Serial ports

KenHorse · 12-18-2004, 07:17 PM

I am currently using /dev/ttyS1 in a standalone binary that uses only Xon/Xoff for handshaking. This means DTR, RTS, etc aren't being used. The thing is, this binary obviously "opens and "closes" the serial port as part of its operation.

I'm hoping to set RTS to one state for 1 second , then reset it back to its original state, then call this binary. I want to use RTS as a "reset" line for an embedded processor that my existing binary sends a file to the processor's flash memory. I would have to do this external of the binary obviously.

I have a few questions regarding this:

1) I am pretty sure I can use ioctl() for setting and resetting RTS. But would the act of closing the device force RTS to a different state than it was left when port is closed (I need RTS to be high, until I specifically tell it to go low)

2) Is there anyway to manipulate RTS via a shell script?

Thanks in advance for any answers!

cppkid · 12-27-2004, 12:59 AM

I don't think that closing the connection will force RTS to change its state, but when the ttyS1 goes free some other process can access it and modify, So try to keep the control. Why you want to close the handle??
Anyway you are right that you can use ioctl() for the purpose, here is how to do it. And i don't know about the shell script for the purpose.
Make the binary file and call it from your script

Just kidding

In this code m_hCom is the handle to ttyS1

Code:

//________________________Set_RTS__________________
bool Set_RTS(void)
{
int nRet;
int status;
status = 0;
nRet = ioctl(m_hCom, TIOCMGET,&status);
	if(nRet < 0) return FALSE;
status |= TIOCM_RTS;
nRet = ioctl(m_hCom, TIOCMSET, &status);
	if(nRet < 0) return FALSE;
return TRUE;
}


//________________________Clr_RTS__________________
bool Clr_RTS(void)
{
int nRet;
int status;
status = 0;
nRet = ioctl(m_hCom, TIOCMGET,&status);
	if(nRet < 0) return FALSE;
status &= ~TIOCM_RTS;
nRet = ioctl(m_hCom, TIOCMSET, &status);
	if(nRet < 0) return FALSE;
return TRUE;
}

KenHorse · 12-27-2004, 08:49 AM

Quote:

Originally posted by cppkid
[B]I don't think that closing the connection will force RTS to change its state, but when the ttyS1 goes free some other process can access it and modify, So try to keep the control. Why you want to close the handle??
Anyway you are right that you can use ioctl() for the purpose, here is how to do it. And i don't know about the shell script for the purpose.
Make the binary file and call it from your script

Just kidding

The existing binary obviously opens the port as part of its operation. I don't have the source for it so I can't incorporate your code into it (thanks for the code by the way!) so I have no choice about closing the port before reopening it.

Here are the steps I'm trying to do:

1) Open ttyS0
2) Set RTS high
3) Wait 1 second
4) Reset RTS low
5) Close ttyS0
6) Run my other binary

I'll use your code and write a script to do all the steps above. One way to know if RTS is changed on closing is to try it!