Space Base - A homebrew ICB/ZP

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Le Chuck:
It's all good, I didn't take it as an attack, just wanted to clarify where you were going. I've done quite a few "hacks" on my projects through the years and am usually quite proud of them. So far this project is hack free tho (unless you count the home made drive wheels and mounts) and that's because I very much want this to be something that can be replicated. Hacks add a lot of complexity. There's a reason you don't see a lot of wireless hot-swappable TRON sticks with in-game switching from 8 way to 4 way for the light cycle level. It's a holy rolling PITA to setup right.

We have discussed moving to PWM equipped motors but it's a price hike of about $30-$40 iirc. I've already installed the units and tested them out using the micro maestro to put them through a full range of movement on the actual playfield with no issue, in fact, because I was using simple movement scripts just for a quick test I had trouble getting them to go slow enough for the game to be playable. I could get a "crawl" pretty well but then I'd jump to "instant death" with the next speed hike - again just me fiddling in the garage and not using any of IDS's code or work he's already done.

If they don't work then we just move up to the next more robust option. At roughly $10 a pop they are too good to not test all the way to ground. If they don't work flawlessly and consistently we'll move on. That's the reason I haven't posted the full parts list, I don't want anybody to waste any money on something that might go into the proto/Alpha Unit but doesn't go into the final.

I'll let IDS address the rpi as that's more in his wheelhouse.

ids:
The pi - yeah, it really is overkill when used just for audio. It was not an easy decision for that reason, but I could not find anything which could come close to it in either price OR performance. For the same price as a pi model A, you can get some rudimentary things to play a single audio stream. I've also seen other boards at twice the price unable to do what a pi can do with audio. We also wanted the ability to overlay sounds - so we could have the background music going, then overlay some effect or voice at key moments. I had put a lot of effort into optimizing code on the Freescale to pull audio (uncompressed waveform data) from an SD card, push it out through the DAC pin and through a simple amp chip, but this was limited in capability (bitrate, single stream, etc) and consumed a lot of cycles, make game code more challenging.

The pi can not only play most any format of audio, as well as combine multiple streams, it also has SD built in - this simplifies the microcontroller code further by removing support for SD and freeing up some pins. The config file and high-score are stored on the SD. Offloading functions to a complete separate unit has other benefits as well (freeing up compute cycles, parallelism, ...)

So, as of today, the freescale connects to the pi via USB, and they use serial over USB to talk to each other. The KL25z is "master" - sending commands to the pi, and getting basic responses back. Commands include "play that tune", "give me the config file", etc The serial baud rate is set quite high so it's not a terrible burden. It's working well so far.

One last point - as was stated earlier, the pi can do so much more. And the latest pi's have many more I/O pins as well. To my knowledge, however, there are no pin driven interrupts, and there are other limitations (#pwm pins, preemptive multitasking OS issues, voltage and current considerations, etc) that make it unable to take over everything the KL25z is doing. If I thought the pi could do it all, I'd drop the microcontroller.

That's my $0.02, fwiw

SavannahLion:
I wasn't thinking of having the Pi pick up the IO. I looked at that too and, quite frankly, it's better to treat it like a computer rather than to try and make it a glorified micro some are so apt to do.

I was thinking along the lines of things like, are you able to push new firmware out to the KL25z from the Pi? I intend on including the tools to push new firmware to my child modules. Package an update and, in theory, the entire system updates itself.

I didn't consider leveraging the Pi for the SD card to get config data. I didn't think in that direction. Did you consider the B version to send high scores to a central server? Or to push firmware or game mode updates remotely via the network?

ids:
Some interesting ideas I had not considered, and if time permits, we may get there one day. The pi code could obviously run on either model, I was just trying to keep costs down with the 'A', didn't see the need for an extra USB port and the ethernet port, but you present reasons why it might be desirable. OTOH, you could drop in a USB based wifi adapter into an 'A' and go wireless as well. Lots of options, but until i finish the game code....

Thanks.

eds1275:
I have a few more days with my niece visiting, she is helping me finish up the smurfs machine and her own little Arcade Safari machine, but after that (starting tuesday next week) I will be back bouncing down existing audio and working that panic tune.

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