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RE: serial ports on devboard_lx



Hi,

Thanks for your reply.

I tried out option 2 and it brings the performance to acceptable levels
(roughly 5ms greater than PC-to-PC results for 115200 baud).

A quick look at the code tells me that CONFIG_ETRAX_FAST_TIMER seems to
be a way of achieving better timer resolution not unlike "highres
timers" from MonteVista and KURT's UTIME approach
(www.ittc.ku.edu/kurt/). Is that understanding right? What is the
processing penalty in this case (in terms of CPU usage)?

Besides reducing interrupt processing, is there any other reason to make
the driver timer-driver instead of interrupt-driven?

What is the size of the serial FIFO buffers?

Thanks.

Regards,
Amit

On Wed, 2003-03-19 at 22:17, Mikael Starvik wrote:
> Hi,
> 
> With ETRAX it is a bit difficult to detect that a small
> number of characters has been received (and there won't
> be any more characters). We have three different 
> implementations that solves this in software (you can only
> enable one of them at any time):
> 
> 1. CONFIG_ETRAX_SERIAL_RX_TIMEOUT_TICKS. Set this to 0 for
> minimum latency
> 2. Enable CONFIG_ETRAX_SERIAL_FAST_TIMER (requires
> CONFIG_ETRAX_FAST_TIMER)
> 3. CONFIG_ETRAX_SERIAL_FLUSH_DMA_FAST gives minimum latency
> but impacts performance severely.
> 
> Can you try if any of these improves the numbers?
> 
> Another not yet implemented approach would be to make the
> driver interrupt driven.
> 
> /Mikael