Experimental Physics and
Industrial Control System

"Owens, PH (Peter)" <[email protected]> · Wed, 15 Oct 2003 11:38:53 +0100

> -----Original Message-----
> From: LYNCH, Damien [mailto:[email protected]]
> Sent: 15 October 2003 01:11
> To: '[email protected]'
> Subject: Ascii SIO and alarms questions
> 
> 
> I am using Ascii SIO to handle the serial comms with a magnet 
> power supply. There are 8 commands that I send to the power 
> supply which expect a response.
> 
> Originally I had set up my database so that a different 
> command was being sent (via stringin records) every second. 
>
> It turns out that the power supply can't be tusted to reply 
> within one second. Occasionally a response from the power 
> supply was arriving
> late resulting in synchronisation being lost between the IOC 
> and the power supply. So what I need to do is be able to 
> recognise when I am in a late response situation.

Are you sure that it is the power supply that is taking so 
long to reply? I recently had a saw similar symptoms, but 
it turned out that the problem was with my low level serial
device driver buffering input.

In any case, there should be no need to send the commands 
one at a time. devAscii should queue the commands if another 
record is already using the line. (If it doesn't then that 
would be yet another reason to prefer streamDevice for
serial IO) 

The sychronisation does get lost if you set the timeout too 
short (then one record gives up the line, the next record sends 
it's command and parses the first record's reply). You should be 
able to put all your records on a 10 second scan without the need 
for any sequencing.

Also, you are not limited to using stringin records. devAscii 
can parse your response for and ai, bi etc record if that response
returning a value.

Pete.

Experimental Physics and Industrial Control System

Experimental Physics and
Industrial Control System