Ratings & Rabbit Holes

The Slippery Slope

So I say “sayonara” to the Arduino, pull up EAGLE (a program that deserves a longish rant all on its own), and start tinkering.  I’m still thinking simple here; just some USB-connected buttons and lights.  Nothing fancy.

For a processor, being a PIC guy, I settle on the PIC18F4550.  It’s a larger device that can run at up to 48MHz, and has 32K flash, 2K SRAM, and 256 bytes of EEPROM.  Add to that a raft of useful peripherals including PWM and, of course, the necessary internal USB SIE and transceiver.  Available in 40-DIP or 44-TQFP.

Hint:  Buy them direct from Microchip if you need more than one.  They sell ’em for $4.47, where Digi-Key’s price is $6.80.  SparkFun’s price is a whopping $11.39.  Ouch!

With the processor chosen, I next learn that the road to hell is paved with lighted pushbuttons.

The stupid things are expensive!  I’m not talking three or four bucks here – more like ten for the good ones.  I spent hours looking all over the place, but apart from finding some at Adafruit that weren’t quite right for the project, I found absolutely nothing that was reasonably priced.  I must be missing something…

In the end I settled on some E-Switch LP4’s.  They’re a bit small, but they’re (mostly) under five bucks, and they’ll work.  Even better, they have a removable clear cap that I can put an insert under, and the caps are designed so they don’t twist – get your insert aligned properly, and it’ll stay that way.

No tactile feedback and still more than a bit too pricey, but you can’t have it all I suppose.

Of course, by the time I get all this together, I’ve noticed just how many extra pins I’ll have on my fancy new MCU…

… and that’s how it always starts …

Down The Rabbit Hole

So there I am, staring at all those lovely I/O pins just begging me to find a use for them.  Having had the Arduino prototype sitting on my desk for a while, I’ve already figured out that having some basic controls wouldn’t be a bad thing.  So the design grows three more buttons:  next track, previous track, and play/pause.

Well, that’s reasonable, but I’ve still got tons of extra pins.  Why not turn it into a hardware iTunes control and status panel?  Not that hard, right?  Of course, there’s a pretty standard way of doing that…

…add an LCD display, of course.

I happen to have some in the parts bin from a project I lost interest in a long time ago, so that wasn’t a tough choice.  They’re fairly nice 16×2 units I bought from CrystalFontz.  Ten years old they may be, but they work just fine, and have a traditional Hitachi-compatible controller.  It’s amazing how little things have changed over the years; these things are still just as popular, if not more so.

Of course, while I’m tinkering with adding that to the schematic, I realize that I’ll have to hardwire the contrast or add a user-accessible potentiometer to set it with.  This leads to thoughts of software controllable display parameters, and next thing I know, one of the PIC’s PWM modules is consumed with powering the backlight.  Haven’t decided yet how to deal with contrast, but I’ll figure something out.

So in the end I have nine buttons, six of which have LEDs in them, and an LCD display.  The MCU is clocked by an 8MHz crystal, which drives an internal 3x PLL for a system clock of 24MHz.

But will it blend?

About Steve

When it comes to the desktop, Steve is a former Amiga, Windows, and Linux user, and as of six years ago, a die-hard Mac head (who, for once, isn't thinking of changing platforms again any time soon). When it comes to the server, Linux is pretty much the only game he plays. He also enjoys hardware hacking, and shouldn't be allowed near a keyboard after the sun sets (or for that matter, after it rises. Don't say I didn't warn you).
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8 Responses to Ratings & Rabbit Holes

  1. Pingback: Overbuilding an iTunes rating system - Hack a Day

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  5. Akhil P says:

    nice post

  6. Pingback: Overbuilding an iTunes rating system | CisforComputers

  7. Pingback: Overbuilding an iTunes rating system » Geko Geek

  8. Matthew Wiebe says:

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    I hate being sent to some stupid image-sharing service to see the full size…. Ten clicks later…. Oh.. I’m not interested any more..!

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