This morning, Arch Rock introduced a serious contender for the SP100 physical standard: an 802.15.4 radio with Internet Protocol (IP) native to the device. This means that ethernet, Industrial Ethernet, Modbus TCP, CANbus, Foundation fieldbus HSE, and a whole lot of other existing protocols can use this radio natively.
Control columnist and SP100 member, Dick Caro, said, "When I saw Jeff Mulligan's (from Arch Rock) presentation on his compressed IPv6 stack in Chicago, I was greatly impressed. It looks to be highly efficient, and about as brief as any equivalent protocol stack I have seen. Going to IP at the Network layer makes so much sense to me because of all of the existing protocols that could take advantage of it. For example, it would be so easy to port Foundation Fieldbus HSE to SP100 if the Network only handled IP. Since HSE uses UDP, I am reasonably sure that it doesn't care if the Network is IPv4 or IPv6. Also, Modbus/TCP could run untouched over an SP100 using IP at the Network layer.
"I made these arguments a few months ago, but there was no one except Jeff Mulligan to pick up on it. I hope we can settle on a Network layer that looks enough like IP to all the use of UDP and even TCP. By the way, only TCP is non-deterministic due to retries. UDP can be made to be highly deterministic such as in HSE."
Jose Gutierrez, former co-chair of the 802.15.4 committee, and now Director of Technology for Emerson Electric (the parent of Emerson Process Management), said in response to a comment from me that it didn't look like Arch Rock had any more latency than Dust or Raptor (the two competing physical layers), "Actually they do. SP100 is seeking 10ms latency, IP latency is in the order of hundreds of milliseconds. Remember that IP was never designed to be TDMA-based but CSMA. That means that there is no latency guarantees. On the other hand, more than 80% of the application do not require such a small latency, so their technology is viable."
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