LORA: RF SX1278 Review

This weekend, I did a prototype project using LORA SX1278 for a 433MHz project. A friend of mine sent me two XL1278 module.

When I received the modules, I was so excited to test it. I have experience with TI CC1101/CC430 and NRF905 and I would like to do a comparison in terms of development time.

Upon reading the datasheet, everything is very straightforward. With the SX1278 datasheet's help, I was able to develop my C++ SX1278 driver and make it work with TI MSP430 FRAM microcontroller. Unlike, TI CC1101/CC430, I don't need any tool like SmartRF studio to get all the settings. I can just do a register computation for the frequency. Everything is straightforward with this LORA chip.

Since I don't have a spectrum analyzer, I used my $9 USB RTL-SDR (Software Defined Radio) to capture signals in the air. 

I used Spektrum (link) to see if there are any activities in the air if I transmit something. This Spektrum is pretty basic and it does it's job. I just hope that it would have a hold function like a normal spectrum analyzer (like holding a peak detection). But still, it is a very helpful tool. I don't need to buy a spectrum analyzer. :D

Spektrum Interface (not an actual picture from my experiment)

Continuing with my experiment, when there is no one transmitting, RSSI levels are at -137dBm. I tried transmitting something (I used Spreading Factor of 7 and I am transmitting 128 packets in one shot) and the receiver got a 128byte packet at -19dBm.  That is pretty impressive. I haven't done my Friis equation transmission equation analysis yet but looking at this data, I believe we can achieve very far range with this one.

This is a very good module. However, I may need to try some other antenna and I may need to design a quarter wave monopole antenna by hand before doing our range test.

-Jeff


(I don't own any of the picture, please see the link)
Image from: https://www.ebay.com/itm/433-LoRa-SX1278-Long-Range-RF-Wireless-Transceivr-Module-SX1276-5Km-For-Arduino-/322929644930
https://www.rtl-sdr.com/spektrum-new-rtl-sdr-spectrum-analyzer-software/