Brad Fitzpatrick (brad) wrote,
Brad Fitzpatrick

breadboard UARTs. Help?

I want to build a grid of christmas lights for the roof of my house where I can control each light (pixel) independently, and do a big video wall type thing.

My dad proposed a grid with shift elements along two edges.

Somehow I need to interface to a serial/parallel port and send along a few commands:

Shift 1 left
Shift 0 left
Shift 1 up
Shift 0 up
Light on
Light off

And hell, as long as I'm being lazy and fitting the commands into a byte, got plenty of room for other commands... maybe dimming commands to vary the voltage and fade things in and out?

If my display is 14 feet by 10 feet tall, and I do one pixel per 3" square, that's a resolution of 56 x 40.... I just brought that up in gimp and it's plenty of space to work with to do cheesy christmas animations.

Okay, so to refresh the display it'd take 1 + 56 + 40 + 1 = 98 commands... off, program horizontal, program vertical, on. 98 bytes (lazy encoding) = 882 bits, or 992 bits with a serial port adding a stop bit in 8-N-1 mode. With a 57.6kbps serial line I could do 60 fps, but that's overkill.... I'd hit problems with the lights fading out too slowly.

So, the real question: how do I interface hardware with a serial line? Can I buy a UART chip with a simple interface? What I think I need is some chip that gives me 9 pins: 8 data bits, and a "new byte ready" pin.

Help? (I'm such a LiveJournal question whore.)

I found these MAX RS232 parts. Maybe what I need?

  • Post a new comment


    default userpic

    Your reply will be screened

    Your IP address will be recorded 

    When you submit the form an invisible reCAPTCHA check will be performed.
    You must follow the Privacy Policy and Google Terms of use.