Right Logic Level Shifter for Right Product

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stann
Posts: 3
Joined: Mon Oct 02, 2017 1:43 am

Right Logic Level Shifter for Right Product

Post by stann » Mon Oct 02, 2017 2:00 am

Hi. I m using Arduino Mega 2560 R3 which has an AVR processor. My 5V Mega is interfacing with a HC-05 bluetooth umm card! I am using a basic voltage divider with 1k and 2k to reduce 5v signal to 3.3v signal from Tx of arduino to Rx of hc-05. And it works fine as far. As far as i am aware of level shifters that has umm transistors so i m thinking to use a level shifter to reduce ( or increase for future projects) the signal voltage in Proper Way. I saw some bi-directional level shifters. Some of them just have transistors like bss138 and some resistors. And they say its a bit sluggish.so they offer umm circuit type level shifters which have TXB0108 and 74HCT245 and so on.. no one wants to have a sluggish signals. So i thinkimg to use circuit for this level shifting. I sae in a site that AVR chips dont work good one of that 2 ( TXB0108 - 74HCT245 ). anyone has information about that compitability issue?

For example Teensy has ARM and they use 74HCT245 for level shifting on their board for teensy add-on. That means 74hct245 is compitable with ARM chip. But my mega has AVR.. which one is compitable for AVR.. because i saw one of them is not and i cant rememebee that website.

stann
Posts: 3
Joined: Mon Oct 02, 2017 1:43 am

Re: Right Logic Level Shifter for Right Product

Post by stann » Thu Oct 05, 2017 12:31 am

Realy?no one has any info about AVR processors and IC type level shifters compitability?

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exeng
Posts: 49
Joined: Thu Jan 05, 2017 1:37 pm

Re: Right Logic Level Shifter for Right Product

Post by exeng » Thu Oct 05, 2017 2:51 pm

Seems like this product from Sparkfun would work for you and it's bi-directional.
https://www.sparkfun.com/products/12009

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exeng
Posts: 49
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Re: Right Logic Level Shifter for Right Product

Post by exeng » Thu Oct 05, 2017 5:38 pm

So here is a link that compares the different level shifters [quote]http://happyinmotion.com/?p=1247/quote] and I see the a reference to the MOSFET signal being less that optimal for high speed stuff.

ARM vs. AVR? I would think that only the speed of the signal that you are trying to level shift would matter and how well a particular implementation of level shifting responds and reproduces that signal shifted.

stann
Posts: 3
Joined: Mon Oct 02, 2017 1:43 am

Re: Right Logic Level Shifter for Right Product

Post by stann » Fri Oct 06, 2017 5:39 am

Thx for ur interest but this kind of basic 1 transistor - 2 resistor styles are defined as sluggish! So i try to choose a Chip like TXB or 74htc

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