Quack! Quack! Its time for some RDF fun with LoRa (and HASviolet)

Joe NE2Z,  head of software development for the HASviolet project has been busy working on application specific use cases for our HVDN LoRa project along with the help of Steve K2GOG for user experience function feedback.

Function before feature

Many LoRa projects hit a roadblock after they reach basic objectives such as basic text chat between units where others such as the Disaster Radio go much further.

Since HASviolet has been initially built around a Raspberry Pi Zero instead of the various ESP32 boards, we are able to do a few things differently from a development perspective and most of which will port over to ESP32 based boards in the future. 

RDF:  To find the duck

Use any directional antenna suitable for 900 MHz or make your own by following our instructions for our open source design.

Here are some photos of the user interface that allows easy to navigate function selection without the need for a  SSH connection after initial configuration for things like messages, call sign, SSID and other parameters.

A more advanced version of the basic game involves a laser sensor to detect when someone is near by the Duck and it can either start quacking even more or stop transmitting just to annoy the hunter.

HASviolet: What color is your spectrum?

The entire United States amateur radio community are relative late comers to using or even understanding what LoRa is.

However, the "maker" community in the United States and elsewhere has embraced this weak signal spread spectrum technology much quicker and has been doing some interesting things with it.

This article will highlight where both communities of hobbyists can learn from each other and inspire some really nice projects enabled by LoRa technology thanks to HVDN's HASviolet project.

Black & White: What is LoRa?

Amateur radio or "ham" radio people usually love to talk about history and sometimes forget to look forward.

LoRa actually has some roots going back to the German radio company Telefunken and the underlying thinking of LoRa as a general concept was even described in part of a 1903 US patent by Nikola Tesla.

During World War II,  both the Axis and Allied powers experimented with "frequency hopping spread spectrum".

The smart minds of the day such as Leonard Danilewicz, Willem Broertjes and actress Hedy Lamarr being just a few to read about to learn the history of spread spectrum communication to help level up when it comes to learning about LoRa and technology like it.

While frequency hopping spread spectrum or FCSS can be useful for both data or voice transmissions,  only "chirp spread spectrum" or CSS is useful for sending short bursts of data over multiple frequencies.

This is one reason why the "maker" community has adopted LoRa because they generally care more about actionable use cases versus "talking for the sake of talking", which is what a lot of "ham radio" people enjoy most.

LoRa is not meant for voice transmission and it even requires some fancy manipulation to get it functioning for basic "chat" sort of communication.

The good news is that the HVDN team and our HASviolet project went a few more steps where others gave up when it comes to use case exploration.

The lack of voice communication via LoRa does not matter much for non-amateur radio users as other electronics hobbyists are more interested in using LoRa to relay sensor data or control the status of different devices, like a gate, mailbox or even as a fault indicator for a 3-D printer. But, not all amateur radio people use voice to communicate so this is ok.

The "Continuous Wave" or CW mode for short involves Morse Code and is still highly practiced within the amateur ranks today.

Even much newer modes  like WSPR, JT-65, JS-8CALL and PSK31 are some other choices with different use cases, but all really only focus on chat functions and not anything more use case driven beyond that. This now starts to make some amateur radio and maker people not very different from each other, aside possibly from age.

How to send LoRa:  Straight key optional

CSS also not only helps obscure messages as Hedy Lamarr exploited in her work more than 70 years ago with torpedoes and the US Navy, but also helps increase transmission range and control of torpedoes.

While encryption on amateur radio spectrum is not permitted, LoRa is easily demystified once you know how to look for the signals and decode them.  This makes LoRa and CW not really that far different from one another.

An amateur radio person may known Morse Code and a maker will not. Conversely, a maker may know how to probe packets and reassemble messages where someone who lives only in the ham radio world will not.

Perhaps the shared merit of LoRa and CW as  "DX" or "Long Distance" communication capabilities is worth exploring within amateur radio, but with value added use cases for a change beyond making contact for the sake of it.

