Asus USB/MIR reverse engineering

Robhalfordfan wrote on 2023-07-08, 13:50:

Hello all […]
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Hello all

i Have an Asus P5A-B Motherboard and noticed it can use Asus usb/mir breakout card

i can find this card (with usb only) online quite easily

i was wondering is it difficult to add ps/2 port and irda port on the card itself (voltages, resisters etc) and make or alter a ribbon cable for it as i can't seem to find one with everything on it and the ribbon cable needed to connect to mobo

At a glance, it looks like the missing capacitors and inductances would constitute low pass filters for signal conditioning. Don't take my word for it since I only have photos as reference - double check connections etc yourself - but I'd bet you would get away with simply bridging the solder pads for the inductances L2 and L3, leaving the pads for the caps (C*) open. If the low speed PS/2 interface actually is sensitive to EMI and the filters are vital, it's easy enough to reverse. As for the IRDA interface, you probably just need the connector, and can omit the decoupling caps.

Mini DIN connectors can be sourced on Ebay, Aliexpress, etc, or with some luck, your local electronics store. Make sure to get connectors for the card's hole pattern, there might be variants.

Pressing IDC connectors is easy, no special tools needed. I've done it numerous times in a regular vise with perfect results. It would probably work to carefully tap the connector together with a hammer too.
18 way IDC connectors and ribbon cable can be sourced from Ebay etc. aswell. You could butcher an old IDE or FDD cable if you want to save a few bucks on the ribbon cable.

Edit: Indeed, those USB only cards are easy to find. Ordered one for my P5A-B mobo that's missing it, should be here within a week or two. I'll test my theory on it and revert here once it's done, if I remember to 😀

Only connections are needed: four inductors, and they are low ohm will do, and very small value around pf range for capacitors on all 4 signal lines, two each for keyboard and mouse ports.

Easy to do. The header and ribbon cable can be made and sourced.

Cheers,

I've done this exact thing. Ordered one of those boards and added PS2 for mouse. Worked easily. Just added the headers and bridged the required points, didn't need any other components, though I expect if you want IR too, they'll be needed.

thank you to everyone for advice and helping and maybe a small future project 😁

hopefully hear back from kaputnik and see how his theory goes 😁

Robhalfordfan wrote on 2023-07-10, 22:25:

thank you to everyone for advice and helping and maybe a small future project 😁

hopefully hear back from kaputnik and see how his theory goes 😁

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way to test it 😀

- Prepared the board by removing solder from the holes that were going to be populated. Used regular solder wick and some additional flux.
- Bridged the L2 and L3 solder pads, taking care to avoid bridging the capacitor pads etc accidentally .
- Installed a fuse on the shared 5VDC line. Only had a 3.15A one that fit mechanically, it'll at least give some kind of protection as opposed to a bridge. Gonna get a lower rated one in a more compact form factor at some point. 315 or 500 mA should do, since I don't need IR.
- Populated the remaining part of the connection header.
- Installed a Mini DIN connector.
- Drilled a 10mm hole in the bracket for the new connector. Clamped it to a piece of wood and used a step drill.
- Scrounged up a 20 way flat cable from my stashes, my local electronics supplier didn't have 18 pin IDC connectors anyways. There's room for the somewhat larger connectors in both ends, nothing on the boards colliding with them. Plugged the holes corresponding to the missing pin 14 in the headers for keying. Took a small piece of plastic and melted it in with the soldering iron set to 200 deg C. Got an old tip I don't care about for that kind of jobs.
- Verified that everything was connected correctly, that there were no unintentional shorts, etc. The header pinout is in the P5A-B manual.

If I'm to guess, the filtering is mostly for regulation compliance, and not really needed for the interfaces to work properly.

kaputnik wrote on 2023-07-15, 18:18:

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way t […]
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Robhalfordfan wrote on 2023-07-10, 22:25:

thank you to everyone for advice and helping and maybe a small future project 😁

hopefully hear back from kaputnik and see how his theory goes 😁

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way to test it 😀

- Prepared the board by removing solder from the holes that were going to be populated. Used regular solder wick and some additional flux.
- Bridged the L2 and L3 solder pads, taking care to avoid bridging the capacitor pads etc accidentally .
- Installed a fuse on the shared 5VDC line. Only had a 3.15A one that fit mechanically, it'll at least give some kind of protection as opposed to a bridge. Gonna get a lower rated one in a more compact form factor at some point. 315 or 500 mA should do, since I don't need IR.
- Populated the remaining part of the connection header.
- Installed a Mini DIN connector.
- Drilled a 10mm hole in the bracket for the new connector. Clamped it to a piece of wood and used a step drill.
- Scrounged up a 20 way flat cable from my stashes, my local electronics supplier didn't have 18 pin IDC connectors anyways. There's room for the somewhat larger connectors in both ends, nothing on the boards colliding with them. Plugged the holes corresponding to the missing pin 14 in the headers for keying. Took a small piece of plastic and melted it in with the soldering iron set to 200 deg C. Got an old tip I don't care about for that kind of jobs.
- Verified that everything was connected correctly, that there were no unintentional shorts, etc. The header pinout is in the P5A-B manual.

