Using a wired keyboard - pitfall


6 posts
by colin B » Sat Apr 28, 2012 6:16 am
I decided to try my wired keyboard with the Pi and found that the keyboard would not work when plugged into my powered USB hub (though the mouse does) and on the Raspberry Pi itself it needs to be plugged into the lower USB port (which is the main port).

The keyboard is recognised but won't work at all if plugged into the top port and the Pi will just keep rebooting.

Keyboard is an HP brand and is recognised as a 'Chicano keyboard'.
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by Techmeology » Sat Apr 28, 2012 2:02 pm
Some powered hubs have been known to cause problems (http://elinux.org/RPi_Verified.....d_USB_Hubs). It sounds to me as if your Pi doesn't have enough power for the keyboard when you plug it in directly. What power supply are you using and what voltage/current rating is it?
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by rew » Sat Apr 28, 2012 6:40 pm
Some keyboards trip the fuse for 100mA as well.

My keyboard, a cheap Logitech one uses about 20mA, and is fine.
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by colin B » Sat Apr 28, 2012 8:52 pm
I don't think power is a problem, as the hub is powered, the mouse uses more current than the keyboard and if the keyboard is inserted into slot 0 of the USB (the lower one) port it works.

Slot 0 goes connects directly to the  SOC via the protection fuses whereas slot 1 connects to the LAN9512 chip.
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by Chris.Rowland » Sat Apr 28, 2012 9:39 pm
bodgyuk said:


Slot 0 goes connects directly to the  SOC via the protection fuses whereas slot 1 connects to the LAN9512 chip.


Are you sure? My reading of the circuit is that for model B the direct connections to the lower USB socket, R36 and R37, are not present and the connection goes through LAN 9512 which supplies the two USB sockets and the Ethernet.

On Model A R36 and R37 are present but LAN9512 is not.
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by colin B » Sat Apr 28, 2012 9:52 pm

Chris Rowland said:

Are you sure?

On Model A R36 and R37 are present but LAN9512 is not.


My error, you are correct. I'll have to dig further, but the keyboard definitely doesn't work in the top slot. I'll try someother USB devices in the top slot to see if there is a port problem.
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