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 Forum index » DIY Hardware and Software
Check out my LED display for expanded memory SK8!
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gmeredith



Joined: Jun 28, 2006
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PostPosted: Thu Aug 10, 2006 11:51 pm    Post subject: Check out my LED display for expanded memory SK8! Reply with quote  Mark this post and the followings unread

Hi all,
I've just completed a digital readout for my 32x memory expanded Casio SK8. It's only a prototype, and it needs to be prettied up, but it's fully working and behaving properly.

It's a 2 digit LED display, to display the 32 banks of expanded memory I just did. The memory is arranged as 2 banks of 16 memories.

The first digit (the small one) displays the bank (1 or 2), the 2nd larger digit displays the 16 memories in each bank (0-15, as 0-9 then a-b-c-d-e-f for the rest).

The 2 banks are switched between using a simple toggle switch to switch on/off the highest bit address line of the RAM chip. This switch also connects power to the 1st digit's segments to form either a "1", or a "2". Simple!

The 16 memories in each bank are accessed using a push button that scrolls through each memory. This is driven by a 4029 cmos binary counter IC, switching the other 4 address lines of the RAM chip, which also drives a 4511 BCD-to-7 Segment Latch/Decoder/Driver for the readout (at this stage I couldn't get hold of a binary decoder driver quickly, so I used the 4511 I had lying around for the moment, and it only displays memories 0-9, the last 6 memories are not displayed - they will be when I get the binary decoder driver).

The momentary push button switch is used to pulse the 4029 counter through the memories. A 2.2uF 16v electrolytic capacitor wired across the button terminals acts as an effective switch debouncer.

Thanks to everyone on the forum here for their advice and input into this, it works great!

Cheers, Graham


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Last edited by gmeredith on Sun Aug 13, 2006 6:53 pm; edited 1 time in total
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dnny



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PostPosted: Fri Aug 11, 2006 12:23 am    Post subject: Reply with quote  Mark this post and the followings unread

thats cool.
glad to see you got it working.

for those who want to read on how to do this -> Successful 2x Memory Expansion for Casio SK5 and SK8!!

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bigtex



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PostPosted: Fri Aug 11, 2006 1:29 am    Post subject: Reply with quote  Mark this post and the followings unread

Wow, with that kind of memory you should try wavetable scanning. You could probably use an ADC to generate the value for the address and make it CV controllable. Crazy. I wonder if it would handle that kind of switching. Might sound terrible....
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v-un-v
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PostPosted: Fri Aug 11, 2006 5:14 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice Smile

Has anyone here seen the Saudi Arabian version of the SK8? You can play Arabic scales on it. Cool

I saw one on Ebay a couple of years back- they do exsist- honestly! I was very tempted to bid- but didn't want the hassle from my girlfriend Wink

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Blue Hell
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PostPosted: Fri Aug 11, 2006 10:00 am    Post subject: Reply with quote  Mark this post and the followings unread

v-un-v wrote:
Has anyone here seen the Saudi Arabian version of the SK8?


wondering ... would that really be a different version or maybe just a solder link on a PCB ...

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State Machine
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PostPosted: Fri Aug 11, 2006 10:50 am    Post subject: Reply with quote  Mark this post and the followings unread

Nice work Graham! beer Looks like you got most of the features you wanted! The initial thread was fun as the project developed.


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State Machine
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PostPosted: Fri Aug 11, 2006 10:53 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
wondering ... would that really be a different version or maybe just a solder link on a PCB ...


Sure, like when the CPU powers up, it reads a port bit that the link ties to and decides what version it is and how it shall behave. Very common in industry. Very Happy
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jksuperstar



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PostPosted: Fri Aug 11, 2006 2:06 pm    Post subject: Reply with quote  Mark this post and the followings unread

I love the 2 different sized LEDs! Makes for more character for your bend, instead of more vanilla like it was pre-made....but still looks good & clean. Congrats!
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v-un-v
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PostPosted: Sat Aug 12, 2006 1:25 am    Post subject: Reply with quote  Mark this post and the followings unread

Blue Hell wrote:
v-un-v wrote:
Has anyone here seen the Saudi Arabian version of the SK8?


wondering ... would that really be a different version or maybe just a solder link on a PCB ...


Hmm- yes. That's an interesting thought.

I bet it would be a right pig to find it- unless of course you had both side-by-side?

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ALLES TURISTEN UND NONTEKNISCHEN LOOKENPEEPERS!
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IST NICHT FÜR GEWERKEN BEI DUMMKOPFEN. DER RUBBERNECKEN SIGHTSEEREN KEEPEN DAS COTTONPICKEN HÄNDER IN DAS POCKETS MUSS.
ZO RELAXEN UND WATSCHEN DER BLINKENLICHTEN.
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gmeredith



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PostPosted: Sun Aug 13, 2006 6:51 pm    Post subject: Reply with quote  Mark this post and the followings unread

Thanks for the cheers, guys Very Happy
I've got nearly everything I wanted in the display, and learnt a whole stack of stuff in the process. I still want to make it actually display a real 2 digit number instead of hexadecimal for the 16 banks, but I think I know how it is basically done now. My next trick is to hook it up to MIDI program change!!

Regarding the Arabic scaling, the SK8 and the Arabic SK8a are one and the same machine, except for an external switch. All of the circuitry is there in the SK8 to turn it into an sk8a arabic. It is a common mod and only requires a 4 position switch and a diode wired into the vacant space for it on the circuitboard. You can find info on how to do it here at the Yahoo Casio SK Group forum:

http://launch.groups.yahoo.com/group/CasioSK/

It's in the FILES section on the site (you'll need to join as a member to get access to the files though)

Look in a folder called "Squelchbox Mods and Bends"

Also here:

http://users.informatik.haw-hamburg.de/~windle_c/TableHooters/Casio_SK-8.html

Cheers to all!

Graham
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gmeredith



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PostPosted: Mon Aug 14, 2006 11:28 pm    Post subject: Reply with quote  Mark this post and the followings unread

Just thought I'd upload the schematic for my display. As I've mentioned before, this circuit could be used to control anything, not just a RAM chip. It could be used to switch a bank of resistors or capacitors for "presets" in a VCA or VCF circuit, or anything!

Here is where I originally got the basic idea:

http://www.ee.ucr.edu/~stan/courses/ee120a_06spr/labs/Lab_1.pdf

Cheers, Graham


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