Well the other possibility is to use the ADC inputs and record the signal data.
I have an EVK1100 Development board with 32MB ram and 8 ADC inputs. It has over 100 IO pins as well, that’s why I was going to go with simple logic input rather than ADCs, that way I can record a good 30 seconds or so of data, from every contact on the ribbon cable, to the ram then send it to the computer through the uart.
Once we have the data I can use a scope on each contact to determine the driving voltage, if you haven’t already done so.
I’m well aware of the t-shirt printer projects around using the original printer controller but I want to work directly with the print head more for experimenting and curiosity. Also because there are many more projects that could use a decent print head driven directly from a MCU