Nerdy Texts of Analog and Embedded Systems Wizardry

It was with great pleasure that I posted the initial list of hardware features that will make it into the next hardware revision of WTPA on the Narrat1ve forum. Until you start seeing boards rolling out, there’s still time to change this stuff, so feel free to let me know what you think and what you’d like to see.

Here they are, as well as what they do for the kit and what they’ll do to the price:
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1.) WTPA 2 will have 8 controller buttons and not six (the very first one had 5 I think). This will allow us to avoid the dreaded 3-button combo when accessing functions. However, this means two more buttons, and one more shift register IC and socket. This costs more.

2.) There will be a through hole RAM chip. This means the whole kit will be through hole (no smt). This will probably cost about the same, but the board will need to get a little bigger.

3.) The analog sample clock will be based on a 4046 and not an op-amp relaxation oscillator. I can do this because I don’t need the extra op-amp section for overdubbing. This will cost a little less and will also allow CV input to the clock.

4.) The control pot will be replaced with an endless rotary encoder. This will help in all kinds of subtle ways. This may cost a hair more. Given enough pins, I may add a second encoder.

5.) The MCU will be either an Atmega644p or 324p, simply because I want the freedom to add new functions and we’re pretty much out of flash memory on the 164. This will also give us more RAM which may help some of the granularizing functions, and may be able to help with ISR speed if I’m smart about buffering. Those chips are still a 40-pin dip. They cost more.

6.) Some of the values in the analog section will change, which will result in slightly more headroom. This will probably cost about the same.

7.) The bus which is just hanging out doing nothing on the v1 WTPA will be used to access permanent memory. There will be an optional daughterboard which will contain a flash memory chip and will be able to store either 8, 16, or 32 samples depending on how some pricing and availability works out for me. I _might_ implement a sample loader via MIDI. Maybe. The daughterboard will come assembled (all that stuff is small smt biz) and will cost more than $20. Not sure how much more. So permanent storage will be optional.

8.) Instead of a hardware goodie bag, there will be another optional board which will have PCB mounted jacks for MIDI, Audio, and DC. Second to the RAM chip, most build problems in V1 were in the wiring. This should eliminate that problem. This board will mount under the main board. This will _probably_ be more expensive than the goodie bag, but may not be depending on some of the jack pricing.

9.) The routing from the input amp to the AVR will change A LOT. This should lower the noise floor a little.

10.) Because of all these changes, the board will be bigger. Probably not a lot bigger, though. My guess is the price will go up a little too.

OK. I finished shoe-horning necessary functions into this beast. Somebody tell me something that needs to change or this beta becomes legit by tomorrow.
There are a whopping 12 bytes left in memory, and the OS has had a lot of fat trimmed.

Here’s beta 4 (final):
http://www.narrat1ve.com/WTPA_Firmware_0x03.tar.gz

And here’s the R3 changelog, so if you don’t know, now you know:

Firmware Version 0x03:
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Wed Sep 2 09:37:49 CDT 2009

Done:
— Hardcoded explicit bank start address variables into define statements. They are constants in our current system; this will prevent them from being overwritten, save us some RAM and some cycles.
— Sample Start / Window / Endpoint editing, realtime adjustment. Samples with will reverse when the start point is put after the endpoint.
— Separated the “bail” command for FX and loop adjustments in MIDI
— Re-number MIDI CCs
— Added MIDI option to edit samples with wide range or tighter resolution (editing pot is an 8-bit value, MIDI is 7)
— Added “edit mode” which sucks. But allows you to stop holding down three buttons while you edit a sample.
— Removed some un- or underused softclock (timer) and Uart functions — we’re running low on flash memory.
— Divided AudioHandler routines into bank-specific routines for ISR speed BUT
–> this means we are way over memory. So, got rid of intro sequence, debug mode, all sawtooth stuff, removed some timer functions, changed MIDI handling (don’t recognize bytes we don’t use anyway), changed LED blink functions (all blink times the same)
–> Also kilt the random number init code. Changed pinning in multiply-output mode.

xo
TB

As of today, there are no more OG WTPAs!
The last 20 or so (of 200) took forever to get out the door.
Thanks, everybody, for helping make this happen. Thanks for all the feedback, and for the patience, and for giving me my first less-than-wack experience designing a product.

Hats off,
TB

(Note, there are still lots of benighted and lonely bare PCBs and microcontrollers for the H4RDC0R3)

Not content to rest on his laurels, Nick decided to build ANOTHER WTPA for his old friend Jonny who plays minimal techno on a fancy euro label as a present for bringing him over to Berlin to write some tracks. Again I had a chance to warm up the CAD deck and make this guy. He still has threaded holes, but everything is a little tighter than before. And he’s blue.

These cases were cut by my man Joe at Prototope who do a kickass job of laser cutting really fast, and are based in Manhattan.

By this time I got pretty convinced that churning out lasered cases was like falling off a log and figured the next WTPA ought to come with one as an option, albeit without the annoying thread cutting step.

xo
TB

Right around this time in the summer of ’09 my buddy Nick (who stuffs the WTPA kits, and who plays in a kickass band called Lazercrystal built a WTPA for his girl Lulu, Chicago bartender par exellence and all around lovely lady. I had been on an enclosure kick and decided that this was the time to get jiggy with QCAD for linux and actually make a reproducible laser cut enclosure. I still had to tap threaded holes in the edge panels, but everything fit the first time, believe it or not.

These are the results of that experiment and Lulu’s is still about the prettiest WTPA there is out there.
The buttons are a plunger extension made of acorn nuts, flathead screws, and spacers. They look good and work well but personally I find they feel a little hinkey.

xo
TB