ESP8266 Community Forum

- Sat Jul 09, 2016 5:09 am #50441 Hi folks,
I don't get it... There are lots of boards out there (like the Witty Board) that include a USB to Serial converter, like the CH340G, and additional level converters to shift TTL levels down to 3.3V to talk to the ESP. There are also lots of tutorials that talk about different methods to use your 5V USB to Serial converter with the ESP8266 using level shifting...

But why??

When I got my first ESP8266, the first question I asked myself was, do I really have to use 5V TTL levels in the first place? The answer, obviously to me (but to others??), was NO!

Almost ALL USB to TTL Converters support 3.3V operation, which means, you can just supply them with 3.3V and they will output 3.3V TTL levels.
The CH340G meantions this in the Datasheet:

CH340 supports 5V and 3.3V operation. When using 5V operation, supply 5V to VCC pin, and
decouple the internal 3.3V reference with a capacitor of 4.7-20nF from V3 pin to ground.
When using 3.3V operation, tie V3 pin to VCC pin and supply 3.3V power.

So, why do all people use 5V Vcc from USB and shift levels afterwards, instead of just converting 5V from USB down to 3.3V and use this as Vcc for everything else? No level conversion needed

Since I have a lot 5V TTL converters myself, I just made myself a USB to 3.3V converter:
http://www.thingiverse.com/thing:768406
Works out of the box with all 5V USB TTL converters I have...

So, if you design a new board, just drop that unnecessary level shifting Saves you money and lots of headache.

Hope that was helpful to you

Btw: Tell me when you actually see a board using 3.3V in the first place... I couldn't find one so far.

- Sat Jul 09, 2016 6:16 pm #50479 Nice.

- Tue Apr 17, 2018 9:44 am #75437

So, why do all people use 5V Vcc from USB and shift levels afterwards, instead of just converting 5V from USB down to 3.3V and use this as Vcc for everything else? No level conversion needed

But can't the ESP8266 take 5V rx/tx inputs? Or does it have to be level shifted for 5V operation? But I see your point about why working at 3V3 is easier...

- Tue Apr 17, 2018 12:24 pm #75442

But can't the ESP8266 take 5V rx/tx inputs?

No it can't. Why do you think it should? Just because it would be more convenient for you?

This question has been answered many times.

https://www.espressif.com/sites/default ... faq_en.pdf

Are the GPIO pins 5V compatible?
No, they are not. While many applications may get away by using a resistor voltage divider or series
resistor, we highly recommend using a proper logic level converter chip to interface with 5V logic.
Not doing so may lead to damage to the ESP8266 in the long run.