Your project looks nice, but...I'm sorry, but I'd like to know what are the advantages of the CoAP over a well-known yet used as the Modbus-TCP (or UDP) is. Moreover, any Modbus flavor is totally free as licensing.
If you mean IoT leveraging HTTP and AJAX or XML, I agree that's nice, but that's a refinement of a worldwide-used industrial protocol. The only interesting feature is the access via URI other than a numerical code, but -you know- a string is somewhat "expensive" in term of resources. Modbus started in '79, where the strings were affordable just on PCs, not MCUs.
Could you clarify that?
That's pretty much the point. You may regard CoAP as a compressed form of HTTP, thus extending the REST architecture approach also to small embedded devices. In a way which allows to create fully generic gateways, with little or no "impedance mismatch" to the Web standards.
Again, where's the difference?
That's actually make sense to me. I've notice such a "big wall" between the abstract-web world and the real-life world. The majority of sensors telemetry/control users fall in the second class. However, I mean the pro-users, not the home's.
Totally agree, but -again- the actual context of IoT usage is pretty much home/small offices. I'd try to find a solution for the integration with existent systems, first.
Anyway, it's just another grain of sand in the world beaches!...
Wow, so many good questions...and I do not have a definite answer to all of them. Here is an attempt...
My understanding of protocols like MODBUS (or DNP3) is limited. I was trying to do a few things around SmartGrid, which is when I got to know about protocols like MODBUS and DNP3.
After reading them briefly, what I understood is that these protocols were designed, not by communications experts, but by H/W guys who also wanted their H/W to communicate...while I'm not that intelligent, but that's purely my understanding.
I come from a web background, and as stated by "Cuno" , CoAP is more of a web-world thing. Meaning, it suddenly has higher number of people who can easily understand this, bringing the entry barrier much lower.
Additionally, CoAP "is" designed to integrate with web, and that is where, if you read the specifications, there is reference to "CoAP to HTTP" and "HTTP to CoAP" proxy. Therefore, I agree with Cuno that CoAP makes getting on to the "Internet" easier.
While currently IoT is more of home usage as righly pointed out by Mario, that isn't really IoT, its more of machine-2-machine communication. I do have a few use cases (can't disclose now :-() where the usage is for commercial aspects and not just home usage.
Finally, I agree that strings are still costly on an MCU, but on small 8-bit MCUs like Atmega8 and the likes. More people (read hobbyists) have now moved on to more powerful controllers (e.g. FTDI, ST32, Atmega UC), and for them, string handling is easy ( i have experience on FTDI Vinculum and that handles complex structures nice).
My 10 cents to the discussion :-)
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