Date: Thu, 16 Mar 1995 11:35:12 -0500 (EST) From: Peter Dufault <dufault@hda.com> To: freebsd-hackers@freefall.cdrom.com Subject: Splicing in a new serial line protocol Message-ID: <199503161635.LAA04411@hda.com>
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Would anyone care to comment on where to splice in a new serial line protocol? I haven't looked at the code at all yet; I plan on looking later on today. I want to continuously receive serial data at 28.8 from four microcontrollers for up to three minutes. The frame protocol is this: * -> : Sender * <- : Receiver * * To reserve the line (not needed for grabbed link): * * ->ENQ : Bid for the line. * <-EOT : Grant the line * The equipment will always gets the line; * the host must turn the link around in case of a collision. * * To send a frame: * * ->STX : Here comes a frame * ->Sequence: The sequence number. * ->Stream : The stream code. Stream code > 128 "grab the link". * ->Count : The count. Up to 255 bytes. * ->b0...bn : The bytes * ->cs : The check sum * * If you did not grabbed the link: * * <-ACK/NAK : The ACK/NAK for the check sum. Not sent for grabbed link * * To request that the sender release ownership of the link: * * <- ETX : Ungrab the link, stop sending frames ASAP. Normally both ends bid for the link before sending data, but the link can be "grabbed" and then the data sent continuously (and it will be continuous - the microcontrollers are dedicated to collecting and feeding the data). I'm looking at bufferred boards for this (the Hayes ESP and the "Gtek PCSS-8FX"). Peter -- Peter Dufault Real Time Machine Control and Simulation HD Associates, Inc. Voice: 508 433 6936 dufault@hda.com Fax: 508 433 5267
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