Level shifter question


#1

Hi,

I have several AK-3232 boards which I am using with a Pine64-LTS uart ports which operate at 3.3V.

One of them is connected to 3.3V Vcc and a Garmin 18x-LVS GPS receiver which works great! RS232 from the receiver to the uart TTL Rx/Tx pins and also the PPS signal to the CTS pin.

The other 3 AK-3232 boards are connected to Newhaven LCD displays:
https://www.newhavendisplay.com/nhd0220d3zflgbwv3-p-5742.html

Currently I am trying to find out from Newhaven if the LCD is RS232 or TTL as the manual and specs both say RS232 then have TTL listed in brackets (very confusing!).

If the voltage levels are TTL then what would be the correct level shifter board to go for to drive the displays?

I am looking at the TXS0108 V2. Would that be a good solution?

Virtually I would need to amplify the 3.3V signal to 5V if the LCD is in fact TTL. It actually most likely is the case as currently sending the command set to it doesn’t seem to function as expected so the display is probably struggling with the RS232 signal generated by the AK-3232.

What would you advise? Thanks :slight_smile:


#2

I made my own test on the LCD display. It does in fact need a serial TTL signal and not RS232.

The image below shows the result of the RS232 signal.

Looking here: https://www.artekit.eu/using-logic-level-converters/

it seems that I have selected the correct part. For Serial UART communication which is the correct choice: TXB or TXS?

Thanks.!

576-1024|281x500


#3

This image shows when the 3.3V TTL signal is applied directly from the Pine64. So I definitely need to convert 3.3V TTL to 5V TTL.


#4

Hello @kayasaman,

Sorry for the late answer.

Yes. It definitely requires a level converter. For an UART it is better a TXB.

Would a TXS version do the job? Yes. I’ve used it in the past to translate UART signals, but being an UART I would say that the TXB version is better.


#5

Hi Ivan,

thanks so much for the response.

Is the TXB available in the store?


#6

Hi @kayasaman,

Unfortunately, no, we don’t have it at the moment.

We are planing to release the TXB version later this year, but I can’t tell when.