got a prototype working
I asked around for ideas. I was thinking about using IR or some analog RF. possibly abusing spi ports and generating 'some kind of rf' from that can can be picked up remotely. all I need is an on/off key pulse. if I had access to car keyfob chips (on both sides) that would be what I'd use.
well, espnow can do the job quickly enough and with a single chip. I was looking into lora or other radios but they all really need a local cpu of some kind. they cant just turn on and be 'seen' from the receive side (that I know of).
it has to be fast. cant afford to join an AP and get DHCP and so on.
espnow is just raw wifi frames (ethernet like) but does not do IP, does not need dhcp, etc etc. it just blasts and then exits.
video demo shows 2 wemos d1 esp8266 chips. the little box is a receiver (mode) and the raw chip in my hand is the sender; that would be on the probe body and you simply apply power to it via a momentary button and on power-up it shouts out an espnow packet.
you can see the delay in the 2 blue lights.
is that delay tolerable? I think so but curious what you guys think. if I take a reading and I'm watching where my probe is, if I get the reading inside 1/10 of a second or so (100ms) then I'm happy. I think this meets that but I need to logic scope this to see the delay number.
thinking even an esp01 chip will do this just fine. the 2.4ghz antenna on pcb is small enough. no battery drain on standby since its literally a power button.
video:
https://github.com/sercona/video_demos/raw/refs/heads/main/PXL_20240917_203505604~2.mp4