Nextion Intelligent touchscreen to Teensy 3.6

E

Elf

Well-known member
Is this wiring diagram correct to connect a 5V Nextion Intelligent touchscreen to a Teensy 3.6 through an SN74HCT125N level shifter?
Nextion_I_to_Teensy.JPG

Tx from Teensy is connected to input 1a on the SN74HCT125N and Tx from Nextion is connected to input 2a. Inputs 3 and 4 are not used.

Link to SN74HCT125N datasheet
 
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I had a Nextion working with Teensy 4.1 without a level shifter.
Used a seperate 5v supply but shared the grnd
 
Nothing I had read in all the info I reseached about the Nexiton mentioned the need or use of a level shifter.

I'm going to check it out
 
Nextion Intelligent series output voltages are 5V max and 3V min while the Enhanced series are 3V min and 3.2V Typical (Max is not specified).

Here's a quote from an Itead support email:
Code: 
Your question: What is the voltage on the Rx and Tx lines. Is it compatible with 3.3v MCUs?

Answer: Hi, friend, please add a 1K resistor series connection on Tx.

I don't want to add a resistor as my board can use either the Intelligent series or the Enhanced series displays.
 
I was feeding two analog inputs from PH probes into the T4. The probes were working on 5v.

I errantly hooked it all together without preventive measures.

The teensy docs stated 3.3v was input limit but I often read 5v on those analog ports without ill-occurance. (For months.)
I also had two Temperature probes on 5v rail going to digital inputs but they could not be read without current limiting resisters.
I had Tx and Rx from the enhanced Nextion connected without provisions.
(Used it for months like that)
The teensy is still going, but I now send the data out over wifi to my computer and do not have the Nextion hooked up any longer.

But I had no problems with the Nextion.

It seemed their biggest concern was the Nextion not receiving enough voltage/current, stated that could lead to damage.

I am still new to Arduino and should not be handing out advice.
 
I have these for use with my Nextion.
It's a nice small package intended for use with rs232.
They can be purchased on a breakout board from many places such as here and here.
By the way I see that Nextion have introduced an Intelligent version in 4.3" and it's cheaper than the Enhanced version. I have one flying it's way to me at the moment.
 
I have purchased about 20 different Nextion displays. I have had no problem providing Tx Rx directly from Teensy pins.
They are powered by 5 volts yet their logic is 3.3v
 
When I measure the voltage on the wire between the Teensy Rx pin and the Nextion Tx pin, I get 4.88V. Power reads 5.00V. Perhaps the Teensy is more tolerant than expected.

Here is the relevant section of the Nextion datasheet:
NextionOutputVoltage.jpg
 
RichardFerraro said:
I have purchased about 20 different Nextion displays. I have had no problem providing Tx Rx directly from Teensy pins.
They are powered by 5 volts yet their logic is 3.3v
Click to expand...

Different models of Nextions put out different voltages on their TTL serial output. I have tabulated the data below.
Intelligent Series ..... 5V
Enhanced Series ..... 3.2V
Discovery Series ..... 3.2V
Basic Series ........... 3.2V

So if you are NOT using the expensive Intelligent Series you should be fine.
Oops...I see you are using the Intelligent Series.
I have the same problem on a project I am working on, Teensy 4.1 and 10" Intelligent Nextion.
I will be using one of these as mentioned above:-

ADuM1200/ADuM1201 isolators provide two independent
isolation channels in a variety of channel configurations and
data rates (see the Ordering Guide). Both devices operate with
the supply voltage on either side ranging from 2.7 V to 5.5 V,
providing compatibility with lower voltage systems as well as
enabling a voltage translation functionality across the isolation
barrier.
 
It's really an excellent monitor
Click to expand...
So is the Nextion as an HMI with the benefit that the Human - Machine - Interface transactions can be offloaded to the Nextion display making the overall project much simpler.
It's called distributed logic.
 
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