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?