Over on his YouTube channel CWNE88 has posted how he has been using and RTL-SDR with the rtl_433 software to explore the data coming in from various 433 MHz ISM band devices in his neighborhood. In the video he explains how he has set up rtl_433 on his Raspberry Pi, and what sort of data he is receiving. Some examples of devices he's received include various weather stations, doorbells, remotes and car tyre pressure monitors.
He also mentions how these signals are unencrypted, noting that in a future video he will show on GNU Radio how a false signal could be synthesized.
Nimrod makes his own sourdough and wanted a way to track the temperature and humidity of the bread making environment. To do this he's set up a system involving rtl_433 on a Raspberry Pi which live streams all of his home temperature/humidity sensor data into InfluxDB. The program rtl_433 is software for the RTL-SDR that allows users to receive data from many different brands of home weather/temperature sensors, as well as many other wireless ISM band devices. InfluxDB is a type of database that specializes in storing and displaying time series data from sources like sensors.
The chain of data starts with rtl_433 which collects the temperature sensor data via an RTL-SDR. The output of rtl_433 is sent to Mosquitto, an MQTT messaging protocol server. A program called Telegraf then subscribes to the MQTT queue, and parses and transmits the metrics to InfluxDB. InfluxDB finally records the data, and provides graphical plots.
Nimrod's post is a full tutorial showing how to download and set up each of the programs used in the system, and how to view the data collected with InfluxDBs graphing system.
To keep them away from humid air Scott uses "PrintDry" plastic vacuum canisters. Unfortunately he found that the vacuum sealing system wasn't perfect, and that some canisters would lose their vacuum after a few days. In order to ensure that the canisters were properly sealed he decided to add some active monitoring with pressure and humidity sensors and a wireless transmitter.
His monitoring system consists of a cheap 315 MHz ISM band transmitter, ATTINY85 microcontroller and pressure + humidity sensor. To receive and monitor the data he uses an RTL-SDR that runs the rtl_433 software, which is a program that is capable of decoding many different types of wireless ISM band sensors.
DIY Wireless Temp/Humid/Pressure sensors for measuring vacuum sealed 3d printed filament containers
Over on his YouTube channel Tech Minds has recently uploaded a video that demonstrates and shows how to use the rtl_433 software with an RTL-SDR to decode 433 MHz ISM band low power devices. Typically these devices include things like home wireless temperature and weather sensors, tire pressure sensors, remote controls, and other various sensors.
In the video he sets up an RTL-SDR and magmount antenna by his window and is able to receive data from several of his neighbors weather stations, and some car key remotes. He shows how to run the software on both Linux and on Windows.
How To Decode 433Mhz Low Power Devices Using RTL433 And A RTL-SDR Receiver
SimpliSafe is an American DIY home security system company that claims over 2 million customers. Their system relies on 433/315 MHz ISM band wireless radio communications between its various sensors, control panels and remote controls. Back in 2016 we already posted about research from Dr. Andrew Zonenberg and Micheal Ossmann who showed that the SimpliSafe wireless communications are unencrypted, and can easily be intercepted, decoded, and spoofed. SimpliSafe responded to those concerns by downplaying them and mentioning that sophisticated hardware was required.
Adam began with some initial manual RF analysis with an RTL-SDR, and then later worked with rtl_433 dev Christian Zuckschwerd to add PiWM demodulation capability, which is the modulation used by SimpliSafe systems. Now Adam is able to easily decode the serial number, pin codes, and status codes transmitted by SimpliSafe sensors and key pads in real time with just an RTL-SDR.
This is very concerning as not only could a burglar easily learn the alarm disarm pincode, but they could also profile your behavior to find an optimal time to break in. For example if you arm your alarm before bed, and disarm in the morning your sleep schedule is being broadcast. It is also possible to determine if a particular door or window has been left open. With a tuned Yagi antenna Adam was able to receive signals from 200+ feet (60m) in free space, and 115 feet (35m) through walls.
In addition to the lack of encryption, Adam also discovered that the SimpliSafe system was susceptible to jamming attacks, and that the tamper detection system can be easily compromised. Adam has disclosed all concerns and findings to SimpliSafe who are aware of the problems. They assure him that next generation systems will not suffer from these flaws. But unfortunately for current generation owners, the hardware will need to be eventually replaced as there is no over the air update capability.
Rtl_433 is an RTL-SDR compatible command line based tool for monitoring various 433 MHz ISM band devices, such as temperature sensors, weather monitors, TPMS, energy meters etc. A full list of support devices can be found on the rtl_433 Github.
