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Rasperry Pi as the brains of a programmable keyboard?

e14 Contributor

I'm currently trying to develop a custom computer keyboard and am toying with the idea of using a RPi as the brains of the operation.  This would allow me to do a lot of the custom key commands and macros I'm hoping to build into the keyboard, but I'm not sure of the capabilities of RPi in this application.  Specifically:

 

1. Could RPi be plugged into a full-blown computer and be viewed as a keyboard?

2. Could RPi take inputs from the actual switches by itself or would it need another (presumably usb) device to do this?

 

Any other thoughts would be really appreciated.

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    Michael Bell wrote:

     

    1. Could RPi be plugged into a full-blown computer and be viewed as a keyboard?

    2. Could RPi take inputs from the actual switches by itself or would it need another (presumably usb) device to do this?

    1.  I believe the answer is NO.  RasPi does not have a USB device port so it cannot behave as a USB device.  You could attach a small microcontroller with a USB device port and have RasPi talk to it over I2C or SPI or UART.

     

    RasPi Model B has three USB connectors.  Two are full-size USB A ports connected to the Model B's LAN9512 USB hub/Ethernet chip.  They are downstream ports, so they can be connected to external devices like keyboards, mice, and to the upstream B port of external USB hubs.  However, they cannot be connected to a PC's USB A port.  Model A has just one full-size USB A port, which talks to an external USB device or the upstream B port of an external USB hub.

     

    RasPi also has a Micro USB jack, but it's only for power.  The data pins are unconnected.

     

    2.  I think the way USB keyboards work is that they tell the host about every key transition, up or down.  The keys are encoded by position.  The host's keyboard driver converts the key codes into ASCII characters along with special codes for things like arrow keys and non-ASCII Latin-1 characters.  So you can do lots of custom keyboard stuff in PC software without needing an intermediate device.

  • 0 in reply to johnbeetem

    RasPi does not have a USB device port so it cannot behave as a USB device.

    Other similarly priced devices, such as BBB do have this.

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