Lora 3.3V and Nano 5V when programming Nano

Hi Everyone.

I use a 3.3V regulator to supply power to the Lora Ra-01 and to the Nano on the 5Vpin.

Every thing works ok but when I program the Nano I unplug the Lora device to prevent the 5V on the data lines going to the Lora device.

Is there a work around to keep the Lora device connected to the Nano and program via USB using the pc 5V as power source?

Thanks in advance.

So your powering the 5V Nano from 3.3V instead ?

A logic level converter with one side connected to the 5V pin on the Nano ought to work, but I found logic level level convereters a bit marginal when running at SPI speeds.

The Solution is to use an Arduino that is designed for 3.3V use in the first place, Arduino Pro Mini for instance.

Thanks for the reply.

Yes 3.3V on the 5V Pin.

Looks like level converters is one option or cut the 5V USB wire in the program cable and use the external 3.3V as the power source .. A on my TO DO list.

As all (original) Nanos are 5 V with a 16 MHz clock, it may not be reliable at 3.3 V.

Indeed not ..................

Thanks for the info.

I tested a Nano with a 16x2 Lcd with the both devices on 3.3V and no display even adjusting VO does not work.

But using Vin with the build in 5V regulator the display is working.

So .. 3.3V is not the way to go since I am planning to use a Lcd on the receiving Lora device.


In this drawing the UNO is most likely working on 5V and the Lora is power from 3.3V will the 5V data lines not damage the Lora?

No image !!

Hope this works.


Where is "Preview"?

Yes and the 5V on the data lines can raise the VCC on the LoRa device to around 4.2V, absolute max is 3.9V.

3.3V is not the way to go since I am planning to use a Lcd on the receiving Lora device.

So use a 3.3V LCD.

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