FullDuplexSerial with 8N1? *SOLVED*

Nick Mueller

Hi!

Don't tell me, that it's OK to transmit 2 stop-bits if only one is required. I know that. But this is a slight speed-penality (10%).
FDS does transmit 2 stop-bits. See scope shot. The deltaT (bottom of screen) of 0.053ms is quite 1 / 19200.

I tried to reduce that to one but failed.
It's more than just changing the 'mov txbits, #11' to 'mov txbits, #10'
Seems ... ah well ... I shut up.

It's not a speed problem with SPIN, the buffer is well filled and tx-speed was 19200 Baud. Nothing that would be "fast".
Its the same with 115200 Baud, but there I see jitter in the pause between characters. Not the topic.

Could someone point me to how to fix that in FDS, please?


Thanks,
Nick

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO

Post Edited (Nick Mueller) : 8/9/2009 10:57:59 AM GMT

Peter Jakacki

Your culprit is the infamous stop before start. I do it different but it is what it is. That shl 2 places only needs to be 1 place for the start bit.

                        or      txdata,#$100          'ready byte to transmit
                        shl     txdata,#2
                        or      txdata,#1
                        mov     txbits,#11
                        mov     txcnt,cnt

*Peter*

Nick Mueller

Thanks Peter!

I got it, code looks like this now:

  or txdata, #$100
  shl txdata, #1
  mov txbits, #10

the 'or txdata, #1' has to be removed.
Code checked with some text, $FF, $00, $AA, $55. All transmit fine, no bit lost ...


Nick
PS: Quite a cool gadged, such a protocol-analizer.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
Never use force, just go for a bigger hammer!

The DIY Digital-Readout for mills, lathes etc.:
YADRO