Alternatives to cassettes?

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Joined: Mar 23 2005
Posts: 19

Cassette interfaces are going to cost $20-30. On top of that, I haven't had a cassette recorder in years, so I'm wondering about alternatives. My project is something closer to a KIM-1 than an Apple-1 because of the cost differences (I'm working on a college student's budget to design an after school program for kids to build something they can tinker with and teach them how to do so. I may have to provide much or even all of the funding for this program, so a $5 savings in parts is going to be huge..)

Basically, the cassette interface is going to cost so much for something that so few of the kids are going to have access to at home. I mean, there are three cassette recorders in the classroom, but in this day and age you almost wind up wondering how many of these kids have ever seen a cassette before. Wink Most of them have more modern computers at home they can play with, but that isn't going to help them either.

Then I got to thinking about flash memories. I'm already using an EEPROM for the monitor and standard I/O routines, why not another wired up through a simple cartridge connector? Since it effectively looks like non-volatile SRAM with a write protect to the rest of the system, it would be easy to do. Or I could set up, with very little extra hardware, something that looked like a disk controller.

That part about disk controllers got me thinking: as cheap as an 8k EEPROM is, once you have something that you can actually remove from the system via a card connector or something, you're going to have something that costs as much as the cheapest camera flash cards. On top of that, the cards would be readable only by this thing, unless I were to build another interface to connect it to a parallel port. Of course, that would require that I had a parallel port, which isn't standard equipment on a mac. Wink

I'm wondering if it might not just make sense to use a "normal" flash memory device in a multicard reader. SmartMedia would be the most obvious choice (though it's getting kinda rare) because it's about as simple as the EEPROM, but perhaps CF is a reasonable consideration? What I'm pretty sure, at this point, is that supporting any form of FAT on such a memory card is more trouble than it's worth. Still requires "special" software on the host-side, but UNIX and MacOS X would be easy--I'm not sure about Windows offhand.

Are there other ideas I'm not considering? Any suggestions or ideas? Since I don't have an existing DOS (or at this point even a monitor), I pretty much have all of the options and none of the limitations for the time being. =)

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Joined: Mar 9 2005
Posts: 79
I've seen an ipod load softwa

I've seen an ipod load software into a cassette interface.

Something that is already compatible with the Apple 1 is the Disk-On-Chip 2000. Its a 32 pin dip chip, so you'd need to make two jumpers. It is a device that has 4k of flash memory access and then provides access to the other 16MB-1GB flash via entry ports in memory space. It would be easy to impliment with the least headache.

It depends. For me, the more junk that is added to the unit, the less it is an Apple 1 and the more it becomes just compatible with running the monitor. A few registers and latches and we could wire up a quick and dirty mmu. Throw 16MB of ram at the thing. Wink

If you have not found it already, do a search for GeckOS. There is a link to it at 6502.org.

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Joined: Mar 23 2005
Posts: 19
Re: I've seen an ipod load softwa

logjam wrote:

I've seen an ipod load software into a cassette interface.

Compress your 4k program down to 1mb for your mp3 player, yeah! Wink

logjam wrote:

Something that is already compatible with the Apple 1 is the Disk-On-Chip 2000. Its a 32 pin dip chip, so you'd need to make two jumpers. It is a device that has 4k of flash memory access and then provides access to the other 16MB-1GB flash via entry ports in memory space. It would be easy to impliment with the least headache.

Well, that would definitely reduce overall headache on the 6502 side, but it wouldn't do you any favours on anything else—you'd still be trying to build an interface board to have the thing accessible on a more modern machine. The thing I'm trying to do here is come up with a way to let the kids use an assembler and then load the generated binary code into volatile RAM, maybe make some changes, save it back, etc. Granted this is a simple solution for more storage than you could ever reasonably use, but it's also one of the more expensive options available.

Remember, I'm targetting this for a group of thirty kids at a school in a poor neighborhood. I'll be eating most or all of the costs of this program myself.

logjam wrote:

It depends. For me, the more junk that is added to the unit, the less it is an Apple 1 and the more it becomes just compatible with running the monitor. A few registers and latches and we could wire up a quick and dirty mmu. Throw 16MB of ram at the thing. Wink

If you have not found it already, do a search for GeckOS. There is a link to it at 6502.org.

I've seen most everything at 6502.org by now, including GeckOS. I point out, for the record, that the thing I am cooking up here has more in common with the KIM-1 than the Apple-I simply because I don't intend to spend money on things like video hardware. May go for an enhanced monitor that uses a 20x4 LCD panel, if I can get LCD panels cheap enough. As I said, I'm not building one of these things, I'm building one, and then I'm going to help kids build thirty more. Laughing out loud

I can always write more software. It's the cost of that hardware that's going to get me.

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Joined: Mar 9 2005
Posts: 79
BGMicro has a 40x2 with backl

BGMicro has a 40x2 with backlight for $5.95

Now I understand your situation a little better. Most of my design considerations are for clocking the thing up to 14MHz.

I would use a Unitron 28SX microcontroller to hault the processor and then use the SX's serial port to read/write memory locations.

If done right, the SX could even have a mode where its serial port is memory mapped to the 6502. Wink The SX and maxim would probably cost $5.