Over on his blog “raspberrypiandstuff” mentions that he’s been using rtl_433 and an RTL-SDR on a remote headless Raspberry Pi to receive and monitor temperature and humidity from his weather station. From the data he’s able to produce some nice graphs that show changes over time.
However, one problem that he ran into was that the USB controller on the Raspberry Pi would sometimes hang. The only solution he’d previously found to fixing it was to physically disconnect and then reconnect the RTL-SDR. But now “raspberrypiandstuff” writes that he’s found a new solution which is to use a small C-program called usbreset.c. Combined with a bash script that detects which device the RTL-SDR is on the bus, this tool helps to automatically reset the USB on the Pi if it fails to keep the RTL-SDR logging 24/7 without physical intervention.
This may be a solution to look into if you’re experiencing similar issues with 24/7 monitoring on the Raspberry Pi. If you’re also interesting in rtl_433 monitoring, “raspberrypiandstuff” also has a post on creating a simple GUI for rtl_433.
Gough shows how he was able to receive and decode the data from an Aldi weather station device and a wireless doorbell transmitter. He also was able to modify the rtl_433 code slightly to produce a CSV log file of the temperatures that were received and decoded from the weather station.
The Raspad 3.0 is a portable tablet enclosure for the Raspberry Pi 4B. It comes with a high resolution 1280 x 800 10.1 inch touch LCD screen, built in speakers, built in battery and a plastic enclosure that houses the LCD driver board and Raspberry Pi. Accessible on the side of the enclosure are the USB, HDMI, ethernet and audio ports which connect via the LCD driver board. They also include an accelerometer shim which allows the screen to autorotate.
A few months ago SunFounder, the company behind the RasPad 3.0 reached out to us and asked if we wanted to review the product with a free sample. Normally we don't review products unrelated to SDR like this, but given the amount of RTL-SDR software available for the Raspberry Pi, and what appeared to be sufficient internal space, we were curious if there was a way to turn this into a portable RTL-SDR tablet...
A few weeks ago the Raspad 3.0 arrived, well packed and with all the advertised components. Note that the Raspad 3.0 does not come with a Raspberry Pi 4B, this is something you will need to provide on your own.
Inside was a mains power cable, 15V DC power brick, two HDMI jumpers, a USB jumper, accelerometer shim, SD card ribbon, small 5V fan, heatsinks for the Pi, screwdriver and mounting screws, a manual and the RasPad LCD screen itself.
Assembly is straight forward. You unscrew the enclosure using the provided screw driver, insert the Pi 4B, screw it down, connect all the cables from the Pi to the LCD driver board and SD card slot, then reassemble. After inserting the Raspberry Pi 4B and attaching all the cables this is what the inside looks like.
Now we could have reassembled the enclosure here, but we wanted this to be a portable RTL-SDR tablet, with the RTL-SDR and an SMA antenna port built in.
It turns out that the best way to fit in an RTL-SDR Blog V3 is to directly connect it to the spare USB port on the Pi. You might also consider using a micro style RTL-SDR which would fit more easily, but those do tend to get quite hot in a small package, and can be quite bad with internal noise. Also good shielding is probably quite critical in this application due to the dongles proximity with the LCD driver board which could be an RFI source.
The SMA side of the RTL-SDR Blog V3 rests nicely on top of the USB port of the LCD driver board providing some stability, and when the bottom lid is assembled there is plenty of clearance and no squashing.
Next we drilled a hole on the rear wall of the bottom half of the enclosure for the SMA female port, and tightened the SMA connector down with a nut. In the future we'll be upgrading this to a long barrel style SMA female connector, as a regular SMA female connector is a bit short. Then a short well shielded SS405 coax cable was used to connect to the RTL-SDR dongle.
ProTip: Do take care to remember to remove the SD card when disassembling the RasPad! If you don't you'll end up with the SDcard slot getting ripped from it's ground traces. This happened to us, but we were able to easily solder it back on. There is a sticker on the backside of the enclosure warning about this.
Software & Testing
SunFounder provide a custom Raspbian distribution designed specially for the RasPad. However, we decided to instead install the DragonOS Pi64 Distro which is an Ubuntu distribution for the Raspberry Pi 4B that has many built in SDR programs. We burnt the image to a SD card, inserted it on the side, plugged the Raspad in to the power connector, and held the power button down for a few seconds to turn it on. Despite a few initial error messages saying it cannot enable the USB ports, everything eventually booted just fine.
