I haven’t posted in a long time. For one thing, work has been busy. Also I have been making progress here and there in a number of ways, none of which directly merit an article. My solution is to briefly sum up all of my progress here.
Renaming the Project
Up to this point the project as been called “CRT Ocilloscope LCD Mod” or “Oscilloscope Mod” which is a bad name because a) It’s primarily a logic analyser with an Oscilloscope option b) It doesn’t actually describe the project. I have now chosen to call the project HP2VGA.
The last article showed that I decoded a frame in matlab. This has developed and I now have the FPGA in the loop, converting frames in real time to VGA and driving the display. This is currently handled by the Digilent Nexys 4 DDR board which has a massive Xilinx FPGA on it. This will be replaced by my own board with a smaller, cheaper FPGA.
Due to the requirements of the FPGA, I’ve had to use a 0.8mm BGA package which means I’ve had to move to a four layer board – this will be my first four layer board for a personal project and my first BGA design. Overall I think my design has worked out quite nicely at under 4 square inches.
Driving VGA Signal
I have settled on the ADV7125 as my VGA driver of choice. It has 24-bit RGB output which is probably overkill but will allow me to do grey-scale to RGB conversion if I get round to it.
Removing the CRT
The HP1662AS has a Cathode Ray Tube display that need removing (I also want to use it in a future project). It was a pain to get to, but at least there was a service manual. After removing almost every component from the body I was able to get to the one torque bolt and three 7mm hex-nuts (which required a me to buy a set of box spanners!).
Mounting New Hardware
The new display actually fits pretty nicely, however the display isn’t quite the right aspect ratio so I am going to have to 3D print some parts to cover this up.
I will also print parts to mount the new PCB in the HP1662AS.