I’m not deliberately trying to confuse you, but today’s pointer is to a blog by “Tinkermax” (as opposed to the previous one by “Tinkerman”) and it covers a novel way of adding addition al ADC inputs to the ESP8266 using a low-cost analogue switch chip.
As you can see from Tinkermax’s photo, the chip itself is absolutely minute (compare the chip to the size of the SMD caps and resistor) and the most difficult part of this project is undoubtedly the soldering. The FSA3157 chip used only needs a single data line to switch between two inputs (while the FSA3357 can be used to multiplex three inputs, at the cost of an additional data line). Both chips also work on a fairly wide supply voltage range, so either 3v3 or 5v is fine.
Given the simplicity of the circuit and low cost of the device, this seems like a nice way to go if you need to add extra ADC channels and don’t mind sacrificing one, general-purpose I/O for the switching. The absence of any requirement for support circuitry for the chip and the single data-line switching may offset the difficulty of soldering. On the other hand, a couple of P-channel MOSFETs are probably more readily available in most people’s component drawers.
Anyway, it’s an interesting article and Tinkermax also has some nice information on reducing battery draw for the ESP, as well as some nice projects. Well worth visiting.