Hacker News Reader

Comment by berkes | Hacker News Reader

I would expect that PS/2 to USB could be handled on the computer.

I have little experience, but from debugging some early 3D printers on Linux, I've learned that the U in USB really stands for universal: that it'll just pass on serial stuff to/from the OS, drivers or software on the computer to handle.

View on HN

In addition to electronic singalling being completely different, the serial interface used by many 3d printers is not the same as low level serial interface sent over the wire. There is a low level usb protocol for stuff like data packets ,checksums , metadata negotiation, multiple endpoints in single device, basic transfer types(bulk, isochronous, control, interrupt). All common device types and standard drivers including USB to serial, HID, removable storage is built on top of this layer instead of raw serial sent over the wire. That's why you can have stuff like USB hubs which can forward data to and from multiple devices. And also why you can plug in a USB device, and the OS recognize and lookup driver without user manually configuring what device is plugged into which port.

Having done some embedded development, I am pretty sure that those 3D printers had a serial-over-USB converter like the famous FTDI family of chips. Those chips just simulate a plain old RS232 connection over USB.

There are some motherboards that can switch either PS/2 or RS232 signalling onto USB-A connectors, but this is completely non-standard hack mostly seen on some enterprise stuff few years back that seems to have mostly died away.

Not really no, the timing requirements of the USB protocol are very tight and handled by dedicated circuits. The exception is microcontrollers where you can sometimes achieve the timing in software.

Reply on news.ycombinator.com