Re: Events on Serial port

Derek wrote, On 04.07.2008 11:07:
What do you mean by full speed, at the set baud rate?
I presume the latency in the actual write from the background is OS
dependant!, this may not be the issue but would have an impact on what
I'm doing.

By "full speed" I mean that in worst case bytes are transmitted as fast as the baud rate allows, one character after the other using the UART-FIFO (if no handshake).
And you don't have any control, because specially Windows is far from being a real-time OS with predictable timing.
Your OS may even decide not to send/receive characters even for seconds, if it thinks, that there is something more important to do.

If there are real timing restrictions on the receiver side, then you need handshake. Adding artificial delays after sending each character may help (I'm doing this), but there is no guaranty, neither for Linux nor for Windows.

I have quite strict timing, i need to detect and process RDS data
within 22mS worse case.
This is fine under Linux, Tcl is quite fast at doing the processing,
getting the data into the script is the slow part!

Generally that should be possible, but this depends on your baud rate and your serial driver settings.
E.g. in the device manager/com port/Port settings/advanced there is a slider for interrupt levels for your FIFO which radically changes your serial I/O latency. I prefer the Low(1) settings meaning that an interrupt is generated after reception of the first incoming character without any delay. The Higher(14) settings are useful for very fast serial transmissions (Modem Internet) to avoid overloading the OS with serial interrupts.

I'm not totally clear, where is your problem.
Do you suspect that sent characters are not received ?
Or do you have more trouble to detect and process incoming bytes ?
What is your baud rate and your complete [fconfigure] settings ?

Regards,
Rolf.
.

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