Thanks!
But how do You presume that anything else might be executed, when
sending chars.
You can't. That's the whole point of interrupts.
In your code one UART TX interrupt, is forcing another.
Usually the UART transmition is not time critical, and chars could
be sent only when processor is free. So for long time I am thinking
about
something like:
for(;;){
if (processor_free()){
usart_put_next_char(ch);
}
}
robert
There isn't any point in doing one character-per-main-loop execution
via interrupts. In your code above, just feed TxBuff and go do
something else. Check to ensure that the Tx buffer can handle the
outgoing character first, of course.
You will be "stuck" waiting for the outgoing character to clear
anyway, because e.g. at 9600 baud, one character takes 1.04ms to
send, which is a relative eternity. You may have nothing to do many,
many times in 1.04ms while waiting to be able to send the next
character.
processor_free() can be discerned pretty easily if you have some sort
of scheduler / RTOS. In our Salvo RTOS, you could put that call in
OSIdlingHook(). Then it would automatically send one character each
time the scheduler sees that there are no tasks eligible to execute
and the Tx buff can take the next char.
Even using Salvo RTOS, you would enter processor_free() at a much
higher rate that you can send 9600 baud characters ...
I'd use interrupts and send things out as fast as possible, and
control interrupts globally in case you can't tolerate being
interrupted.
It all boils down to your "and chars could be sent only when
processor is free" statement. You need to resolve what you mean by
that, and whether Tx ISRs can run in the foreground while your
processor is running in the background, doing mainloop code or tasks.
Since each Tx INT will only occur every 1.04ms, and will be very
fast, you should not have any problems sending these characters out.
Andrew Kalman wrote:
Does anyone has experience with uart transmit interrupt handling.
I would like to send long string of data, but not more, then one
character per main loop execution.
Is there interrupt based chars sending ever possible ?
I experienced, that during chars sending nothing is run, except
other interrupts.
robert
There was a long thread on USART TX ints a while back (2 months?)
in the MSP430 Yahoo group.
I posted my Tx USART code, which used a method of controlling TXIE
that solved the problem(s) of the original poster.
Here it is: http://groups.yahoo.com/group/msp430/message/13559
I use it so serve up web pages over TCP/IP on the MSP430 -- so the
strings are quite long, and there are lots of other things
happening while the ISRs are active and sending data. tested at
9600 baud with buffers ranging from 60 to 512 bytes.
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