I have't been able to find a solution, and was hoping for some clarity. I have 2 machines (one is a bill counter, one is a coin sorter) that both support printing over DB9 serial connection, and one printer that has a 25 pin input.
The goal is to have the single printer handle printing for both units through a y-split. On the bill counter in this setup, I am able to print from the bill counter with minor data corruption (a few odd characters interspersed), but am unable to print anything from the coin sorter. Either singulated unit plugged into the Y cable works independently with the other unit not plugged in, the cable integrity and pinouts seems fine. For both units, in theory, they should only be communicating with the printer when a manual print request is initiated, but I do not have access to either protocol manual, or port testing equipment, just a standard DMM.
Do I need to filter each comm line with diodes? Any insight as to why the other unit wouldn't print when both devices are attached?
Please let me know your thoughts or what additional information I may provide to help drive finding a solution.