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Re: Serial communications


graham.labdon@cranems.co.uk writes:

> Hello Nick,
> Please forgive the direct approach but this issue has become a show
> stopper on my project.

I'm CC'ing this reply to the list, since it may be of use to others.
(Of course direct one-to-one consultancy is available, at a price.)


> As discussed in the forum I am unable to send more than ~128 bytes
> at time to my ecos program.  I am running this on the STM3210E dev
> kit and have tried testing it with minicom and an program of my own.
> I have tried reading the bytes as one block and reading the bytes
> individually.
> 
> within the ecos configuration tool I have set the serial buffer size
> to 512 and have changed the buffer size in stm32_serial.c
> 
> I have tried a variety of baud rates from 200 - 115200
> 
> Is there anything else I need to do?
> have you seen serial comms (not the ecos tests) working with data > 128 bytes?

The eCos test programs are a fairly good test of serial
functionality. That, after all, is what they were designed to do. Part
of these tests is to exchange varying sizes of data from a few bytes
to several K. These are all checked for integrity.

You may simply be suffering from the slowness of the external
SRAM. When you consider that you are fetching every instruction and
reading/writing all data over the same 16 bit external memory bus,
without any caches or prefetch buffers, then performance will not be
great. The STM32 is very much oriented to running code out of on-chip
flash.

You may need to switch to a ROM based application in order to get full
speed from the device. If you have a working RAM application,
switching to ROM startup should be easy. Of course a JTAG debugger
would make this very easy.

-- 
Nick Garnett                                       eCos Kernel Architect
eCosCentric Limited    http://www.eCosCentric.com       The eCos experts
Barnwell House, Barnwell Drive, Cambridge, UK.      Tel: +44 1223 245571
Registered in England and Wales:                         Reg No: 4422071


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