Maximizing baycom_par throughput

From: James Cutler (terhi.victor@logonet.com)
Date: Wed Mar 19 2003 - 20:31:58 EET

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    Hello,

    I'm trying to maximize output from a 9600 baud picpar modem, the
    Tigertronics BP-96A. I'm currently only able to send at a rate of 3600bps
    before the receiver detects missing packets.

    I'm using code that calculates throughput in an open loop fashion and
    throttles back the sending of packets when a limit is reached. See the
    attached code.

    When I set the modem in "full" duplex mode with sethdlc, I get the best
    throughput. However it seems I am paying the txdelay penalty on each
    packet, rather than on just the first one (since I'm sending a stream of
    continous packets down). So each packet is delayed by txdelay. I have to
    wait for each packet is sent in its entirety before I send the next one.
    Sending packets more quickly results in them being dropped and not
    transmitted.

    When I set the modem to "half" duplex mode with sethdlc, the throughput is
    worse. Packets are sent irradically and if I send them too quickly they
    are dropped as well. I've increased the buffer lengths in hdlcdrv.c which
    helps prevent the dropped packets but still they are sent irradically.

    I can't seem to get a continous multiple packet transmission from the
    picpar/baycom_par modem.

    Anyone have any ideas?

    Cheers,

    --James



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