I’m beating you on age by a decade, no bleating allowed there 
But I’ve been solidly involved (not as my full-time job, I’m really an electrical engineer) since the early 1970s. I’m not all that up-to-date with the details of Pi’s and modern networking, I defer to Brian and Paul on that.
I believe so. You need, if you don’t have it, the Arduino IDE on your computer (full instructions for getting it and installing the libraries etc you need are in ‘Learn’) and when you’ve done that, connect the computer and programmer with a USB extension cable (optional but advised) and the other end of the programmer to the emonTx - of course disconnecting the Pi and watch which way round you connect it. I don’t, can’t and won’t support platformio. That’s how I work all the time, and it suits me. If you desperately want to use platformio, somebody else will need to help you.
As I wrote earlier, I’d advise you to use the latest “CM” sketch in all your emonTx’s I’d also advise editing the sketch to disable the radio if you’re never going to use it. (And that’s even more important if you have RFM12B radios in some of the emonTx’s.) It’s a lot safer and very easy to disable it when you’re reprogramming it - and you’ll never need to worry about it again.
[Edit] It’s also going to be a good idea to give each its unique NodeID set in the sketch too.
Your first step will be to get the emonTx sending data to your computer via the programmer and the Arduino monitor screen.
When that’s OK, disconnect the programmer and connect your Pi Zero W. That’s running emonCMS? If you check (and change if necessary) the serial baud rate, and change the middle part of the node definition for the emonTx (whichever NodeID it’s using) to
names = MSG, Vrms, P1, P2, P3, P4, E1, E2, E3, E4, T1, T2, T3, pulse
datacodes = L,h,h,h,h,h,l,l,l,l,h,h,h,L
scales = 1,0.01,1,1,1,1,1,1,1,1,0.01,0.01,0.01,1
units = n,V,W,W,W,W,Wh,Wh,Wh,Wh,C,C,C,p
then the data from the emonTx should appear in the Pi Zero’s emonhub.log
I’d almost suggest that you do a very basic set-up (via a web browser over your LAN) of each of the PiZero’s, just so that you have confidence that the data is coming in.
I’ll stop there for now, because we’re getting into Brian’s networking territory, and there’s plenty there to be getting on with.
Would you like me to post a “non-radio” but otherwise standard “CM” sketch for you, or just a list of changes you need to disable the radio? (The first is easier for you, but you’ll learn more from the second.)
