How to simulate incoming character in serial communication?

Stor_G · 08-30-2004, 09:14 AM

Hi all,
i once found a way to simulate an incoming character to a serial line using ioctl.
since then, however, my memory has betrayed me and i can't find the code in which i used it nor the website which described the process.
anyone can reference me to some appropriate docs or give an example of doing that?

Thanks.

cppkid · 08-31-2004, 12:20 AM

I have done a little work in serial communication, I am sorry i can't understand what do you mean by simulate a character. Plz tell me what you want to do, I will try if i can solve your problem.

Stor_G · 08-31-2004, 08:28 AM

suppose i want to read data from a serial communication which is connected to another computer.

Code:

read(FileDescriptor, &Buffer, BuffSize);

and now another process on the first computer wants to send data through the serial line but to itself, the process won't be able to use

Code:

write(FileDescriptor, Data, sizeof(Data));

because it will arrive to the other computer.
so there's a way to use ioctl with a certain option that is specific to termio architecture. i found yesterday something that might be it, but haven't tested it yet.
if you have any idea, your help would be appreciated.

Edit: misuse of words....

cppkid · 08-31-2004, 09:06 AM

May be i don't have enough knowledge of it but till where i got it, its not possible.
Look you have opend a FileDescripter to a serial port let's say ttyS0, and its connect to someother computer, Then how can the computer send data to itself by writing to that serial port which is connect to someother computer and why a process want to use the serial port to send data to itseld that is connected to someother computer.

Quote:

and now another computer want to send data through serial line but to itself

For me it doesn't make sense, I think i didn't have enough knowledge of it, Sorry Buddy.

Stor_G · 08-31-2004, 09:15 AM

i think this is supposed to help
http://man.netbsd.se/?find=tty+4+20
but i haven't had time to test if it works on my distro (RH 7.3)
obviously i'm looking for a portable way to simulate incoming data from the remote computer.

Stor_G · 09-01-2004, 02:03 AM

Didn't work

anyone has an idea on how to do this?

cppkid · 09-01-2004, 02:08 AM

Stor_G !!! Sorry for asking again and again but can you tell me why you want to use the same port to send data to some other computer and to send data to itself.
And when that prot is connected to some other computer HOW can you send data through this port to itself and why???
Whatever you will write on that port will be written to the TX pin of serial port and that TX is connected to RX of other computer, not the RX of itself then how can the data be recieved by the computer itself???

Stor_G · 09-01-2004, 02:22 AM

well, there's a program that communicates with a device using serial communication.
there's another process the monitors some information and according to that info has to simulate as if the device sent some certain signals through the serial line.
i was hoping that some kind of internal buffers loopback was possible using ioctl or another method. (that way you don't actually use the serial port itself but send the data directly into the input buffer)

but so far i have only found one that works with terminal windows.
i figured maybe i could use this to simulate serial comm which is implemented similarity. however, that didn't work and i got a bad file descriptor error...

any ideas?

Edit: where did that sentence come from?