FX30s - RS232 serial port signals

Hi all,

Is there a way to poll the DTR or RTS signals on the RS232 serial port on the FX30S modem from an app?

Thanks in advanced.

Best regards,


Hi Eddie

I think something like the example in this link will work


Except that the FX30S functions as a DCE - most examples on the net will be for DTE the signal directions are reversed e.g. RTS is an input not an output

Also you probably need the port set like this

!MAPUART: 15,0

Which gives “/dev/ttyHS0”

Except of course I only considered the FX30S WP8548 – things will be I expect different for newer FX30S devices

I hope this helps


Sorry Eddie, but I don’t think this is possible.

When you configure UART1 for service 17, the HSL0 driver is used, which doesn’t support flow control. If you use 15 as John suggested, the HS0 driver configures those pins for use with the UART. So you won’t be able to access these pins via sysfs.

Maybe you can look to see if stty can do this, or if there’s an ioctl you can call.