Re: GNAT.Serial_Communications

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

On 2011-04-19, Simon Clubley <clubley@remove_me.eisner.decus.org-Earth.UFP> wrote:
>
> 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.
>

I didn't remember this bit correctly. (It's been several years since I
wrote this library.)

When I originally wrote the library, I incorrectly believed that RTS/CTS
logic 1 and Tx/Rx logic 1 were at the same voltage levels. Since the
library was been used on both sides of the link, this didn't matter.
I later discovered that the "asserted" voltage level for RTS/CTS was
inverted when compared to the Tx/Rx voltage levels.

I've just looked around for a online reference and I see Wikipedia has a
writeup about it:

	http://en.wikipedia.org/wiki/MAX232

Simon.

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