Connecting an HxC Floppy Emulator to an ST

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Revision as of 20:53, 26 June 2014 by Admin (talk | contribs) (Added instructions for an alternative approach using a single cable)
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The HxC is a great piece of kit. It will allow Atari users to run software/games straight from disk 'images' with no need to rely on legacy floppy drives that are fast diminishing through failures. Once those legacy drives are all gone, that's your lot!

For owners of the HxC, the conundrum is how best to use it. The Atari will not boot from Drive B (DS1) and most people would like the flexibility of retaining the internal drive for legacy floppy support (or aesthetic reasons). Also, If you own several machines (ST, Falcon, Amiga, PC, Mac etc), it would be nice to be able to hook the HxC up to any of them as required.

This solution provides a means to use the HxC as an external peripheral and attach it to the external drive port on an ST. A small modification inside the ST will provide the ability to swap the internal and external drive ID's around by the flick of a switch so you may boot from either source (See Drive Select Swap Mod)

Tools you will need

Phillips Screwdrivers

Soldering iron

Solder

Heat Shrink (Optional)

Small electronics-style side cutters

ESD protection

Drill or handheld hobby tool

Helping Hands (Optional)

Goggles

Gloves

Face Mask

Using an intermediate connector on a homemade enclosure

Parts list

Project Case - I used Maplin product code: LF11

14-Way Male DIN plug and 14way data cable - I ordered a ready made cable from 16/32 (http://sales1632.myzen.co.uk/acatalog/Atari_Cables.html)

15-Way Male connector - I used a 2-row type so as not to confuse it with VGA

15-way female connector

USB-B chassis mount connector

Veroboard

34-way IDC flat floppy cable


Mounting the HxC into a case

1. Desolder the USB connector and LED's from the board and replace the USB connector with a small run of USB cable (I have used a USB-A to USB-B coupler on my chassis. Consequently I have used a USB-A connector on a short run of cable):


2. Remount the LEDs onto a small piece of veroboard - bridge all the positive connectors together:


3. Cut all the necessary holes in the chassis for the LED array, USB socket and 15-way male DSUB.


4. Wire up the LED array to the HxC board as shown here:


5. Wire up the 34-way flat cable to the 15way DSUB (Using all these lines means you can use the HxC on non-atari hardware also):

34w - 15w

2 ------ 1

8 ------ 9

10 ---- 2

12 ---- 10

14 ---- 3

16 ---- 11

18 ---- 4

20 ---- 12

22 ---- 5

24 ---- 13

26 ---- 6

28 ---- 14

30 ---- 7

32 ---- 15

34 ---- 8

ANY ODD LINE - Shielding (see my pic - the one with the heat-shrink around it)


6. Finished assembly:


Peripheral Cable

Note, I think there is a small error below. DSUB pin 2 (Motor Enable A, pin 10 of the 34w) is connected to DIN pin 5 (Drive 0 select). It would make more sense to connect pin 3 DSUB (Drive Sel A, pin 14 of the 34w) to DIN pin 5, and DSUB pin 2 to pin DIN pin 8 (Motor on). Note that both pins 2 and 11 of the DSUB would be connected to pin 8 DIN, as the ST only has a single 'motor on' line. --Galax

Finally, here's how to make the cable for your new peripheral:

15w DSUB --- 14w DIN

1 -------------- NC

2 -------------- 5

3 -------------- NC

4 -------------- 9

5 -------------- 11

6 -------------- 13

7 -------------- 1

8 -------------- NC

9 -------------- 4

10 ------------- 6

11 ------------- 8

12 ------------- 10

13 ------------- 12

14 ------------- 14

15 ------------- 2

SHIELD ----- 3 + 7

Connecting the ST to the HxC with a single cable

If you have bought one of the more recent cased HxC rev C drive emulators, or you want a simpler cable solution, you may want to connect the ST directly to the HxC with no intermediate connector. If you don't feel confident enough or can't be bothered to make this, contact Galax about having a cable made.

Parts list

Qty | Digi Key # | Manufacturer #    | Description
----+---------- -+-------------------|------------------------------------------
1   | OR981-ND   | Omron XG5M-3432-N | CONN DBL ROW SOCKETS 34POS AWG24
2   | OR943-ND   | Omron XG5S-1701   | CONN SEMI-COVER 17POS FOR XG5M
0.5 |                                | Atari ST male-male 15 pin DIN floppy cable

(You only need half a floppy cable, as you can cut it in two and use it to make two of these cables)

Connector Pinout

34 Way Connector on HxC  = 15 Pin DIN Atari ST Floppy Connector
------------------------   ---------------------------------------
2  Density Select        =  
4  Reserved              =  
6  Reserved              =  
8  Index                 =  4     Index Pulse     (yellow)
10 Motor Enable A        =  8*    Motor On        (dkbrown*) 
12 Drive Sel B           =  6     Drive 1 Select  (purple)
14 Drive Sel A           =  5     Drive 0 Select  (dkgreen)
16 Motor Enable B        =  8*    Motor On        (dkbrown*)
18 Direction             =  9     Direction In    (orange)
20 Step                  =  10    Step            (grey)
22 Write Data            =  11    Write Data      (pink)
24 Floppy Write Enable   =  12    write gate      (ltblue)
26 Track 0               =  13    Track 00        (ltbrown)
28 Write Protect         =  14    Write Protect   (ltgreen)
30 Read Data             =  1     Read Data       (red)
32 Head Select           =  2     Side 0 Select   (white)
34 Disk Change/Ready     =  
Any Odd Pins             =  7 + 3 Logic Ground    (black + dkblue)

* Both Motor Enable A and B are connected to the ST's Motor On (makes sense to me!)

The colours refer to the wires in my ST floppy cable. No idea if these are universal, but it may speed up your continuity checking a bit!

I stripped and tinned the wires before pressing into the 34 way rectangular connector, because I was only prototyping it at first. You should be able to just crimp the insulated wire into the connector, which is quicker and easier.

A handy guide to the pin numbering of the ST's 15 pin floppy connector is here, remember that this numbering is of the socket on the ST as you look at it, so when you hold the plug of the cable facing towards you the numbering would be mirrored: [1]

Jumper settings

Jumper settings for HxC as both drives A and B. You can boot from the HxC's drive A in this mode. This works perfectly with an ST or STM, but the internal floppy drive should be unplugged with an STFM, STE, etc.:

Jumper settings for HxC as external drive (HxC thinks it is 'A' which is the default on power up, ST sees it as 'B'. Only 1 jumper is connected, the one on the right is just half plugged in so I don't lose it):

Power cable

You'll also need a power cable, I connected the +5v and -ve pins from a recycled USB cable to an old connector that I adapted, would be easier to buy the correct adapter.




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