PS/2 keyboard and PS/2 mouse with USB converter not working?


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by wyattwong » Mon Mar 18, 2013 2:57 pm
I have a PS/2 keyboard and PS/2 mouse and use a 2-in-1 PS/2 to USB converter to connect to Raspberry Pi but I found that Raspbian “wheezy” Linux cannot detect the keyboard (and probably also mouse). I can only see the Num-Lock, Caps-Lock and Function-Lock lights flash for a short while when I plug in the USB.

I have also attach a USB receiver for a wireless keyboard and mouse to Raspberry Pi but the USB receiver did not show any lights.
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by FTrevorGowen » Mon Mar 18, 2013 5:36 pm
Some PS/2 to USB adapters require a powered hub to work (they may draw upto 500mA). What does "lsusb" and "usb-devices" report for yours? The few examples I've tried can be seen at http://www.cpmspectrepi.webspace.virgin ... pters.html . For more info. on keyboard, mice and other "Pi compatible" devices see http://elinux.org/RPi_VerifiedPeripherals.
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Mainly running "Wheezy Raspbian" on seven Pi's (an A, B1, 2xB2, 2xB+ and an A+). Notes about them begin at http://www.cpmspectrepi.webspace.virginmedia.com/raspberry_pi/raspiidx.htm
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by pij » Sun Mar 31, 2013 11:06 am
i can confirm that this is a *new* problem with raspbian 2013-02-09

raspbian 2012-12-16 works fine with two different usb-to-ps2 keyboard/mouse adapters, with and without a hub

to confirm this, do a fresh boot with raspbian 2012-12-16 and your ps2 keyboard connected via the adapter. you can use the keyboard just fine in the first-boot setup menu program.

raspbian 2013-02-09 does not
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by pij » Sun Mar 31, 2013 5:49 pm
(replying to myself after further digging because i need this to work on latest raspbians)

did a number of fresh-imaging of raspbian and booting with various wiring combinations ... turns out all versions sometimes work and sometimes don't, though the 2013 version seems to work less often. it depends how is wired:


what *always* works:

power the raspberry pi with a usb cable with plenty of power - some of the cell phone adapters do not seem have enough power.. try powering it from a computer usb port just to make sure it works .. they seem to have enough power


what does not always work:

* lower-powered usb converters (e.g. cell phone or bluetooth chargers)

* the powered usb hub powers the raspberry pi. yes i mean the usb hub connecting to the power of the pi, and *also* one of its usb outputs, and then the keyboard/mouse adapter into the hub. this sometimes works on the older raspbians. maybe i need a higher-output powered usb hub. though it seems like a usb loop, i am assuming the raspberry power only caries power not data. anyhow this works sometimes.


in other words, "is it plugged in? properly?"
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by mahjongg » Sun Mar 31, 2013 7:51 pm
real PS/2 devices are 5V +-5% devices, (they need a 4.75 to 5.25V supply) while real USB (100mA) devices are designed to work with voltages as low as 4.0V. This means that PS/2 devices with an USB adapter are much more susceptible to power supply losses than real USB keyboards (and mice).

this fact has been already mentioned in the WIKI for a long time.

the problem is compounded by the fact that there are real USB keyboards that can also function as a PS/2 keyboard by use of (not using) a passive connector adapter. Such an adapter looks like an active USB adapter (containing an USB chip), but in fact only contain wires.
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