This is where both communities can share and learn different skill sets and what HASviolet is all about.

LoRa implements CSS mostly in a default configuration which takes up about 250 kHz of spectrum,
but can be easily modified by changing the spread and bandwidth settings, which may be advantageous for certain applications.

This may sound crazy compared to sub 2 kHz wide CW signals, but LoRa can offer so much more.

What makes LoRa unique compared to other "spread spectrum" methods of transmission is that it is focused on relative narrow band use cases and thus better suited for sub-GHz spectrum use.

Comparatively, Bluetooth and Wi-Fi are also spread spectrum based, but use much wider bandwidth and would be troublesome to be used at frequencies such as 433 and 868 MHz as well as 900 to 928 MHz.   Since Bluetooth and Wi-Fi live at 2.4 GHz and above, this is a non issue since the higher you go in frequency, the shorter they travel when not including "Line Of Sight" communications.

The HASviolet project's goal is to utilize LoRa in the 900 to 928 MHz band also known as 33cm and to take advantage of the different characteristics this unique mode offers.

And because how well LoRa works very far into the "noise floor"  the communication distance when thought about as a function of transmit power, range and antenna size becomes pretty interesting.

There are ways to shrink the bandwidth which LoRa uses for single channel communication and will also be explored via the HASviolet project too at a sub 6 kHz levels and possibly even further with correct precision timing.

LoRa: Made better with fruit?

One major challenge with LoRa is that it uses proprietary modulation offered by Semtech and is not considered an "open source" mode like what NB IoT uses, which is a competing wireless standard along with SIGFOX as popular "Internet of Things" type of applications that commercial and maker enthusiasts are using.

A company started in 2005 by Lady Ada (Limor Fried) called Adafruit Industries helps the educational "STEM" and maker communities through open source development of fully functional and semi-complete products which incorporate components made by company like Semtech.

The modern electronic hobbyist or "maker" can easily purchase what Limor and her team creates and use them in any number of projects, just like our HVDN HASviolet project.

And there is one thing that the "ham radio" community really loves, and it is anything that involves "low cost".   LoRa easily becomes a low cost way to experiment with something very fun.

A side benefit beyond cost is that it makes a perfect platform to start the "ham radio" crowd to essentially start to "level up" on some areas of interest that the maker crowd has already zoomed far ahead on. Some of these include things to do with "Raspberry Pi",  "ESP32", "MicroPython", "IoT"

Full integrated Semtech LoRa chips such as the SX1276, SX1272 and SX1261 can all be generally had on preconfigured breakout boards for under $10 USD, so lets dive into what each community can learn from each other in upcoming articles.

So what is HASviolet?

When the HVDN HASviolet team came up with an idea to make something which the maker and amateur radio community could use together,  they started thinking about how to highlight underused spectrum where licensed and unlicensed users may overlap.

Originally, the amateur 50-54 MHz "6m" band and its nearby unlicensed 49 MHz spectrum was thought to be a good starting point due to the ability to easily design something that could use the popular Raspberry Pi with an add on RF filter board.

This proved pretty quickly even after discussion with other amateur radio enthusiasts as far away as Arizona and Germany to not be a path to start down first as others have done it, but failed to get a lot of interest.

Instead, it became clear  that going much higher in frequency would still offer what the HVDN team was looking for.

We would like to introduce you to the HVDN backed HASviolet project, our journey and lots of great documentation to inspire others to come along for the ride using violet shared spectrum.

If you want to learn something cool involving hardware, antenna or software, we think you will like what you are about to find.

HASviolet Team

• Joe Apuzzo N1JTA - General Do'er & HASviolet HW Certification Guy

• Steve Bossert K2GOG - Antenna & RF Design Lead & UI/UX Hamster

• Joe Cupano NE2Z - Core Software Developer & Git Hub Jedi Master

HASviolet General Details

• General Information -  https://hvdn.org/violet 

• Git Hub Repository - https://github.com/hudsonvalleydigitalnetwork/

HASviolet: Pi Power Considerations

To help celebrate International Pi Day,  the HVDN team would like to share a tiny preview related to our HASviolet project we were expecting to release at the WOPR Summit later this month.

