nilseuropa / sdpp

SD Card to Parallel Port Adapter and MS-DOS Driver

SD Card to Parallel Port Adapter(s) and MS-DOS Driver

"A long forgotten solution that gets updated every decade or so. [ 1994 - 2014 - 2024 ]" It's either the update rate is doubling - and the next update will come in 2029 - or it is coming in every year that ends with a four... Anyway, I wanted to have a single repository to contain all information to keep this neat solution afloat. This is it.

Parallel port power

Current version of the MS-DOS driver supports powering the SD card via the parallel port. A modern micro SD card takes around 25mA of current on 3.3V in average. There are five data channels that are utilized as power outputs:

Adapter	DB-25 Pin	Parallel Port
VCC	5	Data 3
VCC	6	Data 4
VCC	7	Data 5
VCC	8	Data 6
VCC	9	Data 7

IEEE 1284 Level II interface drivers must be able to source 14 mA current (at least +2.4V voltage) and also sink 14 mA current (output voltage lower than 0.4V). The output impedance in normal operation range is defined to be 50+/-5 ohms.

Port type	Normal	UM82C11-C	IEEE 1284
Data output (>2.4V)	2.6 mA	2 mA	14 mA
Data line sink (<0.4V)	24 mA	24 mA	14 mA
Control output (>2.4 V)	0.5 mA	1.5 mA	?
Signal lines (short circuit)	1 mA	?	?
Control line sink (<0.4V)	7 mA	7 mA	14 mA

⚠️ WARNING, using this feature can potentially harm your port driver if it is not IEEE1284 compliant!

As this standard came alive in 1994, rule of thumb is that most computers built after it are probably compliant, and everything before that is a mystery that you have to solve for the sake of your machine. The power feature is totally optional, and potentially dangerous if your machine doesn't support it.

Hardware options

1. Hook up an SD breakout board to a DB25 and be done with it ( see Wiring )
2. Etch my simple adapter board design for the breakout module
3. Build my SD Drive design ( contributions are welcome )

SD Breakout board

In principle any SD card connector breakout board can be used that has 3.3/5V level shifters and a voltage regulator - like this one:

⚠️ Do not use breakout boards without level shifters! You will most likely damage your card.

Wiring

SD Adapter	Hint	DB-25 Pin	Parallel Port
CS	Chip select	4	Data 2
SCK	Clock	3	Data 1
MOSI	Card serial in	2	Data 0
MISO	Card serial out	13	Select
VCC	+5V DC
GND	Ground	25	Ground
Optional
CD	Card detect	11	BUSY

Breakout Adapter

Schematic diagram

Disregard the barrier diodes in case you want to build a fool-proof circuit.

Etch it yourself at home board

This is an easy to fabricate adapter board for the micro SD card connector breakout module depicted above. It is available through at least 5 vendors. ( The one I have came from Reichelt. )

Double check that your port is IEEE1284 compliant. The circuit also provides an auxiliary power input through barrel jack connector. In case you are unsure or your port is unable to handle the load DO NOT POPULATE the barrier diodes!

SD Drive ( the fancy )

Or a more integrated version, designed to power the SD card through an IEEE1284 compliant port.

Schematic diagram

Each channel is fed through a super low forward drop (0.31V) barrier diode to protect the port in case the push-pull outputs are operated by another software than the MS-DOS driver in this repository. The sum of the channels is buffered by a 100uF capacitor, and the supply voltage for the SD card is provided by a linear regulator. With the correct port type, this provides around 100mA on the 3.3V rail that can handle the microsecond long spikes that occur during flash write cycles.

Board layout

Double check that your port is IEEE1284 compliant. The circuit also provides an auxiliary power input through a USB-C connector. In case you are unsure or your port is unable to handle the load DO NOT POPULATE the barrier diodes!

