FreeBSD and controlling an alarm via relay

Boris Samorodov bsam at
Tue Jul 5 19:56:33 UTC 2011

On Tue, 5 Jul 2011 17:30:03 +0300 Achilleas Mantzios wrote:

> Most probably i'll go for something cheaper like this one 

> Could i use the ucom driver to talk to the USB device like a normal
> serial device, via /dev/cua*** ?

I use USB-to-7-RS232-ports devices via /dev/cuaU00-/dev/cuaU06.
Works like a charm. But you should find out what chip is used
for USB-to-RS232 bridge and (kld)load a driver.

> The above link says one needs to talk to the relay with:
> 8 Data, 1 Stop, No Parity,Baud rate : 9600

I've never changed those parameters.

> and the commands look like:
> FF 01 00 (HEX) 
> or 
> 255 1 0 (DEC)

> could i be able to specify those over ucom? 
> do you know any application, perl library, utility or just a guide for
> standard C serial port programming?

> i have used mgetty/vgetty in the past to control some modems.
> I do not know if there any fancier methods to access the serial port,
> but this is how i used to do it, back in 7.*
> /usr/local/bin/vm shell -l cuad1 -S
> where reads like:
> #!/usr/bin/perl
> #
> use Modem::Vgetty;

> my $v = new Modem::Vgetty;

> $v->device('DIALUP_LINE');
> $v->send("ATH1");
> sleep(5);
> $v->send("ATH0");

> if i could speak directly with e.g. "255 1 0" like
> $v->send("255 1 0");
> that would be awesome...
> i guess i will have to try it out.

I use python for scripting and it is as simple as write(data) and

HTH and WBR, bsam

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