Just purchased a Open-source Oscilloscope DIY kit DSO138, with surface mount components soldered. Here how I assembled it in 2 hours.
After assembled, check voltage on TP22. Make sure it is arround 3.3V. Then short JP4 and install LCD module.
Notice: This video recorded after my final tested, so JP4 have been shorted at beginning. Actually, you have to keep it open after 3.3V on TP22 confirmed.
After the kit worked, align the 0V line and calibrate the probe.
For details and update of the DSO 138 DIY Kit, read Users Manual on the website.
Tested with Arduino Due generated sin wave.