w8sdz@WSMR-SIMTEL20.ARMY.MIL (Keith Petersen) (10/12/90)
The following article is of interest to anyone who has explored the idea of using a PC at very high baud rates, not just for Amateur Radio but for other applications as well. Keith [---forwarded message---] |Date: Wednesday, 10 October 1990 11:59-MDT |From: barry@dgbt.doc.ca (Barry McLarnon DGBT/DIP) |To: packet-radio@ucsd.edu, tcp-group@ucsd.edu |Re: Announcement: The Ottawa PI Board The WA4DSY 56 kbs modem has been available for about three years, and yet only a small number of them seem to be actually in use. One thing that has held it back is that it is not a "plug 'n play" solution - you have to build it up from a kit, and also provide external up- and down-converters between 28 MHz and the band(s) you want to use. This is really not very difficult, but there is another stumbling block: there has been no suitable hardware available for interfacing the modem to a PC/XT/AT. Most DSY users have hacked up a TNC-2 and installed a special version of KISS which allows the HDLC port to talk to the modem at 56 kbs, but the best the RS-232 port can do is 19.2 kbps (and some have even found it necessary to drop down to 9600 bps), so the capabilities of the modem are wasted. The DRSI card has also been used with the modem, in which case you can actually run at the full 56 kbs, but only by disabling interrupts and using programmed I/O to handle the 56 kbs packets. This means you can't service any other ports at the same time, which is not too useful for most situations. Now there's a better solution available. The members of the Packet Working Group of the Ottawa Amateur Radio Club have been enthusiastic proponents of the DSY modem since we first put some on the air back in 1988. In January of this year, we installed the first 56 kbs full-duplex repeater. As part of our group's ongoing commitment to promote the use of this modem in packet networking, we have developed an I/O board which overcomes the bottleneck mentioned above. Dubbed the PI board, it uses the standard ISA bus interface and DMA to provide full 56 kbs throughput, while still allowing other low- and medium-speed async ports to function without dropping characters. Used with NOS, this board has achieved FTP transfer rates of up to 5600 bytes/s over a 56 kbs half-duplex RF link. The board also includes a non-DMA low-speed port. A working prototype was demonstrated at the recent Computer Networking Conference in London. Lest I anger the net-gods, I hasten to add that the OARC is a non-profit organization, and that any proceeds from the sale of boards will be applied to improving the Amateur packet network. Nevertheless, this is all the sales pitch I plan to do via the Internet mailing lists. If you would like further details on the PI board and how to get it, please send *mail* to me: barry@dgbt.doc.ca Barry VE3JF