GPS Module RX/TX needs 1,8V - LM317. LDO or Logic Level Shifter?

Other Hardware General Electronics
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Hey Folks,

I need your experience/help with 1,8V Modules and Arduinos / ESPs.

I've got a GPS Module which has the following specs:
VCC:3,3V
RX, TX: 1,8V

GPS Modul from Reyax: RYS8833: RYS8833_Lite｜REYAX TECHNOLOGY

image

I've read, that the LM317 needs a minimum from 2V between Input and output Voltage to work properly.

In general(!) terms, what voltage regulator do you recommend to use a Module with 1,8V on an ESP32?

Thanks for your help.

2

What is the brand and type of the GPS module and can you give a link to it ?
What is the voltage of your power supply ?
Which ESP32 module do you have ?

I read your post five times, but I still don't understand it. If the GPS itself runs at 1.8V, then you also need to convert the TX and RX signals. Some ESP32 modules have enough 3.3V output current to also power other things.

1 Like
3

Hey

GPS Modul from Reyax: RYS8833: https://reyax.com//products/RYS8833_Lite

image

VCC (3,3 V) from esp32 will work - but the logic from UART needs 1,8V and this is the point where I'm not really now how to do it.
I'm using an ESP32 Dev Module. But to understand the solution I want to keep it general.

ps.: this guy is using the LM317 for communication with the module. But I'm not sure if this will work: NodeMCU Based GNSS Tracker - The Newest and Most Versatile Option! - YouTube

4

The GPS itself runs at 3.3V, but the UART logic levels are 1.8V.

You would need to use a logic level converter and a 1.8V source for the level converter.

Heaps and heaps easier to use a 'normal' 3.3V logic GPS.

1 Like
5

Thx for the reply.
Any recommendations for a logic level converter 3,3V <-> 1,8V?

6

Did you read the pfd files of the module and the chip ? There is a photo that uses a level shifter for the RX and TX signals.

In the red circle are mosfets that are used for level shifting:
afbeelding

You need a level shifter for the RX and TX signals.

This is a "bi-directional" logic level converter. It will work for your project if the wires are very short. https://www.sparkfun.com/products/12009

Sparkfun has basic information about logic levels in this tutorial : https://learn.sparkfun.com/tutorials/logic-levels/all

It seems to use very little current. I saw "11.5 mA" somewhere. The 3.3V pin of the ESP32 should have no problem with that.

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7

Nope, never used one.

I stick to stuff that uses 3.3V logic levels.

8

Thanks for your reply.
Yes the Level shifter on your screenshot will work - but it`s not a elegant method for a project.

Thanks for the other links- i will get a "bi-directional" logic level converter!

Best regards

9

Maybe this needs a little more explanation:

The "bi-directional" level shifters with mosfets are used for the I2C bus. They will weaken the RX and TX signals 30 times :scream: But those modules are cheap and available. It will work if you don't use a cable.
You would be better with a normal level shifter (not bi-directional), but I don't know a simple module :cry:

When a 3.3V SD card is connected to a 5V Arduino board, then a chip is used to buffer and to do the level shifting. Manufacturers of boards use a voltage divider with two resistors to make the voltage level lower and a mosfet or transistor to make the voltage level higher.

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The FETs used on the Sparkfun and other "level shifters" may not do so good with 1.8V signals.
Knocking 5V down to 1.8V is, in this context, a simple matter; raising 1.8V to 5V, or 3V3, is another (op-amp / comparator).

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