Author Topic: z80-like portable computer for <$30! (If you build one) (Read 65766 times)

DJ Omnimaga · « **Reply #150 on:** April 04, 2014, 02:36:10 am »

Wow I watched this video above and the music really sounds great!

For some reasons I was expecting chiptune-like stuff (nes or sega style), although that would still have been cool. I am curious if that is still progressing btw? I'm glad you continued working on this, although I missed most of the updates lol.

Keoni29 · « **Reply #151 on:** April 05, 2014, 06:09:44 am »

I am waiting for the flash rom to arrive. Then I can continue working on the filesystem.

DJ Omnimaga · « **Reply #152 on:** April 05, 2014, 12:13:30 pm »

I see. Also did you manage to stay under $30 so far? I know sometimes that shipping fees can make a big difference (eg on Ebay some people charge $25 shipping just for a Magic card)

Keoni29 · « **Reply #153 on:** April 05, 2014, 12:47:45 pm »

For the prototype it is well over $30. The gameduino alone cost me $40+10shipping+$20tax+customs fees. It was pretty expensive.

aeTIos · « **Reply #154 on:** April 05, 2014, 12:48:48 pm »

That said, I think you didnt really follow the parts list eventually...

Keoni29 · « **Reply #155 on:** April 05, 2014, 12:53:21 pm »

Nope not really. The parts list was based on the old portable design. I kind of deviated from that idea. I might go back to it though since the operating system allows the use of multiple output devices. I only need to add driver code for an lcd screen.

Keoni29 · « **Reply #156 on:** April 06, 2014, 10:50:39 am »

I have been experimenting with floppydrives today. I found out that you can pretty much define your floppy's data density yourself if you write data slow enough. An IBM formatted double density floppy's shortest pulse length is 4microseconds. The eZ8 runs at 20MHz, so that is a minimum of 80 clocks per signal change. In order to simplify the operating system I will use a second eZ8 to control the floppy drive.

Streetwalrus · « **Reply #157 on:** April 06, 2014, 02:30:27 pm »

Oh that's pretty cool. I think the same goes for HDDs actually.

Keoni29 · « **Reply #158 on:** April 06, 2014, 03:02:59 pm »

I am still figuring out how this works, so this information is not 100% correct!
Old hard drives use the same magnetization patterns as floppy disks. It is called MFM (Modified Frequency Modulation)
I just read a datasheet of a diskette drive. Data is stored as changes in the magnetization layer. On a transition a short low pulse can be detected at the DataRead pin of the drive. The time in between those pulses represents a bit pattern.
2us pulse = a > next up: a
3us pulse = ab > next up: b
4us pulse = ab > next up: a

Example of a pattern starting with logic 1.
Pulse length: 2 3 3 4 ... Bit pattern: 1 10 01 10 1...
The byte on the end

I do not know how the start of a sector is marked yet though.

DJ Ryan Knutson · « **Reply #159 on:** April 06, 2014, 04:06:29 pm »

Raspberry Pi anyone?

Streetwalrus · « **Reply #160 on:** April 06, 2014, 05:35:26 pm »

And here comes a troll who knows nuthin' 'bout retro programming. Nah jk.

I do have an RPi, and it's not the same thing at all. There is a nostalgic feel in making this, plus it's diy and more challenging due to limited resources.

DJ Omnimaga · « **Reply #161 on:** April 07, 2014, 01:35:30 am »

We have to understand that the new generation of kids for the most part have never heard of anything other than the Xbox One and Playstation 4.

They don't even know the Playstation 3 nor the Xbox 360 exists and think that gaming started the day they got their first console and to them, any game (other than Minecraft and Flappy Bird) that has worse graphics than Call of Duty: Ghosts, is worthless.

Seriously, though, what Street said. The Raspberry Pi is *not* an old school computer. Keoni29's Z80 computer, which uses a 30 years old processor, on the other hand, is.

aeTIos · « **Reply #162 on:** April 07, 2014, 02:29:19 am »

Quote from: DJ Ryan Knutson on April 06, 2014, 04:06:29 pm

Raspberry Pi anyone?

Not sure why this dude got downvoted on this post though, its not like he really meant to troll (at least I hope so

)
Voted up to compensate because I feel like that post doesnt deserve it.

Quote from: Keoni29 on April 06, 2014, 03:02:59 pm

I am still figuring out how this works, so this information is not 100% correct!
Old hard drives use the same magnetization patterns as floppy disks. It is called MFM (Modified Frequency Modulation)
I just read a datasheet of a diskette drive. Data is stored as changes in the magnetization layer. On a transition a short low pulse can be detected at the DataRead pin of the drive. The time in between those pulses represents a bit pattern.
2us pulse = a > next up: a
3us pulse = ab > next up: b
4us pulse = ab > next up: a

Example of a pattern starting with logic 1.
Pulse length: 2 3 3 4 ... Bit pattern: 1 10 01 10 1...
The byte on the end

I do not know how the start of a sector is marked yet though.

Cool stuff thar keoni!

Keoni29 · « **Reply #163 on:** April 07, 2014, 05:40:59 am »

It is tough to find all of this information condensed in one webpage/datasheet, because the technology is obsolete. I bet there are some great websites out there, but they have been buried below thousands of floppy drive music tutorials.

TIfanx1999 · « **Reply #164 on:** April 07, 2014, 06:28:42 am »

You're probably right since music seems to be the thing most floppy drives are used for these days.

@Aetios: I don't think it was meant to be trollish either. Hard to say since it was such a short and vague comment.

The point with this machine isn't just to have access to a cheap old school machine. It's about the process of going through and doing it yourself. That's what makes it interesting. So while the end goal may be similar, this is a more involved process.

Author Topic: z80-like portable computer for <$30! (If you build one) (Read 65766 times)

DJ Omnimaga

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

DJ Omnimaga

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

aeTIos

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

Streetwalrus

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

DJ Ryan Knutson

Re: z80-like portable computer for <$30! (If you build one)

Streetwalrus

Re: z80-like portable computer for <$30! (If you build one)

DJ Omnimaga

Re: z80-like portable computer for <$30! (If you build one)

aeTIos

Re: z80-like portable computer for <$30! (If you build one)

Keoni29

Re: z80-like portable computer for <$30! (If you build one)

TIfanx1999

Re: z80-like portable computer for <$30! (If you build one)