UART communication. Different Vcc

Hello everybody.

I am working on a new project, and because I want to incorporate in my car I have some power supplies constraints. Because it is illegal to incorporate a more than 12 V battery in my car, and because I do not want to care about this things, I have think in change my network power supplies.

So first of all I will explain what do I want to do. I have a set of sensors and actuators whose Vcc can be from 3.3 V to 5 V. Also I have a ICs multiplexer, so I can use the same arduino bus to connect many devices (PLEASE I DO NOT WANT TO USE I2C BECAUSE I NEED POWER ISOLATION AND IT IS SIMPLE TO USE UART COMMUNICATION PROTOCOL, PLEASE DO NOT RECOMMEND ME USE I2C). In Arduino UNO this communication is set in pins 2 y 3 (UART TTL).

The IC multiplexer, like ARDUINO UNO, must have 5 V of Vcc. What I want to do is use linear regulators to pass from 5 V to 3.3 V to supply power to my sensors, so they power consumption decrease.

The problem is that I do not know how electricaly, the communication UART ttl is done.I use UART ttl to communicate with sensors and I will like to know if I will have problems with the communication protocol if the Vcc are different. For example with the i2C bus (because they work as they work), I think this will not be possible.

I have to do these because I do not find specifications of the sensors to see how much Vcc deviation admits (for example until 5,1 V), and I do not want to damage them. Also I am looking for power isolators and most of them, even they are for example DC-DC 1:1 5V 1W, they have 5,4V output (I do not know if my sensors will bear with this).

Thanks you so much.

grupoExcellentia:
Hello everybody.

So first of all I will explain what do I want to do. I have a set of sensors and actuators whose Vcc can be from 3.3 V to 5 V. Also I have a ICs multiplexer, so I can use the same arduino bus to connect many devices (PLEASE I DO NOT WANT TO USE I2C BECAUSE I NEED POWER ISOLATION AND IT IS SIMPLE TO USE UART COMMUNICATION PROTOCOL, PLEASE DO NOT RECOMMEND ME USE I2C). In Arduino UNO this communication is set in pins 2 y 3 (UART TTL).

Thanks you so much.

check out TI TXB0104 level translators.

The UNO has a hardware Serial Device on pins 0 and 1. Pins 2 and 3 are just digital input/output. Pin 3 can be used for PWM.

chuck.