How to solder - connect the sensor to an android phone?

Question

Android

How easy is it, where can I see an example of how to solder-Connect the sensor to an android phone?
For example, there is a humidity sensor, or a heart rate sensor from one phone on an android, and connect it to another phone.
as I understand it, you need to:
-solder (where?), a bus of some kind or parallel to something)
-find a driver (or write it yourself)
-how to adapt it to the current phone
- in the application code, refer to the sensor

Answer 1

I would use an Arduino (nano, if it's more compact - then mini) + bluetooth + a small battery and a hand strap (if the pulse sensor).
A pair of sensors is not a dusty job, a dozen or two lines of code on Arduino C can be written without particularly knowing the programming language.

Answer 2

If you ask such a question at all, then you should start with the arduino options that they offer here
. If it’s normal, then take the STM32 with USB OTG and hook the sensor to it, separate the board and order it on pcbway or in resonate with us.
In this option, everything will turn out to be extremely compact and reliable, the size of a coin (which you can’t do with arduino)