How does this Arduino Micro Pro respond to 3.3V levels of digital input?

Using Arduino General Electronics
1

I am trying to combine this:
http://www.aliexpress.com/item/MPR121-Breakout-V12-Capacitive-Touch-Sensor-Controller-Module-I2C-W-12-keypad/1729953044.html?spm=2114.01010208.3.110.hqkL2K&ws_ab_test=searchweb201556_0,searchweb201602_2_10037_10017_10034_10021_507_10022_10032_10009_10020_10008_10018_10019,searchweb201603_9&btsid=1481552e-711b-4d8e-b080-18c65ce9e4db

and this:

http://www.aliexpress.com/item/Mini-Leonardo-Pro-Micro-ATmega32U4-5V-16MHz-Module-For-Arduino-Best-Quality/32284746884.html

The touch pad uses 3.3V for all it's needs and outputs 3.3V I2C signal.
Is this something that I can combine or would I need a signal level booster?

2

You mostly have to use a voltage divider to translate down any signals from Arduino to the touchpad, but not the reverse.

3

I2C is bidirectional, you need to use a proper bidirectional levelshifter. There's a cute little circuit that you can build with 2 resistors and an NPN mosfet (the small signal mosfet type thing, not a big power MOSFET) per line, google will find the schematic.

4

Yes, good idea. Since the OP is interested in the Aliexpress stuff, for 28 cents USD shipping included (is that crazy or what?):
http://www.aliexpress.com/item/1pcs-Logic-Level-Shifter-Bi-Directional-Four-way-two-way-logic-level-transformation-module/32619599294.html

There is also a 3.3V version of the Pro Micro. I notice the Pro Micros are crazy cheap on Aliexpress, too.

5

dmjlambert:
Yes, good idea. Since the OP is interested in the Aliexpress stuff, for 28 cents USD shipping included (is that crazy or what?):
http://www.aliexpress.com/item/1pcs-Logic-Level-Shifter-Bi-Directional-Four-way-two-way-logic-level-transformation-module/32619599294.html

There is also a 3.3V version of the Pro Micro. I notice the Pro Micros are crazy cheap on Aliexpress, too.

Would this specific level shifter work with my new keypad?

6

Boy! The level converter and Pro Micro are OK, but the touch pad sure is expensive from Aliexpress!
.

A Pro Mini is much cheaper of course if you do not need the USB functionality

and is available in a 3.3 V version.

dmjlambert:
There is also a 3.3V version of the Pro Micro. I notice the Pro Micros are crazy cheap on Aliexpress, too.

Now that is fascinating. I was not aware of a 3.3 V version of a Pro Micro though I see a thoroughly garbled description on this entry. 3.3 V Pro Mini for sure.

VT91:
Would this specific level shifter work with my new keypad?

That is what it is designed for.

7

dmjlambert:
I notice the Pro Micros are crazy cheap on Aliexpress, too.

Why is everything so much cheaper on the other side of the pond? Not that I'm jealous you understand. Nope. Not at all. Not. Not. Not...

Oooh, they deliver to that remote island called the UK too! Great, I'll add them to the Gearbest, Banggood and other suppliers. And that logic level shifter is just 20 pence, now that is crazy pricing, I'll have 10 please.

8

Nice find on the 28 cent level shifter. That's just insane. Looks like it's the same circuit I was referring to.