Import the unmodified SDPP source.

From https://forum.vcfed.org/index.php?threads/sd-card-to-parallel-port-driver-for-msdos-ver-1-1.42008/.

XTMax/Apps/SDPP/README.TXT

@@ -0,0 +1,72 @@
+
+SD card driver for parallel port
+
+I wrote this to simplify data transfer between my IBM PC and my laptop, because my laptop does
+not have a 360k floppy drive but does have an SD card slot.
+
+WARNING:  I take **no responsibility** for any damage to your computer, parallel port, or SD
+card, or any data.  You use this driver at your own risk.   It is highly recommended you use
+an expendable parallel port card with your expendable SD card, and your expendable data.
+It is recommended that you use a level converter IC with between your 5 volt parallel port
+outputs and the SD card 3.3 volt inputs.  This project is intended as a fun hack for hobbyists
+and enthusiasts and not for serious work.
+
+This driver is made available under the GNU General Public License version 2.  It incorporates
+modified code from ELM Chan Fat FS (http://elm-chan.org/fsw/ff/00index_e.html).
+
+Usage:
+
+In your config.sys file
+
+DEVICE=SD.SYS /d /k /p=<partition #> /b=<port base index>
+
+Loads and installs the SD card driver.
+
+/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
+
+For best results, format your SD card with a FAT16 partition which is less than 32 MB in size.
+NOTE:  Many versions of DOS don't know how to handle FAT32, and many can't have FAT16 with a 
+partition size greater than 32 MB.  Therefore, if you want to play with this, make your parition on
+the card FAT16 and less than 32 MB.  This assures the best compatibility.  You can have multiple copies of the 
+driver loaded if there are multiple partitions on your SD card you want to use simultaneously.
+     
+I have used Adafruit's microSD adapter
+ (http://www.adafruit.com/products/254?gclid=CLH7l4iEkrwCFQPNOgod7BkAQA)
+if you want a relatively simple way to interface your PC parallel port to 
+the SD card.  The adapter provides the 3.3 volts needed to power the SD card, as well
+as a the level shifting between the 5 volt parallel port output and the 3.3 volt input.
+If you directly connect a 5 volt output to a 3.3 volt input, you risk latching up the
+3.3 volt input and damaging the card or computer from exceesive current.
+Some have used series resistors instead of the level converters, but I found this
+to not be that reliable and still may have this problem.  Also, some SD cards MISO/DO
+outputs are unable to drive a TTL input of some parallel ports, so you may need to add
+a buffer between the two as well.  I have found quite a bit of variability in the drive
+current required for the inputs of various parallel ports.
+
+The driver uses the very slow serial peripheral interface (SPI) mode of the SD card.  The
+speed, which depends on your PC speed, could be as slow as 10 kilobytes/second.  This is 
+not a replacement for your hard drive.  Your parallel port should be configured for standard
+mode (not bidirectional) if applicable.
+
+The connections between the parallel port and the SD card are as follows:
+
+Parallel port          SD card
+
+PIN 25 signal GND      GND (Vss)
++3.3V                  Vdd (power)
+PIN 2 signal D0        CMD / MOSI / DI (SPI data in)
+PIN 3 signal D1        SCLK / CLK (SPI clock)
+PIN 4 signal D2        DAT3 / CS (SPI chip select)
+PIN 13 signal SELECT   DAT0 / MISO / DO (SPI data out)
+PIN 11 signal BUSY     Card detect (if you SD card slot has one)
+
+For similar setups, look up parallel port to JTAG adapters which are used for in circuit
+programming and debugging.
+
+Good luck and be careful!
+