2-digit LED display for memories?

gmeredith · Posted: Thu Apr 18, 2013 9:19 pm Post subject: 2-digit LED display for memories?

Hi, haven't posted here for ages but still lurk occasionally.

I've done a sample memory expansion on my Casio DM100 keyboard. I've expanded it to 16x the sample memory, so that it has 16 banks of 4 samples:

http://www.warningwillrobinson.com.au/index_files/Professor.htm

I've also done it to my Casio SK8.

I'm trying to make up an improved LED display to select and show the memory bank number it's on. At present I'm using a single digit LED display. I'd like to go to a two-digit display.

The 16 memory banks are presently selected using a 4029 up/down counter chip going to the expansion chip's 4 extra memory address lines. These 4 lines also input to a 4511 display encoder driver and 7-segment LED digit as the display.

In this instance, memories 0 to 7 (ie the first 8 memories) are displayed as 0 to 7 on the display. but because the 4511 display chip won't decode and display binary numbers past 9, I'm stuck with only accessing 0-9 memory banks. How would I make a 2-digit display to show the numbers 11-15? I'd rather not go down processor/PIC/Arduino solutions for this because I'm not into programming nor have the gear.

I notice that the 4029 chip has a "carry" feature. Is this what this is for? Access a 2nd 4511 chip for a cascading 2 digit display?

Cheers, Graham

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PHOBoS · Posted: Fri Apr 19, 2013 2:42 am Post subject:

interesting,. I have an SK1 myself that still needs to be modified, and memory expension would be great Shocked

As for the displays, I wanted to drive a couple of displays a while back and if I remember correctly this either needed some special cmos/TTL chips
(which are no longer available) or a lot of extra logic which wasn't worth it in my opinion. So eventually I did use a PIC (not what you want).
So I'll keep my eye on this thread in case someone offers a solution.

you could do something else, that is use the dot on the display to indicate higher numbers. So use 3 bits to control the display from 0-7 and use the
4th bit for the dot which indicates 8-15.

gmeredith · Posted: Fri Apr 19, 2013 3:52 pm Post subject:

Actually, yes, that's what I had been doing before I went with the 4029 counter - I had the 4511 hooked up to the lowest 3 address lines and the 4th to the dot. It's okay, and simple, but I just wanted something more aesthetic and user-friendly. If I can't find anything simple I'll go back to that.

Is there anyone out there that sells pre-programmed PIC chips to do this?

I'm amazed to find out how difficult it seems to be to do such a simple job. Surely there's some driver counter chip that simply overflows any number over 9 to another digit?

Cheers, Graham

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

I recently built a two digit counter using the same IC's. there is an incorrect schematic somewhere on the web where the cascading will not work correctly. I'm away from home for a couple more days but I will check and see how I did this. I think you replicate your counter and decoder for the second display and take the carry out pin (pin 7) of the single digit/units, to the carry in pin (pin 5) of the double digit/tens. The reset pins of the two counters are tied to set the count to 00.

PHOBoS · Posted: Sat Apr 20, 2013 6:11 am Post subject:

ah, a double counter yeah that would work in this case Very Happy

gmeredith · Posted: Sun Apr 21, 2013 5:22 pm Post subject:

Wow, thanks, minus! I'll give it a try soon and see how it works out. Thanks for your help!

Cheers, Graham

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

There is the CD40110 too. This is an up down counter and LED driver all in one chip. Using them would reduce the IC count.

http://www.ti.com/lit/ds/schs100/schs100.pdf

gmeredith · Posted: Mon Apr 22, 2013 4:16 pm Post subject:

Seems good - but where do you output the 4 address lines for a RAM chip?

analog_backlash · Posted: Mon Apr 22, 2013 6:12 pm Post subject:

gmeredith · Posted: Mon Apr 22, 2013 6:21 pm Post subject:

The memory expansion for SK5/SK8 is well established and documented - I wrote up a guide for it:

http://www.warningwillrobinson.com.au/index_files/SKexpansion.htm

The chip that is specified is no longer available for it (32x chip) but there is still a smaller one of the same kind that gives 16x expansion, and is used exactly the same way.

Cheers, Graham

-minus- · Joined: Oct 26, 2008 Posts: 787 Audio files: 13

analog_backlash · Posted: Tue Apr 23, 2013 6:32 am Post subject:

Thanks for the excellent guide Graham! When I'm feeling brave one day, I will have a go at this Very Happy

.

Gary

gmeredith · Posted: Tue Apr 23, 2013 4:32 pm Post subject:

I forgot! Here's an even better guide, with photos, taking you through every step of the process - it's for my DM100 keyboard - which has an sk5 as the upper keyboard:

http://www.warningwillrobinson.com.au/index_files/Professor.htm

It's down the bottom of the page, under the DM100 info.

So it will be exactly the same for your keyboard, except for a couple of hookup places on the board, which I could walk you through when you want to do it.