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Topic: How to use a 74HC4050N Level Shifter? (Read 4967 times) previous topic - next topic


May 01, 2015, 03:58 pm Last Edit: May 01, 2015, 04:39 pm by mcufan
Yes, and this is why I understand the two connections RX -> 1Y and 1A -> TX (HIGH-to-LOW level shifting) in the sketch - but not the two connections TX -> 2A and 2Y -> RX (because this would mean LOW-to-HIGH level shifting as well).
It means only that will send received signal from the BT board through 74HC4050 input pin and get the VCC or 0 voltage at output - to arduino's RX pin, nothing else. It does not do LOW-TO-HIGH conversion as cannot rise from VCC voltage to higer, in this case from 3.3V to 5V. That why it is called HIGH-TO-LOW level shifter.

That have nothing to do with input signals voltage of receiving around 3.3V and sending to 5V device RX input! Well, just look the datasheet and given ranges for input and output signals depending on VCC, as well as propagation delays. Arduino at 5V power supply will perfectly fine interpret 3.3V as HIGH.

Look at some LOW-TO-HIGH IC datasheet:

If you want real HIGH-to-LOW and LOW-TO-HIGH IC, search for one or use both of upper IC families.


3.3V does take Arduino pins HIGH.

The only pins that need leveling are the 5V outputs. They connect to the A pins and the lower 3.3V comes out of the Y pins.

1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

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