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Resolved Resolved by Dunning-Kruger!

Uart Port Voltage

Looking at the EZB spec sheet the UART TTL Voltage Level (input/output) is listed at 3.3 volts.

I am going to connect that port to a device that uses 5V TTL for communicating via serial.

I believe I would have to use a bidirectional logic level converter.

Am I correct?



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I am going say no or maybe. UART ports 1 and 2 are on pins 5,6 and pins 18,19 respectively and digital logic pins have a 5v input tolerance.... However, output on these pins is only 3.3v....

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Richard is correct.

Have a read of the datasheet which explains the voltages.

User-inserted image

All VCC pins of the analogue port, I2C port and UART0 are 3.3v, all signal pins are 5v tolerant. If your sensor requires +5v you will need to provide this from an external source or borrow a VCC from a digital port and regulate it down to +5v.


Most 5V Logic Parts work fine with a 3.3V Signal input. It is the 3.3V Logic parts that may not tolerate 5V Signal input. A simple resistor divider can fix the problem in some cases. A 1.5K ohm resistor in series with a 2.2K ohm resistor is a quick fix. The signal output of the 5V device goes to the open end of the 1.5K ohm resistor. The open end of the 2.2K ohm resistor goes to ground. The Signal input of the 3.3V device taps off of the joint of the 1.5K ohm and 2.2K ohm resistors.

This should work on digital or analog inputs. I have used it to attach a 5V output of an arduino to the 3.3V only input of a serial device with no problem. It also works well for 5V output Analog sensors to 3.3V input Analog inputs.


The EZ-B I/O input is 5 volt tolerant - so it will work with any 5 volt device without any additional components.

The output is 3.3v - but that's okay because anything above 0.5 or 0.8 (on most devices) is considered HIGH.

In short, the EZ-B will work fine with any 5 volt tolerate ttl serial devices without additional hardware.


Are you saying that we don't need an adapter for the digital or analog ports even though the bus is +12v for some of us?

I don't understand.


@Mel... DJ is talking about the signal pin of the ezb (white pin), not the power (Red) pin.....


The I/O signal wire is 5 volt tolerant on all ports, including adc.

The power wires are "what ever voltage you give to it"



So is my understanding correct that the UART 0 port tx and rx pins are 5 volt tolerant or are you only referring to the digital/adc signal pins?



Keep in mind that D.J. is talking ONLY about the Signal pins.