Unfortunately, the blasted COVID-19 virus forced the event to be rescheduled for September 18th to 20th, but we are keeping our project goals on track for release since we have even bigger plans for HASviolet for the rest of the year!

What is HASviolet?

Our project goal was to create an educational platform involving (H)ardware selection, (A)ntenna theory and (S)oftware involving LoRa communications as well as other FSK, GFSK, MSK, GMSK and OOK modulation method applications in the future.

The letters in the word "HAS" may make more sense now, but the color "violet" needs a little more explanation.

We want to promote the use of  900 MHz and above spectrum for both amateur radio and "IoT" hobbyist use so we chose the frequency of 911.250 MHz as our initial project center frequency and namesake.

The HEX value of 911250 is a nice shade of purple and hence, how we came up with the second word in our project name - violet!

Our hopes are that this frequency can become the epicenter for amateur radio experimentation involving LoRa in the United States.

Hardware needs power! 

Releasing this article "just after"  March 14th (AKA "Pi Day") should make our readers guess that our HASviolet project involves the popular Raspberry Pi embedded computer and indeed it does!

You need to have reliable and stable power  for all Raspberry Pi projects and that is what this article will talk about, but just in the context of the Raspberry Pi Zero Wireless device since that is what we are using as part of  the HASviolet project.


Plug in the wall options

The "current" requirements for a Raspberry Pi tend to be at least 2 amps of power and it is advised to use a mains power supply rated at least for 2.5 amps.

Reliable sellers such as Adafruit, SparkFun, MicroCenter, Fry's and even Best Buy or Barnes & Noble in the United States have already ensured what they sell will provide the best user experience.

                      

However, it is a good idea to be cautious when making a purchase online via websites like Amazon or E-Bay since sometimes it is harder to know what you are buying from online sellers.  The best price does not always guarantee the best product!

Here is a list of HVDN approved AC mains 2.5+ amp power supplies from select sellers who sell both online as well as through traditional stores you can visit:

• Adafruit 5V USB Micro Power Supplies 

• SparkFun 5V USB Micro Power Supplies

• Micro Center 5V USB Micro Power Supplies 

• Argon ONE  5.25V 3.0 Amp via Amazon.com 

• CanaKit 5V USB w/switch via Amazon.com 

USB power bank options

A USB power bank is probably one of the best options to power your Raspberry Pi project since you can charge them for portable use by using your plug in the wall adapter or even charge them from any USB port such as one found on any computer.

• You do need to be sure that your power bank is capable of outputting over 2.0 amps of current on at least one of the USB output ports.

• Some USB power banks will indicate this clearly, so be careful about what you purchase.

• A minimum 10,000 mAh capacity power bank is recommended, but 20,000mAh is better.

Higher battery capacity means longer run times. If you plan to travel by air, there is a limit on how large of a power bank you can take with you. Please check airline or local government regulations for details.

In the United States, the FAA sets the appropriate restrictions which the TSA is responsible for enforcing.

In order to match your Raspberry Pi, you will also want one with the USB micro connector rather then the newer USB-C connector so you can use your existing wall mains supply to run your Raspberry Pi directly or to charge your power bank.

Here are three common options to consider purchasing:


HVDN Recommended Option 1: INIU 20000 mAh with  3.0 A output plus USB micro and USB-C input via Amazon.com

HVDN Recommended Option 2: USB Battery Pack for Raspberry Pi - 10000 mAh plus dual high current USB

HVDN Recommended Option 3: Baseus PPDMNA USD PowerBank - After extensive research by one member of the HVDN team, this power bank has proven a good value for the money and comes in different colors. This power bank is also very thin. It can also be shipped from different countries for no extra cost.

