Arduino GPS communication problem

Hi to all,

I have a project that include GPS module and Arduino uno.

I use SIM28 as a GPS module, the problem is Arduino can not read any information from GPS (GPS module itself is working.).

Communication between Arduino and SIM28 is hardware serial RX,TX. When i measure this signal with an oscilloscope

SIM28 TX pin signal is like below;( 3V– 0V square wave)

|500x363

When i applied this signal to Arduino RX pin square wave has changed to 4 V to 2.8 V.

I figured out that Arduino needs logic level converter which converts 3V to 5V so i used the circuit below:

After that, SIM28 TX signal has changed to 5V-0.6V square wave as expected.(see below)

|500x349

|500x300

However, when i applied this signal to arduino RX pin, signal changes to 5V-3V square wave as below, and arduino can not read that signal.

|500x350

How can I communicate GPS module (SIM28) and Arduino, OR How can i convert my signal to 5V-0V, which will make it meaningful signal for my Arduino.

Thanks in advance.

A 5V Arduino can usually read a 3.3V serial signal correctly. However, your scope traces don’t make much sense. Do you have the grounds connected together?

Please post a wiring diagram (hand drawn is fine, avoid Fritzing).

Thanks for the reply,

Circuit schematic is like below.

|500x396

Any help?

If you bought this from Grove, follow their directions for how to connect it.

Show me video. https://youtu.be/2dnB1kgVJT0