If I'm to guess, the filtering is mostly for regulation compliance, and not really needed for the interfaces to work properly.

1.jpg
2.jpg
3.jpg

That's excelleant to see and hear and hopefully be able to dodthis myself since i only have really basic soldering skills but how do we learn and get better by doing it and nothing ventured, nothing gained

Robhalfordfan wrote on 2023-07-20, 13:02:

kaputnik wrote on 2023-07-15, 18:18:

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way t […]
Show full quote

Robhalfordfan wrote on 2023-07-10, 22:25:

thank you to everyone for advice and helping and maybe a small future project 😁

hopefully hear back from kaputnik and see how his theory goes 😁

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way to test it 😀

- Prepared the board by removing solder from the holes that were going to be populated. Used regular solder wick and some additional flux.
- Bridged the L2 and L3 solder pads, taking care to avoid bridging the capacitor pads etc accidentally .
- Installed a fuse on the shared 5VDC line. Only had a 3.15A one that fit mechanically, it'll at least give some kind of protection as opposed to a bridge. Gonna get a lower rated one in a more compact form factor at some point. 315 or 500 mA should do, since I don't need IR.
- Populated the remaining part of the connection header.
- Installed a Mini DIN connector.
- Drilled a 10mm hole in the bracket for the new connector. Clamped it to a piece of wood and used a step drill.
- Scrounged up a 20 way flat cable from my stashes, my local electronics supplier didn't have 18 pin IDC connectors anyways. There's room for the somewhat larger connectors in both ends, nothing on the boards colliding with them. Plugged the holes corresponding to the missing pin 14 in the headers for keying. Took a small piece of plastic and melted it in with the soldering iron set to 200 deg C. Got an old tip I don't care about for that kind of jobs.
- Verified that everything was connected correctly, that there were no unintentional shorts, etc. The header pinout is in the P5A-B manual.

If I'm to guess, the filtering is mostly for regulation compliance, and not really needed for the interfaces to work properly.

1.jpg
2.jpg
3.jpg

That's excelleant to see and hear and hopefully be able to dodthis myself since i only have really basic soldering skills but how do we learn and get better by doing it and nothing ventured, nothing gained

The soldering is very basic, a perfect newbie project if you ask me. You'll figure it out for sure, just be careful and take your time. And yes, no one remembers a coward 😁

kaputnik wrote on 2023-07-22, 16:03:

Robhalfordfan wrote on 2023-07-20, 13:02:

kaputnik wrote on 2023-07-15, 18:18:

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way t […]
Show full quote

Got the USB/MIR 1.11 board and modded it. As expected, it works perfectly. Only did PS/2 since I got no use for IR, and no way to test it 😀

- Prepared the board by removing solder from the holes that were going to be populated. Used regular solder wick and some additional flux.
- Bridged the L2 and L3 solder pads, taking care to avoid bridging the capacitor pads etc accidentally .
- Installed a fuse on the shared 5VDC line. Only had a 3.15A one that fit mechanically, it'll at least give some kind of protection as opposed to a bridge. Gonna get a lower rated one in a more compact form factor at some point. 315 or 500 mA should do, since I don't need IR.
- Populated the remaining part of the connection header.
- Installed a Mini DIN connector.
- Drilled a 10mm hole in the bracket for the new connector. Clamped it to a piece of wood and used a step drill.
- Scrounged up a 20 way flat cable from my stashes, my local electronics supplier didn't have 18 pin IDC connectors anyways. There's room for the somewhat larger connectors in both ends, nothing on the boards colliding with them. Plugged the holes corresponding to the missing pin 14 in the headers for keying. Took a small piece of plastic and melted it in with the soldering iron set to 200 deg C. Got an old tip I don't care about for that kind of jobs.
- Verified that everything was connected correctly, that there were no unintentional shorts, etc. The header pinout is in the P5A-B manual.

If I'm to guess, the filtering is mostly for regulation compliance, and not really needed for the interfaces to work properly.

1.jpg
2.jpg
3.jpg

That's excelleant to see and hear and hopefully be able to dodthis myself since i only have really basic soldering skills but how do we learn and get better by doing it and nothing ventured, nothing gained

The soldering is very basic, a perfect newbie project if you ask me. You'll figure it out for sure, just be careful and take your time. And yes, no one remembers a coward 😁

I will figure it out and give it a go 😀