by Richard Russell, July 2007
Occasionally you may wish to send a break condition on a serial port output line. For example this may be needed to 'wake up' a remote device such as a modem. You can easily do that using the following code:
SYS "SetCommBreak", @hfile%(com1%) WAIT 50 SYS "ClearCommBreak", @hfile%(com1%)
Here com1% is the value returned from OPENUP when the serial port was opened. In this example the break condition is maintained for about 0.5 seconds (50 centiseconds).
For completeness here is a self-contained program which opens the port, sends the break, and then closes the port:
com1% = OPENUP("COM1:9600,n,8,1") IF com1% = 0 ERROR 100, "Couldn't open serial port COM1" SYS "SetCommBreak", @hfile%(com1%) WAIT 50 SYS "ClearCommBreak", @hfile%(com1%) CLOSE #com1%