Latest in Long range wireless small data communication between two arduino unos with no line of sight

Hello esteemed forum experts,

To explain the project in mind: We want two arduinos (e.g. Unos) to communicate small broadcast data packets over a long range wirelessly, hopefully reliably. This project is to enable a car to obtain broadcast message from a bicyclist in curvy road conditions to be aware and to prevent collision (assuming that both have the Arduino setup [uno+ long range wireless]) or similar IoT concept. Location is US west coast.

We are considering the following hardware:
-Arduino Uno, with battery packs and starter kit to help with different connections.

My request to the forum:
For the outdoor, somewhat long range wireless communication, I have seen many options (HC-12, Lora shield 915MHz – different variants/brands (like Dragino), Adafruit feather) mentioned but unable to choose one which will be easiest and most compatible.
In the real-life scenario, there may not be exact line of sight and the test condition assumes that both devices are mobile (car/bicycle). Given this, which LoRa shield do you recommend based on your experience.

I have looked at other topics a bit (the similar topic discussion seemed a few years old), and my requirements are a bit different (both moving units, no line of sight, direct device-to-device communication – there is no need for gateway at least in this initial version); also wanted the latest advancements out there, hence creating this new thread. Sorry if there is already existing thread. Please advise and/or point me to those.

As an extension, it would be nice to have GPS shield as well in addition to the LoRa to be able to provide some coordinates or direction (at the same time, not sure what is needed other than GPS shield to get it to work – any subscription is needed?).

If you have other interesting test cases or use cases to compare (currently we are thinking of varying distances, speed of vehicle) that come to your mind, please kindly share. Thank you much!

In terms of performance, distance etc, all the shields and modules are much the same, since they use the same Semtech LoRa devices.

The LoRa devices are 3.3V logic, so just make life easy do not use them 5V logic Arduinos such as the UNO.

Reception is very unlikely to be successful if timber or land masses intervene on the curves. The operative keywords are "clear line of sight".

It would be an excellent idea to get a pair of any of the standard modules and do extensive road tests before committing yourself to the project, or making a significant investment in the idea. The Feather M0 LoRa works very well, is ridiculously easy to use, and features quite a powerful Arduino-compatible MCU.

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For mobile applications especially on cars I think the antenna design and mounting locations will be a major factor in achieving good signal transmission. Go for a module with low loss RF connectors (SMA for example) and look at low loss cables and antennas to get your self started with the best signal possible. Make sure antennas are far from bike frames and good grounding practices are used.

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Thank you much for your quick response. Could you please expand on 5V compatibility? I was looking at the Arduino store and Uno, nano, micro, mega all have 5V operating voltage.

Spark has some 3.3V boards. Do you have any recommendations? Thanks again.

Arduino DUE, for a 3.3V Arduino with a lot of memory and IO pins.

Arduino ProMini 3.3V for a smaller board.

To connect a 3.3V device, which a lot are these days, to a 5V logic Arduino you need to use logic level conversion circuits or you can destroy the 3.3V devices. I much prefer to avoid the complication of logic level conversion stuff.

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