latest project.
fast enough for audio work.
waiting for pcb.
software mostly done.
fast enough for audio work.
waiting for pcb.
software mostly done.
An externally hosted image should be here but it was not working when we last tested it.
pcb's came today.
built one up.
got software running but signal on screen was noisy.
turns out a2d doesnt like you reading it close to clock edges.
so put a couple of padding instructions between clock changes.
doesnt look bad now.
i am getting 11 mega samples/second.
built one up.
got software running but signal on screen was noisy.
turns out a2d doesnt like you reading it close to clock edges.
so put a couple of padding instructions between clock changes.
doesnt look bad now.
i am getting 11 mega samples/second.
Built up another pcb today but took my life in my own hands and used a cheap copy Chinese A2D. Display was very noisy when displaying fast signals.
Tried to play about with clock signal edges to improve it but couldnt.
So removed Chinese part and fitted genuine AD part and 90% of the noise just disappeared.
Moral of the story is don't expect Chinese parts to perform the same as genuine parts.
Tried to play about with clock signal edges to improve it but couldnt.
So removed Chinese part and fitted genuine AD part and 90% of the noise just disappeared.
Moral of the story is don't expect Chinese parts to perform the same as genuine parts.
Got 3 built up now, enough to compare.
The display is clean for an A2D scope.
Pleased with it.
Next project is a 20MHz sampling scope using AD876JR.
Sticking to SOIC packages as they are easy to solder.
The display is clean for an A2D scope.
Pleased with it.
Next project is a 20MHz sampling scope using AD876JR.
Sticking to SOIC packages as they are easy to solder.
Built up my 20 mega samples/s scope.
It worked very badly.
I then realised the a2d is running off 5 volts on the analogue side and was expecting up to 4.6 volts in. My front end op amps run off 3v3 so didn't quite make it.
So I rejigged the a2d's reference voltages to be 1.6v (as before) and 3.3v (adjusted down from 4.6 .) Had to reduce the gain of the front end by a factor of two and then it all worked fine.
It worked very badly.
I then realised the a2d is running off 5 volts on the analogue side and was expecting up to 4.6 volts in. My front end op amps run off 3v3 so didn't quite make it.
So I rejigged the a2d's reference voltages to be 1.6v (as before) and 3.3v (adjusted down from 4.6 .) Had to reduce the gain of the front end by a factor of two and then it all worked fine.
The Ad9220AR A2D is relatively easy to use.
The AD876JR is a little harder to use. It requires a dual RRIO op-amp to produce low impedance upper and lower A2D reference voltages. It also seems to vary from one chip to the next. I have to use a pre-set to set centre voltage of signal coming in.
The AD876JR is a little harder to use. It requires a dual RRIO op-amp to produce low impedance upper and lower A2D reference voltages. It also seems to vary from one chip to the next. I have to use a pre-set to set centre voltage of signal coming in.
Built up a 20 megs sampling scope today.
It seemed a bit inaccurate, not a massive amount but enough to not look right.
Started changing resistors to make it more accurate but couldnt get it right.
Then realised my pc software uses 4 divisions in the Y direction while voltage into a2d is 3.3. I had forgotten to scale pcb screen to reflect this.
It seemed a bit inaccurate, not a massive amount but enough to not look right.
Started changing resistors to make it more accurate but couldnt get it right.
Then realised my pc software uses 4 divisions in the Y direction while voltage into a2d is 3.3. I had forgotten to scale pcb screen to reflect this.
On the last project I changed the screen layout to become a percentage of the pc screen Window. It was when this was done I forgot to scale the screen.
This scope is working well now.
Sadly the AD9220 is getting hard to find and expensive.
So moved onto ADF876JR which more available and cheaper.
Its also twice as fast.
I also have another USB scope in the pipeline, it uses a 300MHZ PIC micro and a 100 meg sampling rate A2D.
Sadly the AD9220 is getting hard to find and expensive.
So moved onto ADF876JR which more available and cheaper.
Its also twice as fast.
I also have another USB scope in the pipeline, it uses a 300MHZ PIC micro and a 100 meg sampling rate A2D.
I meant some standard interface you use, not that you should adapt it to another one.
If it has all the controls and they are pretty intuitive that’s fine!
Didn’t see what the menu options were...
If it has all the controls and they are pretty intuitive that’s fine!
Didn’t see what the menu options were...
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Yes the functions are buried in menu's or mouse right click context menu.
It has trigger functions, time base functions and voltage functions.
There is FFT enable/disable.
You can save bitmaps of screen, save trace to a file or print out a trace.
It has trigger functions, time base functions and voltage functions.
There is FFT enable/disable.
You can save bitmaps of screen, save trace to a file or print out a trace.