Tcl - Re: Using TK to read/write to serial port, allowing stdout display and TK GUI control

Author

Re: Using TK to read/write to serial port, allowing stdout display and TK GUI control

norbert

2006-06-25, 10:05 pm

Hi,

Thank you for the quick response and helpful advice. I am going to
re-write the code using fileevent properly (if at all?). In the
meantime, I was able to use the 'after' command to recursively call a
read procedure (to read from the serial port), similar to the following
code I found for another entry on this group (for creating a counter):

***

set Seconds 0
label .sec -textvariable Seconds
pack .sec

proc tick {} {
global Seconds
incr Seconds
after 1000 tick
}

tick

***

Using this approach, I am able to acheive what I want at the moment,
however I do want to change the code to read/write from/to the serial
port in a more conventional manner.

It looks like other postings may have closed their issues. Should I
flag this as a closed issue?

Again, thanks for all the help, I really appreciate it.
Norbert

Adrian Ho

2006-06-26, 4:21 am

On 2006-06-26, norbert <norbert@student.unsw.edu.au> wrote:
> [...] In the
> meantime, I was able to use the 'after' command to recursively call a
> read procedure (to read from the serial port), similar to the following
> code I found for another entry on this group (for creating a counter):
> [...]
> proc tick {} {
> global Seconds
> incr Seconds
> after 1000 tick
> }
>
> tick

To be pedantic, this isn't recursion, since each call to [tick] actually
terminates long before the next call is started by the event loop.
Think of it more as a user-level interrupt service routine that's tied to
timer ticks. I think the distinction is important because if it really
*were* recursion (say, due to a logic bug), you'd probably have a stack
overflow and much badness before long.

In any case, the above is a classic Tcl idiom viz. programming with
events, and is certainly worth keeping in mind.

- Adrian

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