I appreciate that there’s a lot to learn. Don’t worry, we’re used to it. I think you’re very close to having something you can work with.
Starting with the last post first, you’re getting the values passed through to emonHub, but it’s objecting to the decimal in the floating-point values. If you dig through our sketches, we only ever transmit integers, so what we do when it’s necessary to have a fractional value (for a temperature, say) is multiply by 10 or 100 at source and use "scales = " in emonHub to recover the true value.
If you look at the interfacers and the sketches that go with them, the code snippet I gave you is for the “3e” interfacer. This accepts “name:value” pairs - I think that means it doesn’t need/use a “nodes” definition in emonHub to give names to the incoming data.
The code for the plain direct-serial interfacer is space-separated values, which means emonCMS doesn’t have names, emonHub adds them according to the ‘nodes’ entry it has.
I think you’ll struggle to do much in real time, unless you slow the data rate down. You’re probably sending at 3 sets of data per second because you didn’t know better. EmonLib is like that because of history: the emonTx started out being battery-powered, so to get a reasonable life, it sampled for 200 ms, then went to sleep with just a timer running for 10 s, then woke up and did it again. So if you stay with emonLib, at the end of the main loop, you need to add 9 s or a bit more of delay.
emonCMS doesn’t use the SQL for the data, only for the metadata. The real data is in a home-brew database called PHPFINA or PHPTIMESERIES. These are documented (sorry, your learning curve just got a big step in it) in ‘Learn’ and you choose which one to use when setting up the Feed on the Inputs page in emonCMS. emonCMS will give you dashboards with the present data, and graphs and histograms for historic data.
No, I think that’s the sensible and obvious way ahead. If you want a shortcut, for the price of an SD card you can download a working RPi OS with emonHub & emonCMS ready to run - you’ll just need to connect to your Wi-Fi or Ethernet and edit emonhub.conf again. Then you can get to know emonHub & emonCMS and you’ve got a standard system which will make it a lot easier for us to help you. Then, when you know what you’re doing, if you really want to delve into the nitty-gritty, swap SD cards and carry on.