Instructions here https://cosmostreamer.com/wiki/index.php?title=Cosmostreamer_settings#RC
Mode
Mode
UART device for SBus input. By default /dev/ttyAMA0 is used.
Depends on param "dtoverlay=miniuart-bt" in /boot/config.txt file:
If param "dtoverlay=miniuart-bt" is enabled: RC SBus may use hardware UART /dev/ttyAMA0, Bluetooth use software UART device /dev/ttyS0
If param "dtoverlay=miniuart-bt" is disabled: RC SBus may use software UART /dev/ttyS0, Bluetooth use hardware UART device /dev/ttyAMA0
On Raspberry Pi 4 possible to use additional UART. Need to add param into file /boot/config.txt
dtoverlay=uart2 for using GPIO1 as input
dtoverlay=uart3 for using GPIO5 as input
dtoverlay=uart4 for using GPIO9 as input
dtoverlay=uart5 for using GPIO13 as input