Hello,
I experimented with the RS-232 port of RUT955. We intend to use the handshake lines for some extra I/O (driving LEDs, reading switches) in our application.
https://wiki.teltonika.lt/view/RUT955_RS232/RS485#RS232_Connector_Pinout
I compiled a test program making standard ioctl calls (TIOCMGET, TIOCMSET) to opened ttyACM0 fd.
My results:
- The handshake line control bits are "DTE side": to change state of pin 6 (DSR) of the connector, bit TIOCM_DTR must be toggled, same for pin 8 (CTS) = bit TIOCM_RTS
- To read pin 7 (RTS) one must check bit TIOCM_CAR (=TIOCM_CD) instead of expected TIOCM_CTS.
- Pin 1 (DCD) does not change state when toggling any TIOCM_* bit, it is always at positive voltage.
Is this expected behavior?
I can live with points 1 and 2, but point 3 is problematic - is there any way to change DCD pin state?
With it (and the extra output at power connector) we have just right amount of I/O for our application, not requiring any extra hardware...