Date: Wed May 15 2002 - 15:49:20 EDT

  • Next message: Chopin Cusachs: "[PARPORT] Tecmar DittoMax Parallel Port Tape"

    On 16 May, David Forbes wrote:
    > Hello,
    > I'm a new poster to this list. I'm a hardware engineer working on a data
    > collections system for a radiotelescope which is designed to read data
    > from a linear CCD into an industrial PC running RTLinux. The CCD
    > interface is all done in a Xilinx FPGA chip connected to an ECP port.
    > The data rate needed is about 150 kbytes/sec.

    I obtained regular performance of about 200 KB/sec without DMA. The key
    requirement is to get full use of FIFO reads. I then found that FIFO
    with no interrupts (they actually made things worse) and no DMA
    delivered 200 KB/sec in a similar situation. I was reading a CCD over
    the parallel port using ECP mode. The CCD chip wanted some fixed length
    commands (all 4 bytes) and responded with data (ranging from 4 byte to
    100K byte responses).

    I've lost track of versions because this was almost two years ago. The
    bulk of the code was done using ppdev device so that the chip controls
    could run user mode instead of device driver. In testing for production
    use this driver passed the 100K cycle performance test with sustained
    200KB/sec. 100K cycles for this device means 10,000,000,000 bytes
    transferred. It took a while.

    R Horn

    -- To unsubscribe, send mail to: --
    -- with the single word "unsubscribe" in the body of the message. --

    This archive was generated by hypermail 2b29 : Wed May 15 2002 - 15:56:51 EDT