DG1000Z and arbitrary function

[vsavic]

Hi all,

I'm playing with my first fn. generator and I have a question about it (I hope this is the proper section).

I want to simulate UART signal for some simple message for example "HELLO".

So, I transformed this message to this hex:

20002000200020003000200020003000200030003000 20003000200030002000200020003000200030003000 20002000200030003000200020003000200030003000 20002000200030003000200020003000200030003000 20003000300030003000200020003000200030003000
H                                             E                                              L                                               L                                            0

(Hex file is normal with little endian format, here I just separated it like this to be easier to read it).

And then I saved that as RAF file on USB and loaded it as arbitrary function on DG1022Z.

So, I'm getting on my oscilloscope square signal, but I'm also getting negative voltage before my square pulse and after that. Why is that?
And also, I'm guessing that's the reason why I'm not able to decode this signal on my oscilloscope?

[LaurentR]

First thing, on your AWG, you need to set up the amplitude of the signal. By default AWGs tend to be set up for 0V-centered AC signals (1 or 2 V peak-to-peak).
So find the option to set the amplitude and offset so that your waveform is between 0 and Vmax of your choice (Vpp = Vmax, offset = Vmax/2).
Alternatively, there is probably a mode to enter Vmin and Vmax directly.

Now you should see a more traditional TTL/CMOS signal that bottoms out at 0V.

[vsavic]

Thanks for your reply LaurentR, this solved one part of the mystery

But for other part of this mystery, when I changed the frequancy to 9600 to match the baud which is set on my oscilloscope I ended up with signal which does not look like digital signal (no squares), so it looks like for every 1 and 0 that I'm sending I need to readjust the sample rate.

But I couldn't find in doc. if I can specify that somewhere in file header or not, or just to "duplicate" data, so instead of having 1 0 1 0 for example to have 111 000 111 000 in order to get square signal?