We then plugged in a cable going to one of our multipurpose dipole antennas mounted just outside the office window, and tested both SDR++ and GQRX. In both cases we were immediately able to connect to the RTL-SDR and receive signals with signal strength equivalent to that received by our desktop PC, indicating that LCD interference was not a problem.
The resolution of the screen is high enough and images and text are clear. The screen is also decently bright, and brightness can be adjusted using the buttons on the side.
DragonOS Tablet Compatibility Issues & Fixes
As DragonOS is not designed for a tablet setup, there were a few bugs. It should be noted however that these issues are not a reflection on the Raspad hardware, as obviously the official Raspad OS will not have these issues as it's designed specifically for tablet use.
We initially had no sound in SDR++ from the built in speakers. After some troubleshooting we managed to get sound by disabling the headphone jack in the audio mixer settings, which appears to be the default output in DragonOS. To do this, click on the speaker icon on the bottom right task bar and click on Mixer. Then go to the Configuration tab and uncheck the second Built-in Audio entry. Close it, and open SDR++.
In DragonOS the touch screen works fine, although it is difficult to click on small buttons. There is no onscreen keyboard available by default. We couldn't find a way to enable a tablet mode in DragonOS, so instead opted to install an onscreen keyboard called 'onboard' via 'sudo apt install onboard'. The accelerometer is also not enabled in DragonOS. We did not attempt to fix this as we have no need for screen rotation.
LCD screens are well known to be sources of RF interference, and putting an SDR in close proximity to one could result in the spectrum being very noisy. However, without an antenna connected we did not notice any interference across the spectrum from the LCD screen. It appears that the LCD RFI noise levels are not too bad, and the shielding on the RTL-SDR Blog V3 and the coax jumper cable is good enough to prevent any being received. When an antenna with a few meters of coax was connected (such as a magwhip or our portable dipole) we also didn't notice any LCD interference.
However, when a SMA telescopic antenna was connected directly to the SMA port we did start noticing the telltale spikes across the spectrum that are typically generated from LCD screens. If the magwhip or dipole was also moved within 2-3cm of the LCD screen, we also saw these interference spikes appear.
So it would be recommended to use a magwhip or dipole that has a coax run that can sit a few centimeters away from the screen. This limits the handheld ability of the RasPad a little, but you'd probably want a magwhip, dipole or other antenna over a directly connected telescopic whip for better reception anyway.
We tested a worst case scenario, with the RasPad running the RTL-SDR and SDR++ continuously at the brightest screen setting. With this test the battery lasted 2 hours and 10 minutes from a full charge. Presumably if the screen was dimmed and turned off for some periods of time, it would easily last 3-4 hours.
The total weight of the Raspad including our mods is just under 1 kg (2.2 lbs). About double the weight of a modern tablet, but still light enough to be easily carried.
The small 5V fan provided in the kit is unfortunately a bit noisy, and it's cooling ability is seems limited. We've seen these small fans on other Raspberry Pi cooling accessories and found that they are next to useless at cooling. It would be good to see a slightly larger and quieter fan, or perhaps a better passive cooling heatsink.
The power brick output is 15V, 2A. Ideally we would be able to charge the RasPad via a car/boat 12V connection as well. We're awaiting a response to see if this is possible. Update: Unfortunately 12V seems to be a no-go, quoting SunFounder "the 12v supply may cause the Raspad to fail to charge, as the minimum is 15v".
The RasPad 3.0 in our opinion overall a good product. It allows you to easily go portable with your Raspberry Pi 4. While it was designed for other projects, there was just enough hackability left in it for us to fit a RTL-SDR Blog V3 and antenna port into the enclosure, yielding us a clean and portable SDR solution.
With at least 2 hours of battery life when running an RTL-SDR and software, we can easily see this being taken out in the field for spectrum analysis, decoding with rtl_433, or for portable listening to the airband, trunking etc. However, some customization of DragonOS or the RaspadOS is going to be needed to get the most out of the touchscreen.
There are also alternative LCD screen products designed for the Raspberry Pi where you sit the Raspberry Pi on the back of the screen. But it's unclear if there would be enough space inside to fit an RTL-SDR, and not to mention the lack of a battery. We also previously reviewed the Elecrow CrowPi which is somewhat similar, but a lot more clunky if you're just after a pick up and go portable SDR tablet solution. There are also higher end higher priced laptop style enclosure products for the Pi, like the Pi-Top but we're unsure if they're likely to fit the RTL-SDR internally this easily.
Disclaimer: We do not receive any compensation for this review apart from a free Raspad 3.0.
We also recently came across this review from German YouTuber Manuel Lausmann who installed and ran SDR++ on the Raspad with an SDRplay RSP SDR.