Will they be making these things on protoboard / solderless breadboard?

Will they be using Windows workstations? I could be convinced to make the microcontroller firmware and a cheap VB program to help the kids. A memory debugger would be handy to have anyway. Something with Run/Stop/Step and the ability to read/write memory locations...interesting... Wink

BGMicro has some interesting keypads : ACS1284, ACS1048, SWT1067

They also carry the ram, eeprom.

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Joined: Mar 23 2005
Posts: 19
Re: BGMicro has a 40x2 with backl

logjam wrote:

BGMicro has a 40x2 with backlight for $5.95

Now I understand your situation a little better. Most of my design considerations are for clocking the thing up to 14MHz.

Yeah, that's a very different target. Wink A good one, though. http://www.elexp.com/ is so far winning my business from the likes of Jameco and Digikey since they can actually provide the stuff I want at a more affordable price than the others. I haven't looked at BGMicro.

logjam wrote:

I would use a Unitron 28SX microcontroller to hault the processor and then use the SX's serial port to read/write memory locations.

If done right, the SX could even have a mode where its serial port is memory mapped to the 6502. Wink The SX and maxim would probably cost $5.

Will they be making these things on protoboard / solderless breadboard?

The first machine built will be my prototype. I last played with this kind of thing when I was 13, and I am now 26. I have my basic knowledge of logic, of the 6502 from hours of Apple // hacking, and a good enough understanding to know what I won't need, but only a good guess as to what I might. Time to break out TTL and CMOS cookbooks and reteach myself everything I can't remember anymore.

Thanks to the nice people at the above referenced URL and their reasonable price on a solderless breadboard kit big enough to actually accomodate the whole damned logic board for under $20 (it doesn't have nearly enough precut wire, but I can cut my own damned wires!), I'll be breadboarding first. Once I'm satisfied, I'll move the design to wirewrap. Probably I will refine the design to be very similar to what the kids will actually be building at this point and cook up the instructions for doing it.

I'll probably build a second logic board using the instructions to prove the final design the kids will be building actually works without the extra crud likely to get wired in to the first prototype. This too will be wirewrap, as will what the kids build. (In our litigious society, giving them a lethally hot implement to melt metal probably isn't going to fly..!)

Part of the reason for the second prototype is that I am making some big assumptions in the first one, such as that I have no idea how much power I'm going to need, so I'm building it with a 3 amp power supply. Wink I'm also likely to decode address lines for a second EEPROM which will sit in a ZIF socket so that I can copy updates I make to the standard calls and monitor quickly/ The second one literally has to be exactly what the kids will build.

Some of what I have decided will go in is a hex keypad and some form of hexidecimal display. It need not necessarily be alphanumeric or anything. There should also be a serial port and some means for long-term storage other than the onboard EEPROM, though exactly how we'll do that I don't know yet.

logjam wrote:

Will they be using Windows workstations? I could be convinced to make the microcontroller firmware and a cheap VB program to help the kids. A memory debugger would be handy to have anyway. Something with Run/Stop/Step and the ability to read/write memory locations...interesting... Wink

The classroom I work in during my time at the school in question has a number of ifruit and older macs, all running OS/9. There are some Palm PDAs, and there may be options for serial interface there with a proper isolator circuit. I am interested in the firmware, of course, but the best bet for interfacing with it might be my little $300 ASUS Sempiron baby-barebones system running Linux and a parallel or serial port interface.

The disk idea is really might be a good target for smallest available capacity flash memory cards. Smartmedia, despite being rare now, is literally just an EEPROM in a weird package. CF is basically just IDE, and IDE is generally just buffered data lines. I wonder though about some of the serial formats, like MMC. You couldn't use SD cards because of the DRM tech, but MMC cards are cheap, especially in quantity of tiny capacities.

Then again, memmap of a big EEPROM may wind up the most reasonable solution, looking back at the datapod on 6502.org.

logjam wrote:

BGMicro has some interesting keypads : ACS1284, ACS1048, SWT1067

They also carry the ram, eeprom.

I like one of their cheaper DMMs, it's like mine only it has more features, more range, and costs less than I paid for this one. Wink I note they also have 6522 and 6551, but no 65C02s. Jameco has these "refurbished" for $7, and that's about the only place I've seen aftertising a per-unit price online.

I think I see the keypad you were referring me to. If he still has these, he's likely to have at least one less, and possibly very soon several more less. Laughing out loud

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Joined: Mar 9 2005
Posts: 79
Is there a reason you are not

Is there a reason you are not going to use a microcontroller like an AVR? They can be programmed by a Mac OS/OSX, linux, windows, etc. A lot easier to prototype IMO...

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Joined: Mar 23 2005
Posts: 19
Re: Is there a reason you are not

logjam wrote:

Is there a reason you are not going to use a microcontroller like an AVR? They can be programmed by a Mac OS/OSX, linux, windows, etc. A lot easier to prototype IMO...

Besides that I grew up speaking 6502, you mean? Smile

Joined: Apr 22 2005
Posts: 4
I have seen a picture of an e

I have seen a picture of an EPROM board on here, but how would I go about making one for my Replica?