I was doing the schematics for the ESP module, and added a programming header without thinking about it too much. I mean, you gotta program the chip somehow, right?

Then I began to think more how annoying it would be to make a programming jig/board for this, and how 10 pin connector feels bit excessive anyways. What do I really need to get the ESP programmed? Well, basically the UART0 Rx/Tx pins.. and those are fixed to the level shifter and furthermore uses that weird connector, so that's not helpful... except.. maybe.. yes! I should in theory be able to use the USB-Serial module, that I was planning to make anyways, for also programming this ESP module. Sure, it goes through pair of level-shifters for no good reason, but it should work. As added bonus I could also program it with the 200LX itself also if I so desire.

Okay, the plan is not all roses; the thorn here being that both modules have the same female header connector for the serial. Meaning that I need to make a custom null-modem style cable for this specific purpose. But I think I can live with that, if it works. Failing to get it working for some reason, I think I can always fall back to either out-of-circuit programming (this jig looks kinda cute), or in-circuit pogo-pins (something like this). And OTA flashing would be neat too, so maybe I don't need to do wired programming all that many times.

The morale of this post is not as much the specific method of programming, but rather how I was initially kinda fixed on thinking that of course I need a separate programming system and then feeling clever that I got out of that idea and figured out a solution that is much more suitable here.

With the programming bit being dealt with, the schematics are almost ready. I would still like to put in an under-voltage protection to prevent brownouts, and maybe some other minor tweaks for the power supply. And then I need to double-check all the pin assignments etc and then comes the fun part; PCB layout.