Plus4 SD/MMC

SO, I've spent much of the day soldering away, and I've almost got the MMC part connected up. It's hard going though, and to top it all I think my soldering iron needs a new tip - again. The more I do of this, the more I wish I had that milling machine so I could just make a new board! Soldering in the sockets etc. is nothing, but stripping and soldering the wires is a nightmare!

Any-hoo, once I've done the last few wires, I'll try the code I have for reading the card and see how close I got...chances are it'll need lots of tweeking to get it working right.

SD/MMC+Clockport Prototype

So here we go again....I've started the SD/MMC+Clockport interface. While it should be fairly simple, I've not connected a clockport before, and I need to decode the lines pretty much down to the byte this time; for both the clock port and the MMC interface. This means the board is pretty full so I won't be able to add the RAM to this test one,but if I was making a proper board, theres nothing saying I couldn't do it on that. While I couldn't see any real use for a RAM only interface, this one I can (with or without the extra RAM). Having an MMC card slot and a clockport on a card would be pretty cool, and allow all manner of C64 apps to be ported, along with allowing the +4 onto the Net - or simply better comms to the PC. But best of all really is that anything that someone makes for the C64's Clockport, would be usable on the Plus4 (with a little relocation - something +4 guys are pretty good at!).

Of course, if I added some RAM (128k,256k or 512k extra) it would mean that any clockport applications (like a TCP/IP stack or game) could make use of it, since you'd know everyone else running it would have the extra RAM as well. The only thing that worries me is the physical size of the interface. The C64 one is full of surface mount stuff - professionally done, but I guess this wouldn't be....

Oh well... first things first - lets get a working prototype and then worry about the rest of it!


Edit: Oh! And the little voltage regulator at the top, was just to see if I could solder one on without making a complete hash of it!

Getting orginised.

Yup, not been doing much.... A load of chips/parts have arrived so I've spent a couple of days sorting out my parts bin into some sort of order. I got fed up with not having the chips I needed/wanted, so I'm slowly trying to buy a few of everything (common chips at least), buit this means making some space for things.

I've also managed to source some pin headers for the clockport stuff, so Im going to start wiring up a SD/MMC+Clockport interface for the Plus4 next then I can start to have some REAL fun!!

I still need to finish doing the basic directory on the MMC, but that shouldn't be a big issue, and then loading a file should simply be a matter of getting the inital cluster from the directory entry, and reading it in.

I'm kinda looking forward to playing with the clockport the most, as it could mean some cool off the shelf toys for folk. The ethernet contoller looks the most fun, and I have the UDP slave source here to try out. Could be good!!!

I'm off to SigGraph in SanDiago next friday (3rd Aug), so I'll be back on XeO3 at that point, and I hope to get some stuff done on the plane again; but as usual it depends on how close the bloody seats in front are!

MMC Success!!

And here you go!! The ROOT directory in all its glory! I'm not parsing past the end of the 1st sector, but thats okay for now. I can now plug in any card (I have 3; 32Mb, 256Mb, 2GB - all FAT16) and I can display the ROOT directory of each of them. I guess the next thing to do is load a file from it..... or I could finish displaying the root directory, and sub directorys of course. But loading a file is pretty exciting stuff :)

I dont really want to get too far into it, as the main goal is to do a Plus4 version, not a C64 one. Although the code will be identical so its not wasted work.

Another big thanks to TNT for helping be get started with this....

MMC progress...

Well, I'm slowly progressing with my MMC card reading, I've gotten sector reading working okay, and from there read the boot sector with the partition information and then onto the FAT Mast Boot Record. However, I'm struggling to get from there to the root directory. The only info I have says that I use the root FAT+ReservedSectors+FatSectorSize = DirRoot, and while this works for one card, it appears to be coincedance.

Once I can get the root directory, it should be plain sailing to load a file. Each Directory entry points to a base sector (or cluster) and from there you use the FAT to cluster hop, reading in the file. I have to confess, I thought sectors were allocated rather than clusters and that sectors were resizable. But it appears that its the number of sectors in a cluster that changes. oh well, its much the same I guess.

Once I have a file loading, I'm going to build a Plus4 interface - or add it to my MemoryCard expansion, Im not sure...I guess it would be easier to build a seprate interface, although Im having a little trouble figuring out the best way of reading the card. The only way I can figure is using 2 flipflop buffers, one for in and one for out. However, the ChipSelect on the card may help with this, I havent sat down and worked it out yet.

Speed up!!

Well, thanks to a quick bit of spotting by TNT, Its down to around 11 seconds for 64k! Around 3 scanlines a byte - well cool... Thats actually usable as it is I'd say! And although it will slow down a bit (due to saving the output to the correct place, sector selction etc...) Thats still bloody good. Anyway, heres the brainwave TNT got...

GETBIT3 macro
        stx   port         ; Clock pulse
        sty   port         ;
        cpy   port         ; if Databit is 0, then Carry clear, else set.
        rol
        endm

Very cool indeed...Branchless, and 4 cycles per bit quicker... I NEVER would have spotted that one!!

