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What is the fastest baud rate availible in FullDuplexSerial? — Parallax Forums

What is the fastest baud rate availible in FullDuplexSerial?

MicrocontrolledMicrocontrolled Posts: 2,461
edited 2010-07-23 01:51 in Propeller 1
What is the fastest baud rate you can set it for? I would like a max of 1M, but if it can go higher that would be nice.

Thanks,
Micro

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Comments

  • KyeKye Posts: 2,200
    edited 2010-07-22 14:24
    I honestly don't know how Full Duplex even runs at 1M. I've had no success at that setting on my platform. Then after looking at how it does timing I really don't know how it runs at 1M.

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  • Clock LoopClock Loop Posts: 2,069
    edited 2010-07-22 14:25
    I wasn't able to get faster than 300kbps prop to prop without the data being corrupt.
    Each prop was about 4 inches from eachother.
    I was required to use a 10k pull down resistors to quiet the noise on the tx/rx wires, to just get that.
    I was also using solid core wire.

    If I had a prop to prop PCB setup, using 10k pull down resistors and shorter wires, I would imagine the speed would increase.
  • MicrocontrolledMicrocontrolled Posts: 2,461
    edited 2010-07-22 15:40
    I'm doing Prop to PC communication

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  • JonnyMacJonnyMac Posts: 9,208
    edited 2010-07-22 15:45
    If you can spare a cog you could use separate TX and RX objects that would allow for greater speed -- and simple code.

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  • RaymanRayman Posts: 14,889
    edited 2010-07-22 16:03
    I remember in this thread:

    http://forums.parallax.com/showthread.php?p=835874

    That I got up to ~460000 using JDcogserial from OBEX...

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  • ke4pjwke4pjw Posts: 1,173
    edited 2010-07-22 16:03
    I was able to wring out 500kbps by disabling the TX via it's ping pong routine. I had to write my program in PASM and have it read directly from the circular FIFO. After looking at the timing of the operations, I think that's about as fast as it gets. That wasn't good enough for my project.

    I had plenty of IO lines available and started to investigate the FTDI UM245 breakout board. I am able to get much more speed out of it than the prop plug. I wrote the FullDuplexParallel Object for use with the FTDI 245 chip. I think that 3Mbps is doable with that combination. I have measured over 1Mbps throughput without any errors.

    PS: The Parallel FIFO is presented as a virtual com port on the PC side, so there is no reason to rewrite anything on that side.

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    Post Edited (ke4pjw) : 7/22/2010 4:11:09 PM GMT
  • Cluso99Cluso99 Posts: 18,069
    edited 2010-07-23 01:01
    The pingpong routines limit its speed. IIRC it was stated ~225,000 was the max. However Beau did some work for much faster comms ~8MBs

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  • localrogerlocalroger Posts: 3,452
    edited 2010-07-23 01:20
    If you have a pin to spare you can do much better with synchronous comms instead of async; instead of waiting for a fixed timeout you're basically waiting for WAITPEQ and then going on to the next bit. Has the advantage that if either link has to break off to do other work it pauses the comms instead of breaking them. I would consider custom comms for any prop-to-prop app, and FDS mainly for other devices that need serial comms.
  • jazzedjazzed Posts: 11,803
    edited 2010-07-23 01:42
    I've used 230400bps with 80MHz clock before no problem. Just stick with 115200 if you can for safety.

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  • Mike GMike G Posts: 2,702
    edited 2010-07-23 01:51
    I build a 1/2 duplex 1Mpbs serial driver using a one COG based on FullDuplexSerial. Should be able to do full duplex using two COGs.· I actually built the framework but stopped because while it was a neat thing it was not needed for my project.·
    ·
    My best FullDuplexSerial was 125K but that was PC to the Propeller Demo board.

    Post Edited (Mike G) : 7/23/2010 2:05:49 AM GMT
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