I have ~26 parallel inputs that I would like serialize and send to a computer over USB. I decided to chain together 4 LS165 parallel-in serial-out shift registers, but I don't know how I would send this serial signal over USB. I considered using an FTDI FT232RL, but I'm not sure how I would make my serial signal into UART. I would like to avoid using a microcontroller in the middle if possible, but I will if it will make my life easier. Is there a simple way to take this basic serial stream and send it over USB?
A relatively straightforward problem:
Create a small state machine to drive your parallel capture, serial clock and character serializer. This is very easy with a small ROM/EEPROM and a couple of multiplexers.
Transfer 3 bits at a time into another 4 * LS165 configured as a 3 character serializer. Configure the three characters as 'group' (char 'A' to 'I'), 'Value' (char '0' to '8'), CR (chare carriage return).
Create a baud rate generator to transfer your characters from the serializer and provide a clock for the state machine.
Clock the serial data into an FT232H configured as a UART to provide your serial to USB conversion.
For extra points, receive a serial command from the PC to start and stop your serializer.
All up about 15+ chips, but easy to layout.
Use something like an Arduino Nano for about $4 (including USB connectors and cable) and write a few lines of code to transfer the data. You could even use the newer Arduino Micro based on the ATMega32u4 and get a single chip solution with USB connectivity for about the same price.