easyIPC HL Part 1

easyIPC will be using SmartSPI and CAN-X for transport. I will discuss other transport protocols later. A transport protocol in this context is responsible for transportation of messages in a network from A to B and will cover layer 1 to 5 in the OSI layer.

I will introduce several transport protocols later. We need one for Ethernet and RS485. The RS485 one interest me. I have done Modbus and classic Master/Slave protocols on RS485 in the past, but I want to investigate the option to implement a multi-master Network on RS485. It is actually already been done in protocols like Profibus. The concept is that one device send and once that stop sending the second device will start sending within a few bits timing. The later is a challenge since MCU’s with standard UART’s might not be able to respond in time. If one device do not send the 3rd will start after a delay etc. The main limitation on RS485 is the latency implemented with Master/Slave sequences, so a timed protocol where each device can be active is very interesting. If this can be made to work with standard UART’s it will significantly improve the usability of RS485 networks.

An Ethernet protocol is less of a challenge. I have a design on a XML based protocol I am considering. This was one of the reasons I wrote my own XML parsers back in the days because I needed fast XML encoding/decoding. The drawback with a XML based protocol is bandwidth as it will use 50+% more, but encoding/decoding is actually faster than on a binary protocol. Also to limit the bandwidth usage we can do a few tricks. On Ethernet we can also use more classic protocols like http and web services. But, lets leave that and focus on the higher layer of easyIPC for now.

Leave a Reply