This power bank offers true USB-C standard for both charging or output.  A micro USB connector for charging is included alongside the standard USB connector to power external devices.

 

HVDN USB Power Bank Recommendation

There are far too many power bank options available today and we are only sharing three options.

Our recommendation is option 3 based on price and feature set plus you can even get it in pink or blue aside from the usual black or white colors.

Option 1 is great if you need higher capacity and fancy display plus two USB outputs.

Option 2 is is worthwhile if you are looking to add items to your Adafruit shopping cart, who is one of the main suppliers of components found in the HASviolet project you will be able to learn about later this month (Spoiler: Saturday March 28th at 9:11 AM)

pHat Power Options

Modular boards that have the same foot print and 40 pin connector that matches the Raspberry Pi are often referred to as a hat or pHat. A pHat can go under or on top of a Raspberry Pi when using the correct 40 pin connector.

Example of a pHat by pimoroni.com and sold by Adafruit.com.
The EnviroPhat is a collection of sensors with more detail found here

There are many pHat's available for different tasks, but only a few made that can provide a reliable portable power supply.

Here are some options with commentary on ones designed to work with a Raspberry Pi Zero.

pHat Power Option 1:  PiZ-UpTime 2.0 - Not to be confused with the original PiZ-UpTime which only ran on a single 14500 LiPo battery.

The new 2.0 version offers no such restriction and also adds better external on/off control, power in and power out connections along with a fuel gauge to safely power down your RPi when the battery reaches a low amount.

Further details here. The second picture is the first generation PiZ-UpTime for comparison and is not recommended.

Genuine PiZ-UpTime 2.0 

Here is the original PiZ-UpTime for comparison and to show the genuine product compared to imitation copies mentioned later in this article.

pHat Power Option 2:  PiSugar Portable Power Platform - Some members of the HVDN HASviolet team like this product because it is open source as evidence by its Git Hub project page and its overall set of features.

There are two different side batteries available that are the same size of the board and RPi Zero.  A nice feature is a built in visual battery capacity meter via 4 blue LED and the use of the power pads on the bottom of the Raspberry Pi Zero. The PiSugar can also function as a UPS.

3-D printer files are even available to help create different cases easily or to modify for your own use.

Both the 900 mAh and 1200 mAh versions can be purchased via Amazon.com.  The only only drawback of the PiSugar is the small size of its battery which will limit run time compared to a larger power bank.

One member of the HASviolet team has used the 1200 mAh version of this product and easily got 5 hours of continuous run time while running the "beacon" mode of our project with a transmit interval of once every 5 seconds.

pHat Power Option 3:  Generic UPS Power HAT  - There are many generic UPS power hats available for the Raspberry Pi Zero and we have only tested two.

The first one was a generic version of the PiZ-UpTime original product and was a waste of money.

A few years ago, a counterfeit version caused a fault with a Raspberry Pi Zero and was unable to be used for anything else ever again, including the RPi Zero! Please avoid purchasing this product!

The second generic UPS pHat worked much better but only lasted about an hour which was strange considering the PiSugar worked for much longer with a not much larger battery. This one also uses pins from the underside to power your Raspberry Pi.

What to expect from HASviolet?

We hope this brief article on power sources for the Raspberry Pi Zero has you curious on what are we building for the HASviolet project.

Our team thinks that people will want to use the HASviolet project both at home and while traveling, hence us starting to make sure power solutions are something you are already thinking about.

Between now and Saturday March 28th, we will release some additional articles focused on the antenna part of the project along with details relating to Git Hub and other basic necessities so that you can start putting aside some hard earned money to buy the needed hardware for HASviolet!

Be safe in the meantime if you are under self-quarantine or in areas overly affected by COVID-19.

Thanks!

HVDN HASviolet Team

(Joe Apuzzo N1JTA,  Steve Bossert K2GOG & Joe Cupano NE2Z)