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Control using USB

Former Member

I'm looking at a small project that would enable me to control my sit / stand desk from my PC rather than from the controller.

 

The controller on the front of the desk has a number of buttons on it, including an up and down button.  Additionally it has a 3 part 7 segment display that shows the height in inches e.g. 27.8.  I'm going to handle this in two stages:

 

1)     I want to be able to move the desk up / down from my PC over USB

2)     I want to retrieve the value displayed on the 3 part display and then pass it to the PC over USB so that it can be displayed (and used) on the PC.

 

I was looking at the FTDI FT245B chip, is that my best choice?  And if so any suggestions on how to then indigrate it to the two push button switches (Up / Down). 

 

Thanks

 

Andrew

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  • Well, that doesn't sound too complex, the electrical interface is already there you just need to "hack" into it with an MCU.

    Why an MCU rather than than an FT245B?

    • An NZ$13 dev kit (like this one) will provide:
      • An MCU with on-board serial/USB functionality for your choice of PC interface
      • A USB connector with suitable IO circuity (protection)
      • A regulator to allow the device to be USB bus powered
      • Points to solder on GPIO lines to the buttons/Read-Out (maybe with some voltage matching circuits)
      • Handle the interface to the desk position on-board (no extra circuits, except maybe voltage matching).
      • Plenty of room for extra features
      • The example one is pretty easy to code via mbed.org, or an USB capable arduino would be excellent

    The buttons will either be pull-up or pull-down (electrically). So your circuity will need to match that.

    Pull (in code) the button's lines up (or down)  to whatever voltage they need when you want to move the desk in that direction, by using an MCUs GPIO lines.

    As for the Read-Out, the 7 Seg display may be driven from a common driver that takes binary in and outputs the segments. In which case you can parallel those lines into the MCU and read them as 1 or 2 bytes. Otherwise it might be some kind of non-volatile encoder/ potentiometer that helps the desk know its position, if you can break that out to the MCU with an appropriate interface, then the MCU can read the position on its own.

     

    Good Luck

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  • Well, that doesn't sound too complex, the electrical interface is already there you just need to "hack" into it with an MCU.

    Why an MCU rather than than an FT245B?

    • An NZ$13 dev kit (like this one) will provide:
      • An MCU with on-board serial/USB functionality for your choice of PC interface
      • A USB connector with suitable IO circuity (protection)
      • A regulator to allow the device to be USB bus powered
      • Points to solder on GPIO lines to the buttons/Read-Out (maybe with some voltage matching circuits)
      • Handle the interface to the desk position on-board (no extra circuits, except maybe voltage matching).
      • Plenty of room for extra features
      • The example one is pretty easy to code via mbed.org, or an USB capable arduino would be excellent

    The buttons will either be pull-up or pull-down (electrically). So your circuity will need to match that.

    Pull (in code) the button's lines up (or down)  to whatever voltage they need when you want to move the desk in that direction, by using an MCUs GPIO lines.

    As for the Read-Out, the 7 Seg display may be driven from a common driver that takes binary in and outputs the segments. In which case you can parallel those lines into the MCU and read them as 1 or 2 bytes. Otherwise it might be some kind of non-volatile encoder/ potentiometer that helps the desk know its position, if you can break that out to the MCU with an appropriate interface, then the MCU can read the position on its own.

     

    Good Luck

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