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Topic: How to level shift 5V logic to 3.3V logic for adafruit OLED display? (Read 2016 times) previous topic - next topic

Lustrousfiddle4

I need my Arduino uno to send sensor data to be displayed on my my adafruit OLED display through SPI.  What do I need to do convert the Arduino's 5V logic to 3.3V logic for the OLED display?  Adafruit sent a CH4050BE level shifter to go along with the display but after wiring it up the way adafruit described, I got no result.

I do not understand the way to wire an arduino to the level shifter to my display.
Is their a certain wiring pattern for wires going into the shifter and out?
What does the wiring look like for connecting arduino to the level shifter to the display?

Are their better and easier level shifters that would also do the job?

Would something like this do the trick? http://www.amazon.com/Adafruit-8-channel-Bi-directional-Converter-ADA395/dp/B00NAY2BBY


Adafruit display: https://www.adafruit.com/products/2719

Wired it up exaclty like in the adafruit tutorial:
https://learn.adafruit.com/system/assets/assets/000/028/428/medium800/adafruit_products_2720_redo_top_demo_ORIG.jpg?1446671749
 
Thanks!

Adafruit display: https://www.adafruit.com/products/2719
 
Thanks!

MarkT

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Lustrousfiddle4

I wired it up the same way the picture shows. Im very confused how the level shifter works and I don't understand why it should work the way the picture shows.
 
https://learn.adafruit.com/system/assets/assets/000/028/428/medium800/adafruit_products_2720_redo_top_demo_ORIG.jpg?1446671749

CrossRoads

The 4050 when powered from 3.3V takes in 5V signals and outputs 3.3V signals.

"They have a modified input protection structure that enables these parts to be used as logic level translators which convert high-level logic to a low-level logic while operating off the low-level logic supply. For example, 15-V input pulse levels can be down-converted to 0-V to 5-V logic levels. The modified input protection structure protects the input from negative electrostatic discharge. These parts also can be used as simple buffers or inverters without level translation."

So, power from 3.3V as you seem to have done, and you should see 3.3V levels out.
Write a simple sketch to just drive the output pins you are using High and low for a couple seconds, you should be able to follow the outputs as 3.3V level signals with a multimeter.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

MarkT

I wired it up the same way the picture shows. Im very confused how the level shifter works and I don't understand why it should work the way the picture shows.
 
https://learn.adafruit.com/system/assets/assets/000/028/428/medium800/adafruit_products_2720_redo_top_demo_ORIG.jpg?1446671749
Can see clearly what voltage you have powering the CD4050, I don't see decoupling on the
chip either.
[ I DO NOT respond to personal messages, I WILL delete them unread, use the forum please ]

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