I have a hot tub.
I have a fear that one day the hot tub will quit heating.
I have a fear that when it quits heating it will freeze over and crack.
So I’ve been living in fear for a few years until last week when I discovered 433 MHz devices.
So I took a chance and bought this pool temperature sensor:
I’ve been dabbling with 433 MHz devices over the past few days and tying those devices in with my home automation software named HomeAssistant. A decent transmitter receiver kit will set you back a whopping $10 or so. I opted for this one.
It performs extremely well in a home environment and has great specs.
One of the gotchas of this device though is it comes with ABSOLUTELY NO DOCUMENTATION WHATSOEVER. You’d be hard pressed to find much useful on line as well. So that’s where I come in.
Fortunately the wiring is pretty basic and the pins are clearly marked on the back side of the circuit boards.
Did you ever stop to think about all those radio waves flying around us all the time? Of course you didn’t. That’s why you have me!
I have what I consider to be a pretty extensive Home Automation setup.
I use the program HomeAssistant on a Raspberry Pi3 with an Aeotech ZWave controller . Also I have some wifi devices such as a Nest Thermostat, Ring Doorbell, Ethernet Security Cameras, a WiFi Light Switch, and some smart light bulbs.
Was walking around Target and saw an inexpensive remote outlet which I was pretty sure I could perform the Replay Attack on.
The Replay Attack is when you record a signal from something and transmit it back to perform the operation.
These devices typically transmit around 433 MHz and have no encryption of any kind whatsoever. Just a simple transmit burst for on and off functions.
Ok I’ve been on a roll playing with OP25 and Raspberry Pi and one thing I can tell you is that the onboard audio from the bcm2835 chip is somewhat inadequate. Oh, it works but you’re going to need a powered speaker or really efficient headphones, and even then it is a bit light.
What to do?
Add a USB Digital to Analog converter (DAC). Depicted here is a HiFiMeDIY USB DAC. This is a tad bit expensive for this project but I have like 4 of these things laying around the house. They are ridiculously good. If you like music slap one of these bad boys on your laptop in the hotel room and the quality of your music will improve ten fold.
That’s not what we’re doing here though.
There are a LOT of USB DAC’s out there and some cost just a few dollars. HiFiMeDIY makes some cheaper ones as well that are way more than enough for improving your OP25 sound.
The Phat DAC costs $15 but you’ll have to solder header pins on yourself. That may be the cheapest, and best route. It has the form factor for the Raspberry Pi Zero but it works on all the Pi’s.
In my last part I set the Pi up to stream to Broadcastify. In this one we are just going to pump audio out through the headphone jack.
I’m doing this with an old generic black RTL-SDR and it works and it works fine but it is kind of susceptible to heat and cold and the ppm correction drifts a bit. I really recommend getting a v3 RTL-SDR or a NESDR Smart as they seem more stable. At any rate it doesn’t matter, you’ll just have to deal with the drift if you have any.
My assumption here is that you have Raspbian installed on at least a Pi 3. I haven’t tried it on a lesser Pi but I had it on a Pi 3 B + and then I found a couple Pi 3 B’s laying around and figured I’d reclaim my B+ for another project on another day. OP25 runs fine on the Pi 3.
So I finally figured out OP25 and I have this brand new Raspberry Pi 3 B + laying around doing nothing. In this segment we’ll install OP25 on Raspberry Pi and then take our police scanner feed and send it to the internet on Broadcastify.
As someone pointed out to me yesterday, “There’s an app for that” they are indeed correct. You can get Police Scanner Apps for IOS and Android. Guess where the feeds in those apps comes from? If you said Broadcastify you’d be correct. So if no one is feeding your municipality then there will be no feed in the app. We will be that feed.
So the assumption is that you have a Pi with Raspbian installed and you kind of know how to use it.
OP25 is a program that decodes P25 Phase 1 and Phase 2 digital radio. Some municipal areas are upgrading to P25 Phase 2 so almost gone are the days that you can track them with a police scanner since P25 is a Trunked Radio system and not just a lone frequency to monitor. The only things that do Phase 2 are hardware scanners and hardware radios and OP25 for software radios. Bear in mind Phase 2 could be encrypted and nothing you can do will decode it.
OP25 is HARD. I’m a geek and I messed with it on and off for a year or more and it whipped me more than once. Now that I have it working I find that it is REMARKABLY easy and I’m mad at all the geeks out there who never made a simple tutorial. There are tutorials out there, some good but everybody leaves out the good stuff or the stuff they took for granted.
First you need to download the latest Raspberry Pi Raspbian OS from here. Get whichever version you want but I like to get the desktop version so I can VNC into it as it makes it easier.
If you have never done this connect your Raspberry Pi to a monitor, keyboard and mouse. If you are an old salt with Linux then just run headless and SSH into your Pi.
Once you download that file UNZIP IT. UNZIP IT. The file will end with an extension of .img
Do NOT try to burn the zip file to your SD card. UNZIP IT AND GET THE .IMG FILE.