FIFOed Avalon Uart

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originally posted by billooj@Sep 27 2006, 06:24 PM

i'm using the fifoed avalon uart with hw cts rts control flow to send data to a bluetooth tranceiver at 921kbps.

the bluetooth tranceiver send the data to a pc through a virtual com port configured at 921 kbps too.

my problem is that from time to time one byte send by software seems to be sent twice by hardware !!!

i send 1mbyte through the fifoed uart in high speed so flow control is often used by the bluetooth tranceiver, according to bluetooth datarate..

it seems that when fifo goes full or goes empty and then goes to in between state, the last or first byte is send twice.

i can see that in the file received : it's almost perfect, but sometines there is a duplicated byte. i can see that all over the file in no coherant manner..

fifo lenght : 1024

circular buffer lenght : 4096

does someone could try to explain what happens ??

thanxxx

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With the same buffers lenght, I reduce Uart datarate to avoid hardware control flow : the problem disappear ! So, it seems that when the Fifo never goes full : no byte is sent twice.

When I put buffers length as follow :

FIFO lenght : 1024

Circular buffer lenght : 512

It seems that byte duplication occurs more often.. maybe it could help to understand what happens ?

Ju.