The SparkFun SAMD21 Pro RF is the fated meeting of a SAMD21 and a long-range RFM95W LoRa®-enabled radio. The outcome is a compact, blazing fast microcontroller with excellent point to point data transmission in the 915MHz ISM radio band with LoRa capabilities. In this tutorial we’ll break down the capabilities of the development board, give you a brief introduction to LoRa and get you familiarized with the two Arduino libraries that will get you started with the radio and LoRaWan. If you’re familiar with LoRaWan then skip ahead to the Hardware Overview, otherwise let’s get started with a brief introduction to LoRaWAN.
Brief Introduction to LoRaWAN
LoRaWAN stands for Long Range Wide Area Network and describes the technology that allows for devices to send and upload data to the Internet using radio transmission. The technology is a frequency modulation scheme similar in theory but dissimilar to AM or FM which stand for Amplitude Modulation and Frequency Modulation respectively. You remember sine waves right? Amplitude modulation changes the height or amplitude of a wave when adding audio (or data) to it and frequency modulation would change, well, the frequency of a wave when adding audio (or data to it). The modulation scheme for LoRaWAN is more complex to explain but maintains this same theory of changing sine waves when they carry data; you can read more about it in detail below:
This scheme allows for data to be transmitted to the LoRa Network over a specific radio band known as the the Industrial, Scientific, and Medical Band (or ISM band for short). The frequencies of this specific radio band varies from country to country but as an example, the SAMD21 Pro RF will broadcast within the range of 902-928MHz in the Americas and in the range 863-870MHz in Europe. We reference the spectrum of broadcasting frequencies by its’ center frequency, 915MHz in the Americas and 868MHz in Europe. Ok, we have a general idea that we broadcast in a band of frequencies using a technology that translates data into radio signals, but how do we get from the SAMD21 Pro RF to the “Internet of Things”?
Broadcasting and uploading requires three things: a Node, a Gateway or Concentrator, and a Network Server. The “Node” in this case is the SAMD21 Pro RF, which will broadcast its information into the void and hope that there is a Gateway or Concentrator nearby to hear it. A Gateway or Concentrator will take the information your node is broadcasting and push it to a Network Server like the The Things Network or Resin.io. Let’s read that in a different way, the Gateway or Concentrator takes the radio waves, demodulates them (i.e. translates them), and puts that information onto the Internet. Neat! Now it’s here on the Network Server that we get to interact with that data. For a more in depth explanation about LoRaWAN, check out this great tutorial.”