The question maybe straigt forward.
I want to control a 3,3V LORA from Arduino and I am planning to use 4 channel level shifter.
So this calls for TX and RX pins to be shifted between 5V and 3.3V. I might use the other two for small OLED SPI display. And this way I will use all channals.
My question is about providing reference voltage on both side. So I have pins HV1-HV4 and HV on one side. So I preosume I can provide 5v to HV from Arduino 5V pin.
On the other side I have LV1-LV4 and LV. Would it be ok to provide 3,3V from arduino 3v3 pin to LV?
I cannot answer that because I do not know how things are interconnected or what modules you are using. Have you followed the crispy critter rules? Posting an annotated schematic showing exactly how you have wired it including all connections, power and ground. Also post links to hardware, LORA is a name to me. Do you mean LoRa or LoRaWAN? There are a lot of choices out there and for some reason I cannot see what you have and I do not want to burn the time trying to generate a lot of inaccurate answers. The good thing is you are asking before frying parts.
Crispy Critter Rules:
Rule #1. A Power Supply the Arduino is NOT!
Rule #2. Never Connect Anything Inductive to an Arduino!
Violating these rules tends to make crispy critters out of Arduinos.
Bidirectional level shifters only drag their outputs actively to low level. In your unidirectional case the high level requires a pullup resistor.
No
The 3.3V for the level shifter LV should come from the same power supply that is supplying power to the LORA
No it will not work.
You need a separate 3.3V supply for the LORA module
Specifically for the use of the level shifter and level shifting - Yes.
These level shifters are all pulled-up, depending, to 5V (HV) or 3V (LV).
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Can you explain why? I did a quick connection test with the simple led and the blink sketch using digital pin 3. If I connect that lin 3 to HV1 and connect + of second LED to LV1 and - to ground and connecting LV to 3v3 of Arduino I get both LED blinking. Second being a bit dimmer.
So that means that the signal was briged from 5V to 3V
The 3.3V output on the nano is limited to 50mA and I would not go over 40mA.
I'm sure your LORA module will need more than 40mA.
Ok . So in that case I need an advice. I wanted to do a mobile device . Powered from the powerbank DC5.V 2.1A. How do I need to connect it so it powers both Arduino Nano and Lora module.
I could do a separate power supply to Lora from 3,3v coin battery but how long would that battery last?
Not very long.
If you use the 5V power bank, you will need a 5V to 3.3V buck converter for the LORA module.
This module may work but first you need to find out how much current your LORA module needs.
Transmit Mode cuurent is 140mA
Power banks in many cases need to be busy or they shut off automatically for being idle (to save the battery for later).
There's a threshold, minimum current.
You probably need to see how yours fares in this regard.
Then the LM3671 buck converter will be OK.
Also take note of @runaway_pancake comments regarding the power bank
Thank you so much for your advice. I cannot find quick way of getting this particular part but I guess there are alternatives. E.g. I found a part I can get my hands on Monday
Input 4.5-28V**
Output 0.8-20V**
Output current up to 3A
I guess this one will do as well.
The ones with the adjustable output can be difficult to set and sometimes are not stable.
Also a 3A regulator may not be very efficient at only 140mA.
See if you can find one with a 3.3V fixed output and with a current rating of between 250ma and 1A
Can we revisit the level shifters? You're using bidirectional level shifters when none of your lines are bidirectional. The 3.3V TX outputs from the LORA module can be connected directly to the RX pin of the Nano. 3.3V will be read as high by the Nano. The 5V TX output of the Nano can be shifted down to 3.3V with a simple resistive divider (1K and 2.2K). Or you could have a pullup resistor to 3.3V on the LORA's RX pin, and a diode going back to the Nano's TX pin - so the Nano can only bring the line low, not high.
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I know that I can connect TX of Lora directly to Nano, and it works. But I thought it would be more correct to connect it via Level shifter to bring 5V signal to arduino RX. Will Arduino nano always recognise 3v signal as high? Also in the same project I was planning to use small OLED I2C display and planned to pass SCL and SDA pins through that level shifter as well