Adding a digital to an analogic signal

[Simonx]

Hello,

I'd like to create a signal with a given offset (> 1V), all with RedPitaya.
I'm thinking of adding an alternative signal and a continuous signal.
For example: sending a sinus signal via the analog output, 100Hz frequency, amplitude 1V, added to the 3,3V continuous signal available on the digital output of RP.
Keeping this in mind, I tried to connected in series a 1,5V battery with a signal generator. I connected an oscilloscope and it worked.
Since I'm not sure about connecting two generator in series, I didn't try this with RedPitaya (I don't want to burn it!).
Could this work with RP or is there a risk to damage it ?
Do you have any idea about how to do this?
Thanks!

(since English is not my native language, there might be some misunderstandings... don't hesitate to ask for schematics!)

[Simonx]

Hello,

Sorry to bother you again but, does anyone have an idea?

[noah]

Hi Simon!

The thing you tried with the batteries and the generator does indeed work. But unfortunately that won't work with the RP. The reason: Your battery hasn't the same ground potential as the generator does, so you can hook up the battery's negative terminal to the positive output terminal of you generator (i assume this is what you did).

BUT on the RP you have only ONE ground potential. It is the same from the USB ground, through the supply ground (3V3, 1V8 and others) until the ground of outputs 1 & 2. So if you connect the ground of the 3V3 supply to the output of the generator, you shorten the outpu which will release the magic smoke of you redpitaya.

You could do the trick with the battery on the redpitaya or design an amplifier circuit that adds the offset.

I hope i expressed myself clearly to you

Cheers,
Noah

[Geoffrey]

I am no expert on electronics in the slightest but I might be able to point you towards some useful functions if you are new to the RP.

You could use the GPIO pins for your 3.3 V signal. From terminal you can use the 'monitor' function to simply set a pin to high. e.g. http://wiki.redpitaya.com/index.php?tit ... ifications

Then use the generate function from terminal to create your sine wave or alternatively you could use the WEB UI apps.

With regards to what the effect of combining these on the same channel would have on the hardware, I have no idea. This really isn't my area.

Apologies if you are working from a more advanced point than this and want more detailed help but I thought something was better than nothing.