Hello,
There are a few threads about communicating with la crosse weather sensors such as the TX4 and TX6. I have a TX7 sensor and I'm using an XY-MK-5V receiver.
I'm able to receive data from the tx7, but I've been unable to get any complete packets. I've primarily been working with the code from http://kjordahl.net/weather.html. I found some other information to leads me to believe that the tx7 and tx4 share the same timing and number of bits.
I think it might be too hard to debug my problem on this forum but for what it's worth, when I'm using the lacrosse.ino sketch, I never get anything showing on the serial monitor other than ""La Crosse weather station capture begin". The same goes when I enable DEBUG
I'm wondering if the XY-MK-5V receiver picks up too much noise? Would an RF protoboard from Freetronics be a possible solution?
I've read about people using audio interfaces and wave editors as oscilloscopes. The one part I wasn't sure about, and if you could confirm it... I can use an RCA cable and connect the data pin to one RCA plug and then plug this into an input on my audio interface? It took me several searches to find how people connect the interface to an RF board but I think this is it.
I have used this set up a number of times to analyse Weather station signals. Because we are looking at relatively high frequency signals (durations around 500uS etc) then these pulses are at the very limits of a computer's sound-card can track accurately. However we are usually aiming to get a general idea of what the signal waveform looks like to help write a computer program to do the heavy lifting. So if the waveform is not super crisp, don't panic! I have attached a suggested very simple circuit for you to try.
I have included a stereo system as I have found that handy at times (like a two channel scope!) but one channel maybe enough for your purposes (the 1/8" plug goes into the sound card "Line In" preferably, not "Microphone"). Note some laptop's audio in is only mono! The choice of 4k7:1k resistor divider is fairly arbitrary as it is desirable to have some sort of resistor between the computer's audio input, and what is being sampled, just in case a higher voltage than expected is touched. The reduction of the signal by two means the digital signal sampled will probably have a range of say 4 Volts, so reducing it to <1 Volts will also help protect the computer's sound inputs.
We are not looking to sample DC voltages at low frequencies so the existence of capacitors in the signal path is not important. Hence a simple resistance divider should be fine.
The impedance of the connection between the sound card and signal source needs to be fairly low as well if the response of the sound card to the higher frequencies is to be optimised. Hence the choice of a 4k7:1k resistor rather than the other more cautious users who use 1M ohm for example.
Audacity is a great cross-platform tool and can be left running and it just stores the signal. Then you can go back and find the bit of interest and enlarge it and clip off all the noise either side. I have found that a peizo connected across the output of of the 433Mhz Rx has been very handy as the chirps of the data are usually quite distinctive against the white noise. This can help pick up the areas of interest as Audacity is recording as well.
This is probably an over the top explanation for what you need, but I have found it very useful in the past and happy to pass the ideas on.
Cheers, Rob
(Edit: Thanks to jremington for the resistor ratio suggestion and Riva cleaning up the original .png)
PS if you connect the second probe to a pin on the Arduino you can toggle it while trying to decode the original signal, and you can see if your program timing etc is working as you expected on the Audacity recording.
Thanks for the response Rob.
I think you may have attached the wrong schematic, it looks like your png file is one that shows the tip/ring of a stereo plug. But I think I have a decent idea of where to go with this.
it looks like your png file is one that shows the tip/ring of a stereo plug.
That is correct. The plug goes into the line in audio jack on the laptop. Connect ground to the receiver ground and either A or B to the receiver output.
I use a 6:1 resistive divider (4.7K and 1 K), as the line in is intended for signals with a maximum of about 1 volt peak.
bcphysics:
Thanks for the response Rob.
I think you may have attached the wrong schematic, it looks like your png file is one that shows the tip/ring of a stereo plug.
The schematic picture is good but has an alpha channel so does not render correctly in some image viewers. I have attached a converted version so you can see it properly.
Thanks folks, I used Inkscape to draw it and spotted it was not right (ie had a transparent background) and I tried to fix in "GIMP" but obviously I still hadn't got it right. I like jremington's resistor range so I will edit the original post for any one who comes along later. I was not sure how much of the basics I needed to go over so I did not mean to offend any one. Thanks for the constructive feedback folks. Rob
jremington:
That is correct. The plug goes into the line in audio jack on the laptop. Connect ground to the receiver ground and either A or B to the receiver output.
I use a 6:1 resistive divider (4.7K and 1 K), as the line in is intended for signals with a maximum of about 1 volt peak.
My mistake! I was opening the png file in my browser and for some reason it was only showing the plug. I downloaded the file and it opens up ok and of course makes sense now. I just noticed the post above, I thought maybe the issue was a transparent background with the png
cheers!
