RFC 9205 - Building Protocols with HTTP

OK, I have two use cases. CANBUS has no publicly-available HTTP interface. MODBUS has a "REST API" that's (sorry) really an anti-pattern of REST (not to mention, proprietary). I'll worry about CANBUS later. My aquarium hobby has me using a cheap seven-way sensor from China in my "dirted" tank; I only need six data points (soil moisture is always 100% lol), but it speaks MODBUS over two wires.



The "IIOT" (first I = Industrial) makes MODBUS unavoidable. Crying out for an API/Protocol (or whatnot) so I can monitor my fishtank from a browser or app, instead of a proprietary PLC with pushbuttons requiring physical access. Like a Hanna Instruments "GroLine" pH/EDC/TDS/temp monitor -- I'm just using the probe (nine total data points). Resurrected my last laptop for the DB9 RS-232 port, so I can use RS-422/485. USB requires a chipped dongle, and at this point, "the less stack the better". Hanna's probe uses an 8-pin DIN connector, the Chinese sensor has bare wires, but they're both 12VDC. Multimeter shows signal wires at 3.3VDC.



For those who don't remember or never knew, your UART chips gotta run at the same voltage. Old lappy does 3.3 or 5VDC on RS-232, 5V on USB. Took me some hemming and hawing about "how does this work" before I whipped out the multimeter and measured signal-wire voltage. Issue #1, poll the sensors, or treat their output as streams?



If anyone is interested in helping me flesh out a RESTful MODBUS HTTP API/Protocol off-list, the "side purpose" would be fleshing out RFC 9205, and we'll bring that back to the list. Apply it to an open CANBUS HTTP API/Protocol, lather-rinse-repeat fleshing out 9205 for IIOT.



-Eric