DIY Raspberry Pi Oscilloscope
As a follow-up to the toy oscilloscope I designed here, I designed and built something that more closely resembles a real oscilloscope! I included some shots of the build process, all done at home by hand with a hot air station and a preheater.
It has 2 channels, each running an ADC3908 off of a shared clock at anywhere from 1MS/s to 62.5MS/s. I wanted to use the 125MS/s version of the part but since I'm still using the Pi for all of the data acquisition and processing, this is about as fast as you can possibly go.
The front-end was supposed to have ~30MHz of analog bandwidth but since I had to remove the filter caps after assembly, I think theoretically it has whatever the bandwidth is at the ADC inputs. All of the analog components before the ADC have higher bandwidth.
It supports input full-scale ranges from +/-33mV to +/-180V, though I'm hesitant to plug something I made into mains power. It should be isolated as all power comes from the Pi, either through a wall plug or USB powerbank, but I'm still wary. I'll probably try it one day though.
It wound up costing way more than I would have hoped, and I probably chose some components that were more expensive than necessary. For example: the two linear regulators I used for the analog supply rails are pricy because of their very low noise, but my actual noise levels aren't great in the end. I think the total BOM cost was ~$150 if you include the PCB and you can get a way faster real scope for that price. It was still a great learning project though.
