MiSTer FPGA Forum

If I plug the serial User port on the standard IO board (which resembles USB) into a USB switcher, and run two male-to-female USB cables from the switcher to two different positions, will this give me two discrete USB ports that I can designate as the one which has serial access depending on how I flip the switch?

Reason I ask:
I am in the process of building out a custom MiSTer case that I've wired up to be operational from the outside. I intend to mount a SNAC adapter on the inside of the case, behind a cutout in the exterior panel intended to allow a user to slot in SNAC controller adapters with 3D printed housings as modular ports that sit flush with the case exterior. (Thus giving you the feel of plugging your retro controller directly into the machine.)

If possible I would like to also preserve generic serial access from the outside, and if running the serial port through a switcher works I intend to mount the modular SNAC port at the front of the case, while mounting a generic-looking USB port at the back of the case labeled "Serial" with a thumb switch above it. I'd then wire the thumbswitch to the USB switcher inside the case so the user can simply reach around back, flip a switch, plug in a USB cable, and gain generic serial access.

I'm not aware of such a switcher. You'd need something that is basically entirely passive or otherwise just routes a signal without expecting it to be USB. Nearly anything of this type would be expecting a USB signal, and that would likely do some damage to either the switcher or MiSTer.

Like an old-school data switch would work. These are usually completely passive. However, two issues.

1. You'd need either an io board that uses a db9 serial connector instead of usb3; or you'd need to make a usb to db9 adapter.
2. This would increase the over cable length travel between mister and user port device, which can cause issues (MT32-PI)

Device in question: https://www.monoprice.com/product?p_id=39282

I've actually thought of testing this out. I'm wondering if a smaller board with switch built in could be designed to plug directly into the user port. I have some idea about this but don't have the experience (yet) to implement it.

I would be very hesitant to do this for the same reasons jdeberhart just stated. If there is a USB controller and extra circuitry in whatever usb switch you use, it could damage your hardware.

I agree most usb splitters/switchers will have active components and would likely damage the MiSTer or IO Board. However, old school manual data switches have no active electronics installed and mechanically move connections to complete a circuit, which is roughly equivalent to completely unplugging one connection, then plugging in a new one.

I would still suggest powering off the mister between switching, but this would (in theory) at least allow you to have all devices constantly 'plugged in'. Looking specifically for 'manual data switches', and trying to find something smaller with shorter cable runs I came across this:

https://www.amazon.com/dp/B074FT6YG1/

I wish I could produce a switch box, such as the ones being marketed in the '80s used to share 1 (serial) printer among multiple computers.

The idea interests me mostly

jdeberhart wrote: ↑Mon Aug 09, 2021 9:49 pm I'm not aware of such a switcher. You'd need something that is basically entirely passive or otherwise just routes a signal without expecting it to be USB. Nearly anything of this type would be expecting a USB signal, and that would likely do some damage to either the switcher or MiSTer.

aberu wrote: ↑Tue Aug 10, 2021 12:49 am I would be very hesitant to do this for the same reasons jdeberhart just stated. If there is a USB controller and extra circuitry in whatever usb switch you use, it could damage your hardware.

cmstar0 wrote: ↑Tue Aug 10, 2021 2:22 am I agree most usb splitters/switchers will have active components and would likely damage the MiSTer or IO Board.

Yeah, the potential of damage seems to be a common theme here, and I appreciate all the warnings. I am unlikely to pursue using a switch for this reason.

cmstar0 wrote: ↑Tue Aug 10, 2021 12:13 am Like an old-school data switch would work. These are usually completely passive. However, two issues.

1. You'd need either an io board that uses a db9 serial connector instead of usb3; or you'd need to make a usb to db9 adapter.
2. This would increase the over cable length travel between mister and user port device, which can cause issues (MT32-PI)

Device in question: https://www.monoprice.com/product?p_id=39282

I've actually thought of testing this out. I'm wondering if a smaller board with switch built in could be designed to plug directly into the user port. I have some idea about this but don't have the experience (yet) to implement it.

cmstar0 wrote: ↑Tue Aug 10, 2021 2:22 am However, old school manual data switches have no active electronics installed and mechanically move connections to complete a circuit, which is roughly equivalent to completely unplugging one connection, then plugging in a new one.

I would still suggest powering off the mister between switching, but this would (in theory) at least allow you to have all devices constantly 'plugged in'. Looking specifically for 'manual data switches', and trying to find something smaller with shorter cable runs I came across this:

https://www.amazon.com/dp/B074FT6YG1/

I was looking at very similar boxes when first contemplating the implementation of a switch. My plan (as cmstar suggests) was to make a usb to db9 adapter and use an old mechanical switcher to do the actual handover. Then I realized I wasn't actually sure *how* the serial over USB implementation works and figured I should ask if I could just use a regular old USB switcher. Ultimately, the potential for damage and issues you raise with cable length and powercylcing the unit have dissuaded me from the idea. However, I feel I've solved my dilemma with a better alternate solution: I've modified my design for the 3D printed housings, such that a typical USB extender running from the serial port is mounted behind the cutout in the exterior panel, then a longer shafted adapter housing which holds the SNAC is inserted, and a SNAC controller adapter is inserted after that, leaving the front of the second housing flush with the exterior of the case. I've modeled little tabs for the controller adapters to be easy to swap in and out without removing the SNAC housing. For true serial access, the user can remove both modular "pop-ins" (for lack of a better term) and insert a usb cable into the extender mounted at the back of the cutout.

lamarax wrote: ↑Tue Aug 10, 2021 7:56 pm I wish I could produce a switch box, such as the ones being marketed in the '80s used to share 1 (serial) printer among multiple computers.

Two seem to have been linked as assembled products available for sale in the above thread - unless you meant for the sake of learning how to do it yourself, in which case I salute you but have roughly zero knowledge of mechanical serial switchers from the 1980s myself.