[EMAIL PROTECTED] wrote: > Hello, > > We are working on a new TDMA MAC protocol for wireless networks and I am > interested in possibly integrating this in to RTnet. We had been
You are welcome! > planning on using Atheros (madwifi) drivers, but I noticed that someone > has done initial work on Ralink. > Well, we once considered Atheros as well, specifically as 802.11a would have been interesting. But the binary part doesn't make it easy (carefully expressed), though it should be feasible technically: I contacted Sam Leffers once on this but got no reply. So I disassembled the HAL myself and found not RT-problematic IRQ mask manipulation (CLI/STI). But Ralink has a far more open design + a reasonable availability, so we finally picked this. > > > Does the Ralink driver work with the 802.11a chipset (rt2561), such as > the Sparklan WMIR-168AG? The code looks only b/g. > Nope, only b/g. I don't know how much the 2561 differs from the 2500, but it shouldn't be that complicated to integrate it. Daniel kept the original driver layers. > > I would be interested in hearing any comments on how well the Ralink > driver works. If anyone has looked at a possible port of the Atheros > (madwifi-ng) driver, I would appreciate any comments on the feasibility > of that. > The Ralink driver is surely experimental. It works, the link appears to be stable, and I'm not aware of relevant bugs at the moment. But Daniel did only elementary tests for his thesis (round-trip measurements and a RTmac/TDMA test). Long term tests are outstanding. > > Also, is there anything else besides the README.drvporting that would > help get me up to speed on what it takes to integrate a driver to RTnet? > Asking on this list. :) > > We currently use GPS PPS for timesync and have msec slots synchronized > pretty well, though we will be switching to a distributed on-the-air > protocol eventually. We also have a distributed time slot election > scheme for dynamic TDMA schedules over multi-hop networks. What we do > not have yet is a NIC driver synchronized to our slot boundaries, which > is what I am now starting to work on. > Sounds really interesting. Do you consider to integrate your protocol on top of RTmac? If something is missing in its interface to do this, let us know. A bit background on our plans with RT-WLAN: it's clear that deterministic transmission is practically infeasible over WLAN, you simply cannot control the media with all those bubbling devices around today. Therefore our aim is to provide best-effort short latency data delivery with as much control on error handling as possible (real-time data often prefer drop-on-error over repetition). At the same time, attaching a RT-managed WLAN adapter must not disturb other RT-applications an a node in an unpredictable way, even in noisy environments. The latter aspect still needs more research. Jan
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