Bill of materials

Part     Value          Package             Type

C1       1.0uF          0603-CAP
C2       1.0uF          0603-CAP
C3       0.1uF          0603-CAP
C4       0.1uF          0603-CAP
C5       100uF          PANASONIC_C
D1       CGRM4001-G     SOD-123_MINI-SMA   RB521ASA
D2       CGRM4001-G     SOD-123_MINI-SMA   RB521ASA
D3       CGRM4001-G     SOD-123_MINI-SMA   RB521ASA
D4       CGRM4001-G     SOD-123_MINI-SMA   RB521ASA
D5       CGRM4001-G     SOD-123_MINI-SMARB521ASA
J1       1-2295018-2    TE_1-2295018-2     USB-C
JP2      USD_CONNECTOR  MICRO-SD-SOCKET-PP 4UCON-15882
R1       100k           0603-RES
R2       100k           0603-RES
R3       100k           0603-RES
R4       100k           0603-RES
U1       IC1            SO14               TXB0104PWRSOIC14
U2       3.3V           SOT23-5            V_REG_AP2112K-3.3V
X1       SUB-D DB25     F25D

❗ This printed circuit board is yet to be tested. If you have built one, please let me know.

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MS-DOS Device Driver

Original device driver is written in 1994 by Dan Marks and it is based on TU58 by Robert Armstrong. Foolproof MMCv3/SDv1/SDv2 control module from Chan Fat FS has been added by profdc9 and posted on Vintage Computer Federation forum in 2014.

The driver is made available under the GNU General Public License version 2 and incorporates modified code from ELM Chan Fat FS: http://elm-chan.org/fsw/ff/00index_e.html.

Compilation

If you would like to compile the driver from source you'll need Borland C++ 3.1 with the included Turbo Assembler 3.1 installed on your DOS machine.

Binaries

💾 Download the latest pre-compiled version of SD.SYS

💾 Download a modified version compiled for Nilquader's NC100 SD adapter NILQUAD.SYS (MISO on BUSY)

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How to use it

• Create <=32MB partition(s) on a uSD card
• Format to FAT16 for best results
• Find out the port base of your parallel port
• Make sure that you are powering the adapter correctly
• Install the driver ⬆️ on DOS and enjoy. (see configuration below)

Prepare the card on Linux

1. Open a terminal
2. Find your block device with lsblk
3. sudo umount /dev/<device_partition> -- unmount if mounted
4. Partition with sudo fdisk /dev/<dev_name> -- or use gparted

• p lists, d deletes, n for new partition
• new partition --> p for primary
• enter last sector +32M
• t to change partition type to FAT16 (L to list avaiable formats )
• w to write changes to partition table

5. Format sudo mkdosfs -F 16 /dev/<dev_name>

Prepare the card on Windows

1. Open a command line and start diskpart
2. list disk -- find the disk number of your card
3. select disk # -- select your sd card
4. list part -- look for existing partitions
5. select part # -- select the partition to work with
6. delete part # -- to get rid of anything that is not FAT16
7. create part primary size=32 -- create a 32MB partition
8. exit -- leave diskpart
9. format X: /FS:FAT /Q -- format partition to FAT16 (replace X)

Source

Prepare the card on Mac

1. Open Terminal (Applications > Utilities)
2. hdiutil create -size 32m -fs "MS-DOS FAT16" -volname "MSDOS32MB" mydisk.dmg -- create a blank 32MB FAT16 disk image
3. hdiutil attach mydisk.dmg -- mount image
4. Copy your files
5. hdiutil detach /Volumes/MSDOS32MB -- unmout image
6. hdiutil convert mydisk.dmg -format UDTO -o mydisk.iso -- convert to raw format (mydisk.iso.cdr)
7. Use diskutil list to find your physical media
8. Unmount it if mounted diskutil unmountDisk /dev/disk#
9. sudo dd if=mydisk.iso.cdr of=/dev/rdisk2 bs=1m -- write your image to the partition
10. diskutil eject /dev/disk# -- eject card

DOS

Put the following line in your config.sys file in order to install and load the driver:

DEVICE=SD.SYS /p=<partition #> /b=<port base index>

/d = debugging mode (displays copious debugging messsages)
/k = use card detect signal to inform DOS that card is attached
/p = partition number (1-4) to partition in MBR to use.  Default: first available.
/b = port base index of parallel port, one of
     1=0x3BC, 2=0x378, 3=0x278, 4=0x3E8, 5=0x2E8
     Default: 0x378

Notes

You can have multiple copies of the driver loaded if there are multiple partitions on your SD card you want to use simultaneously.

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