Re: GNAT.Serial_Communications

[Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP>]

On 2011-04-19, tonyg <tonythegair@gmail.com> wrote:
>
> Just to let you all know ( I'm sure the world was waiting with baited
> breath!) that thanks to the help received, its now all working. I'll
> document what the problem was with some additional stuff to let future
> people know.
>
> It was the flow control setting and it can be fixed by opening another
> terminal window and using the command
>
> stty --file=/dev/ttyUSB0 -crtscts
>
> However - any ada program compiled with the gnat serial communications
> package if run again will reset the port to add flow control so this
> needs it will need to be done again. Which is unfortunate for me and

Interesting. I would not expect that; there may be something resetting
the port (maybe in the GNAT library or the version of the Linux kernel you
are using) without you realising it as I don't recall seeing that while
working with Linux serial ports (which, for the set of applications in
question, I do in C and not Ada).

> anyone with non flow control electronics. I expect this will occur
> everytime the port is opened. Out of interest do all you serial port
> tinkerers out there use flow control?

Yes. It's a hardware based RTS/CTS flow control setup and it's a integral
part of my microcontroller UART library (at least for the hardware UART;
I also created a Tx only software UART for my library and I don't support
flow control on that as it's just used for debugging).

This is for microcontroller to microcontroller communications however.

When I connect the devices to the Linux PC, I use the standard MAX232
setup and since it's been a number of months since I last did this, I
cannot remember if my library supports inverting the RTS/CTS lines
to allow the signals to pass through the MAX232 or if I just disable
the flow control on both sides as I am generally just debugging.

Given that I need to transmit 8 bit data on these ports, I have not
bothered creating a software flow control Xon/Xoff implementation.

Simon.

-- 
Simon Clubley, clubley@remove_me.eisner.decus.org-Earth.UFP
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