MMC Reading...

Mmmmm....It just goes to show how well the MMC64 card was made. Currently I can load a full 64k in around 15 seconds (load is a loose term here...cycle through 64k of sectors is more like).

The MMC64 can load 61k in 3 seconds....damn thats fast! I think they allow proper access to it rather than SPI mode where the CPU "clocks" the bits in. I can probably speed that up by putting a PIC on there and having BYTE access to the card. But thats a LOT of work.

If I put a byte Read/Write port in there, then got the PIC to do the bit talking, then the Plus/4 could just read/write bytes. I guess that would be a x8 speed up (ish), but it might be a bugger to do. That would be almost on par with the MMC64 though, and with the higher clockspeed of the Plus4, I might even beat it.

I swapped the DataIn line from bit 3 (0-7) to bit 7, which meant I could use the BIT instruction to read it, there by freeing up the A register. So now I have a macro to read a bit like this...

GETBIT  macro
        stx   port      ; Clock pulse
        sty   port      ;
 
        asl             ; Shift incoming data to make space for new bit
        bit   port
        bmi  !skip   ; Bmi is reversed
        ora  #1
!skip
        endm

This is a special ReadSector() call used when reading the actual data (does 4096 BIT reads - 512 bytes), the write is longer and far slower, but doesn't get used nearly as much. Before I moved the bit from 3 to 7, I had to LDA, then AND, then deal with memory etc.... but by using BIT I can and the AND from memory without affecting anything else. I suspect this is about as fast as it can go via the user port.

MMC/SD reader....

Well, I've managed to get basic reading working, or rather the basic circuit and reading using the sample program. However, thats half the battle. I was struggling a little due to lack of proper chips, but I've managed to pick up the correct ones, so I'm back on track. I'll get the core Init/Read/Dir working, then I'll switch to the Plus/4 and see how I get on from there.

I suspect that I'll do it as an expansion card and not USER PORT plug-in though, as it allows me to download via my cable to program it - and perhaps even use my remote debugger which is partly written.

RR-Net and MMC cards

I've been playing with a cool little design for an MMC card reader on the C64, mainly so I can understand it and then try it out on the Plus/4. I've had to modify it a little as I dont have the chip he's using, but it should still work okay.

It's a user port based one so is easy to play with, but it did mean I couldn't use my download cable! Damn! However, now that I have an RR-NET, I found a cool little program called udpslave, which is exactly like my download program anyway, but over ethernet! Very neat. it also means you dont need a parallel port anymore, so I could use a laptop.

The more I look at these things the more I think it would be very cool to have on the Plus/4. Its another fairly simple addition I could add to the memory expansion I guess, as it only needs 4 bits of memory (3 out,1 in).

Its in situations like this though, that I'd KILL for a proper remote debugger! This is the reason you need to step through the actual code on the real machine...Oh well.. back to printing to the screen I guess.

Clockports, RR-Net's, SilverSurfer's.....

I just bought a RR-Net and SilverSurfer and have been playing with them a little, and I'm pretty impressed I have to say! Since both these products are modules that just "plug-in", they would work just fine on a Plus/4, and all you need is to be able to map the port into a set of hardware registers - a GAL would work just fine for that! You can do it pretty simply with a couple of other chips, but GAL's are really cheap, and make development really easy, so sod it :)

Anyways.... TNT kindly provided me with a link to the data, so I thought I'd post it here (so I dont lose it mainly...).

                  CLOCK PORT 

                   +--+--+ 
         GND       | 1| 2|   VCC (+5V) 
                   +--+--+ 
         /INT      | 3| 4|   /SPARE_CS 
                   +--+--+ 
         /RTC_CS   | 5| 6|   /PWR_BAD 
                   +--+--+ 
         /IORD     | 7| 8|   /IOWR 
                   +--+--+ 
         A3        | 9|10|   A2 
                   +--+--+ 
         A1        |11|12|   A0 
                   +--+--+ 
         D7        |13|14|   D6 
                   +--+--+ 
         D5        |15|16|   D4 
                   +--+--+ 
         D3        |17|18|   D2 
                   +--+--+ 
         D1        |19|20|   D0 
                   +--+--+ 
         GND       |21|22|   /RESET 
                   +--+--+ 
 
 
 
Connection to C64 Expansion Port 
---------------------------------
 
 
  Clock Port Signal   |   Expansion Port Signal 
----------------------------------------------------- 
            GND      <=>  GND (22 and Z, not 1 and A) 
            VCC      <=>  +5V (2 and 3) 
            /INT     <=>  /NMI 
            A0-A3    <=>  A0-A3 
            D0-D7    <=>  D0-D7 
            /RESET   <=>  /RESET 
 

This should be really easy, and although you won't get NMI's, things like RR-NET don't use them anyway, and you can always POLL the hardware instead - pretty neat. I might even try and add it to my RAM expansion, as I need to decode other stuff there anyway.