Off-by-one errors in Tx timing

Dieter Spaar spaar at mirider.augusta.de
Sun Apr 25 21:32:38 UTC 2010


Hello Sylvain,

On Sun, 25 Apr 2010 15:16:48 +0000, 246tnt at gmail.com wrote:
> 
> * For RX it always worked for TS=0 because in l1s_rx_win_ctrl we put the  
> first command AT(DSP_SETUP_TIME - 100) ... which when you do the modulo  
> 5000 is somewhere around 4944. So when we start executing the TPU scenario  
> in the interrupt handler, that first AT command will force to wait almost  
> an entire frame and the rx window will be properly placed in the next frame.

To be true, I don't know where the "- 100" in the recent versions come
from. In earlier version the actual AT time was 54 (DSP_SETUP_TIME -
TSP_DELAY - 6). This is about 50 us. However we had the same situation
(actual processing happens in the next frame) because the time to
execute the code after the interrupt occured till the TPU was
enabled took a little bit more than those 50 us. Probably the
code has changed in recent versions so that it tooks less than
those 50 us and "- 100" is needed.

Best regards,
  Dieter
-- 
Dieter Spaar, Germany                           spaar at mirider.augusta.de




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