I am planning to build a sensor module for smartphone using Attiny 85 as its microcontroller.
The sensor module will have a USB type A and to connect to the smartphone, OTG is required.
Serial Communication (TX RX) will be used for them to communicate with each other.
My questions are:
TX of Attiny85 should be connected to D+ or D-?
TX RX of Attiny85 will have 5V for its logic signal voltage level. Do I need to use a voltage regulator to change them to 3.3V for the D+ and D-? Commonly, what logic signal voltage level is used for D+ and D-?
What is the max current can be drawn from smartphone's USB
Note: My smartphone model is Redmi Note 4. TX RX of Attiny will be done by using software serial following this guide https://www.instructables.com/id/ATtiny85-ATtiny84-Analog-Pins-Serial-Communication/