Let's Make Robots!

You may not need an oscilloscope!

Want to see what's going on? Even with "history" and zoom? Make a simple cable, download a free program and..

Aparently there are some problems with the images in this one. Since the images are not THAT important for you to get the point, I take the liberty to just direct you to the albom they are in, in case some are missing on your monitor:

http://picasaweb.google.dk/fritslyneborg/SoundrecordingAsDebugging#

Sorry & thanks for understanding ;)


 

Step 1:
Localize your computers audio in. If it has both Mic and Line in, use the Line.

Step 2:
Find a jack or whatever fits into the port, and in the other end find3-4 wires. If you have 4, 2 of them are ground, if you have 3, one is ground, and you need to split that in 2. The other 2 are Left & Right:

IMG_6174.JPG

 

STEP 3:
At the other end of the wires, make whatever you like; Point is that you will have to be able to hook this up to anything, if you do not want to solder every time you use this tool. I mae up some multi-thingeys that can be plugged / unplugged, and hooked up to anything:

IMG_6175.JPG

 

Step 4:
Download a soundrecording tool that can show the 2 channels next to each other.

 

That's it!

To use this, plug in the cable to your computer, turn down recording level / put it on Aux / Line, not Mic, no pre-amp.

You can now measure 2 Logic Level signals at once (or just one) and compare them.

 

EXAMPLE ONE

As you may know, it is possible to buy extremely cheap radio recievers and transmitters. Theory is, that you can send serial signals from one Microcontroller to the other, wireless.

i reality, it has often proved very hard to get a steady signal going. Now check this:

On Picaxe, here is first this code used on the sending part:

Billede_2_0.png

I hooked up the cable made as shown above like this: Ground to ground on both units. Data in on reciever, Data out on sender. And this is what I got:

Billede%201.png

Oops - something is wrong!

Signal is send, but nothing is recieved!

Now without the debugging-tool, it could have taken me a long time to find out what was going on. I hate serial for the fact that it is so hard to debug.. well untill now ;)

Ok, I hook up again, fixin all loose connections, recieving is shown on top, sending is shown at the bottom:

Billede%203.png 

Oh, the reciever is sending a lot of noise to the Microcontroller at first, so the Microcontroller cannot tell when the serial signal is starting!

Well then, let's modify the code:

Billede%207.png

- And see:

Billede%202.png

Well, from a distance, we can see that the sender is generating noise if left to hang high! Will fix that later, by using other combinations of T/N of the serout.

But first, let's zoom in, and see how the signal on the reciever is now first made steady, so the MCU can understand when to start listening:

Billede%208.png

- and even closer:

Billede%209.png

 Bingo!

 


OTHER EXAMPLES:

Now, what I'd like to see is your examples, please send them in below if you have any.

 

If nobody sends in anything, when time, I will try to have a look at:

A: LED shining on..
B: LDR

A: PWM out of an EZ ultrasound
B: Analoge out of an EZ ultrasound

.. and more to come :)

 

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hail fritsl

i did experiments with audio in too

there are may  free software oscilloscopes build to work with audio in of the pc

i used them with success for some time, they can trigger and lock periodic signal and have all feature of a normal oscilloscope...

remember to chop input signal using diodes to prevent overvoltage which can damage audio in

 

the only big problem with this solution is that audio-in are band-pass filter which limit visible signal  in the audible  band...

anyway the benefit/cost ratio is a division by zero :) 

Oh yes, thanks, I completely forgot in this post; The Software Oscilloscopes.. Yes, you are right, if you want an oscilloscope, you can use it like that.

problem with them is, that you cannot do what is done above; History! it would be absolutely impossible to debug and see why the first bit of a signal was not counted for as a serial signal. 

No way you could do that with an oscilloscope as far as I know?!

But extremely easy if you sample it.

For more of my reasoning, please see my original blog-posting about this.