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Forum Index : Microcontroller and PC projects : MicroMite + 32MX250F128B + ,,,,,,
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| hitsware Guru  Joined: 23/11/2012 Location: United StatesPosts: 535 |
>A standard KB(USB or PS/2)???? Now that you mention it ...... I have 1 of each ... What are the ramifications of either in this context ? ( plugging into the VT100-Mite ) |
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
gotcha ! |
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Grogster Admin Group  Joined: 31/12/2012 Location: New ZealandPosts: 9489 |
I 2nd that, and it is very good advise. Don't know what the voltage tolerance is for KB's, but unregulated 5v plug-pack could be upwards of 9v or so, depending on at what load the pack is supposed to be 5v, so you could fry your KB with one of those, if the low-load voltage is higher then the KB is happy about. Smoke makes things work. When the smoke gets out, it stops! |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9489 |
The Maximite or VT100 terminal is expecting a PS/2 keyboard. Other then the obvious differences in plugs, some KB's are auto-detecting between PS/2 and USB, others are not. What this means, is that SOME KB's will work on either PS/2 or USB with a suitable adaptor, and others will not. A true USB-only KB would not work with the MaxiMite or VT100 terminal, as PS/2 codes and protocols are different from USB HID(Human Interface Device) protocols. Likewise, a true PS/2 keyboard will not work on a USB port with an adaptor. The ramifications are nothing will be damaged, it simply won't work if you use one on the other. EXAMPLE: Plug USB-only KB into VT100 terminal with an adaptor - KB will not work. Plug PS/2 KB into VT100 terminal, and it will work. Plug PS/2 or USB auto-sensing KB into the VT100 terminal with an adaptor, and it will work.(the KB will auto-detect PS/2) Smoke makes things work. When the smoke gets out, it stops! |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
I have been a long time user of Logitech keyboards. I haven't bought one for a while so what I am about to say may not be valid now. Every Logitech keyboard I have bought has been usb and comes with a usb to ps2 adapter. I have been successfully using my keyboards with the mono Maximite with no trouble except the proximity of the connectors on the mono Maximite. I had to chop part of the VGA shell away to allow the keyboard adapter. On a PC the keyboards work with or without the adapter so maybe they have auto sensing for which ever type of socket protocol. If I can find one of these adapters I will put up a photo a bit later. |
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
I've wondered about that. Since a usb to ps2 (or ps2 to usb) adaptor is (it seems) only a passive gizmo, it would seem that the usb 'buss' is based on what used to be ps2 ?????? |
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| BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
I would doubt that conclusion is valid but I'm no expert. I promised a photo of the Logitech usb to ps2 adapters for keyboard and mouse. As you can see one is for KB and other for mouse. In usage I could find no difference. They both worked on the keyboard but that was a while back so my recall may be faulty. 
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| hitsware Guru Joined: 23/11/2012 Location: United StatesPosts: 535 |
These come free with usb keyboards I just ordered some of these |
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| Grogster Admin Group Joined: 31/12/2012 Location: New ZealandPosts: 9489 |
I also am no expert here, but the two are totally different port designs. For example, USB supports different speeds(USB-FAST and USB-SLOW), and uses a differential data pair(D+ and D-), is bi-directional, and can have up to 127 different devices per port with hubs. PS/2 is a set speed, uses a separate data and clock line, is input only, and(normally) only one device can be on one port at any one time. There were those "Dual-device" PS/2 ports that could have a KB or a mouse or both with a splitter cord, but they always seemed to be laptop-only idea - you'd probably never see that on a full-size motherboard. It is coincidence that both PS/2 and USB have 4 wires. USB3 has 9 wires. @ BobD - I will have to see if I can find a Logitech keyboard to try out with my on-going KB problems on the MM. Smoke makes things work. When the smoke gets out, it stops! |
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CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1427 |
Without getting into a lot of detail, and since it is late and I've had a beer fews, I'll give a brief explanation of how this works. With a PS2 only keyboard, the controller logically expects only PS2 signals. The PS2 signals are a clock and a data line. The round PS2 plug is used. A USB only keyboard expects only USB signals - a bidirectional differential data pair. The rectangular USB plug is used. A keyboard that can be USB or PS2 may have a round PS2 plug, or a square USB plug. An adaptor will provide the other type of connection, but it is only a plug shape conversion. The keyboard powers up when you plug it in. Does it know that you plugged it in with or without an adaptor? No. Does it know right away that it is supposed to be PS2 or USB? No. But it doesn't take long for the controller inside to detect USB signalling or PS2 signalling on the two lines if it is there. I've written code on a certain microcontroller that tries a few USB-ish things when it powers up. If it passes, it is then acts like a USB device. If it fails, it becomes a PS2 device. Micromites and Maximites! - Beginning Maximite |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3998 |
The one I have allows any PS/2 mouse or kb. Those devices do NOT know USB is in use. There is a uC in the thing, and that is what knows USB. It's NOT a passive device at all! John |
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| CircuitGizmos Guru Joined: 08/09/2011 Location: United StatesPosts: 1427 |
That is the active adaptor type. I was referencing just the type w/o any type of electronics in it (other than wire). Explaining how those work. It is a USB device that allows PS2 keyboards/mice to connect to the PC. Micromites and Maximites! - Beginning Maximite |
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| JohnS Guru Joined: 18/11/2011 Location: United KingdomPosts: 3998 |
This is also a USB device that allows PS/2 keyboards/mice to connect to the PC. I don't see how a typical user would tell them apart. (Or why it would matter.) They're the same price, too (0.99). (Many USB devices are 0.99 nowadays!) John |
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