What is correct logic level output voltage of ESP8266?

Other Hardware General Electronics
1

If the IO of the ESP8266EX is a 3.3 V logic level, then why every one use resistors to divide logic level output voltage when connecting Reyax RYLR998 module to it.

2

You seem to consult uneducated people only. Level shifters are required only for use of 3.3V modules with a 5V controller.

4

I moved your topic to a more appropriate forum category @mrnams.

In the future, please take the time to pick the forum category that best suits the subject of your question. There is an "About the _____ category" topic at the top of each category that explains its purpose.

Thanks in advance for your cooperation.

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5

The ESP8266 is using 3.3volt logic.
The RYLR998 seems to use the same 3.3volt logic.
No level converter needed.

You must make sure both units are powered when connected together,
otherwise you might need resistors between their pins to protect the I/O from phantom currents.
Leo..

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6

DrDiettrich is right, only people who do it wrong use resistors.

Instructables: At "Step 2" is a ESP8266 with resistors for the RXD input of the RYLR998: https://www.instructables.com/LoRa-IoT-Project-With-Arduino-ESP8266-Control-Rela/
In the comment below, it says that the NodeMCU has 5V output levels. That is wrong.

I think that was copied to other websites. They are all wrong :angry:

But I also see the 5V Arduino Uno board connected directly to the RYLR998 :grimacing: That is also wrong, that signal should be lowered with resistors.

RYLR998: https://reyax.com/products/RYLR998
Voltage of module (VDD): 1.8 ... 3.6V
Voltage of digital signals: 0 ... VDD
When it runs at 3.3V, then the ESP 3.3V signals are perfect. I would also add a protection resistors as Wawa wrote.

1 Like
7

Exactly, one made mistake and everyone carried it.

8

Can you please explain bit on protection resistors , how to connect them, share any link

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If you power the RYLR998 from the 3.3volt pin of the ESP8266, then no resistors are needed.
If you power the RYLR998 from a different 3.3volt supply, then use 3k3 resistor between I/O lines of the two devices.
That reduces fault current to a safe value in case one of the devices is unpowered.
Powering the RYLR998 from the ESP, no resistors, is the preferred way.
Leo..

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Many thanks for your time to clear my doubts.

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