanks for your help :-)

This command return :
pi@raspberrypi:~ $ dmesg |tail
[ 9.841022] random: crng init done
[ 9.841036] random: 7 urandom warning(s) missed due to ratelimiting
[ 12.494954] uart-pl011 fe201000.serial: no DMA platform data
[ 12.927777] Adding 102396k swap on /var/swap. Priority ...

Hello everyone,

(Sorry... Google translate :D )

It's been 3 years since I was running with RFlink without any problem.
But since September 2, impossible to communicate with the arduino! (I changed the USB cable and even the arduino in doubt) on a Raspberry 4 with raspbian above
But nothing works ...