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UART communication between RPI Pico W and Arduino Nano

lovrinho

Apr 5, 2023
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I need to make a UART connection between these two board but since the Nano works at 5 V and the raspberry works at 3.3 V I need additional components.

My question is: is it enough to use a simple voltage divider with a couple of resistors and how reliable and safe is it?

I want to use the resistors because I don't have time to order new components and wait for them to arrive.

Thanks in advance :)
 

Bluejets

Oct 5, 2014
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Then there may be difference in comms speed/frequency.

Voltage divider might be ok but the devil is in the schematic drawing you failed to provide.
As far as that goes, why not use the level shifter modules, not as though they are "expensive".
 

kellys_eye

Jun 25, 2010
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The data path is bi-directional so you'll need level changers for both directions unless the Nano is happy discerning logic levels that 'only' rise to 3.3V (high) which, for most devices, is acceptable but, depending on the application (speed notwithstanding) may introduce errors.

To do the job properly you should use bi-directional devices BUT a series resistor with clamping diode (zener) is better as a simple resistive divider will affect the 3.3V to 5V direction too.
 

Harald Kapp

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Nov 17, 2011
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a simple resistive divider will affect the 3.3V to 5V direction too.
Naah, a UART uses separate Tx and Rx lines, so a resistive divider on the Rx line (Nano=Tx, Rpi=Rx) will not affect the Tx line (from Rpi to Nano). But a zener as additional protection won't hurt either.

For the other direction (Nano=Rx, Rpi=Tx) it is worth trying out a direct connection. The Nano may be happy with a 3.3 V logic High.
If this should not be the case, a simple level shifte rusing 2 resistors and a single Bjt should work, as UART signals are comparatively slow. Here's a link to an example.
 

lovrinho

Apr 5, 2023
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Hi, thank you all for your answers.
Since I haven't done any projects like this before I will explore a bit more, chack if Nano will accept 3.3V from rpi and try to come up with a schematic but I'm new so it will take time.

I will try to remember to let you know what I used in the end and what worked for me so others can learn from this :)

P.S. this link unreachable from my side unfortunately.
 
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