12 November 2020

PFAFF 7570/1475CD Serial Cable for the 21st century.

The victim resting in its natural habitat.

My mother wanted to be able to update some of the stitches on her PFAFF 1475CD using her PC. As the process of programming on the machine itself is tedious and does not lend it self to corrections. I had two problems to solve off the bat. First the cable is a D-Sub 25pin Serial RS232. No computer in the last 20 years has been made with this connector.

"Made for PFAFF in West Germany"
I had a DB25 to DB9 adapter, but modern computers, laptops even more so, don't have 9 pin serial ports... So i grab a USB to serial adapter. Unfortunately the manufacture, Prolific, intentionally didn't support Windows 7 or 10. bummer. 

DB25/DB9 adapter

I found in an old "Random Electronics Junk Box" a Keyspan serial adapter. Great! the Drivers work with Windows 10, ComPort33. OK but what about the software?

Keyspan serial USB adapter.

The software is from 1990. Meaning MSDOS. Well i happen to be a vintage video game enthusiast and run many old dos games using the wonderful DOSBOX program. But could it handle a physical serial port? The manual, you guys/gals read the manual don't you? The manual says YES!

Cool! so following some configuration and more near swearing than I'd like to admit... 

I was able to read to contents of the machine's memory using the PFAFF Creative Designer software from within DOSBOX using the many adapters to talk to the machine. The solutions was ugly and unwieldy. It risked being broken. 

Big ugly complex fragile cable.
So I searched for a better solution. Enter Limor "Ladyada" Fried and her crew at Adafruit Industries. They make a cable that will work perfectly for this application and it's low cost. USB to TTL Serial Cable.

All I need now is a connector for the PFAFF 1475CD machine, a 7pin DIN. Thanks Amazon! http://amzn.com/B07XCSX3JP

With a two part count and my soldering iron I'm ready to improve the situation!

A clean a elegant solution. Isn't that neater?

PC-Designer Software V1.3 (c) 1991 running in DOSBOX
Now for a bit more background and the technical details of how I pulled it off:

The original PFAFF cable (made in West Germany by the way) was a DB25 to 7 pin DIN connector. Inside the D shaped 25pin connector (DB25) is a circuit, depicted far below, that converts and inverts RS232, 25 Volt Direct Current differential signal to 5vdc TTL signal. PFAFF used a 5vdc supply from the machine to power and reference this circuit. We won't need the circuit as the TTL-USB adapter makes the circuit unnecessary. 

We won't be using PFAFF +5v supply and will leave the pin unconnected. The TTL-USB adapter has a +5v supply as well. I used heat shrink to cap it off safely as we won't be using it either. 

Red +5vdc -/- no connection
PFAFF +5vdc DIN7 Pin 3 -/- no connection

Now we connect a common signal reference and grounding wire (GND, black, to pin 4 on the DIN7 connector).
Black gnd -- DIN pin 4

Connect the TTL-USB Transmit to PFAFF receive and vise versa:
Green tx -> DIN pin 1
White rx <- DIN pin 7

Adafruit TTL-USB -- DIN7 connector summary:
Green tx -> DIN pin 1
White rx <- DIN pin 7
Black gnd -- DIN pin 4
Red +5vdc -/- no connection

My USB-TTL to DIN7 pin out

Ok, I know my soldering isn't pretty in these images. I did it quick. After testing and confirming everything works, I redid this and used matching color heat shrink.

TTL adapter soldered to DIN7 connector

TTL adapter soldered to DIN7 connector

Inside the adafruit USB-TTL adaptor

Thanks to Rudolf of achatina.de . They depict the circuit in the DB25 (the black rectangular connector).
Rudolf's pinout diagram of the PFAFF serial cable.

Original: Standard 232 (DB9/DB25) Pin -- PFAFF 7pin DIN connector
PC TX serial pin 3 -> brown PFAFF RX (pin 1)
PC RX serial pin 2 <- yellow PFAFF TX (pin 7)
Ground serial pin 7 -- green gnd (pin 4)
No connection* -/- white vcc (pin 3)

*while the PFAFF white (DIN7 pin3) does not have a pinout on the DB25, it does supply power and a voltage reference to the circuit housed in the DB25 connector.
This circuit converts and inverts RS232 signal to TTL signal.
Rudolf's circuit diagram of the original PFAFF serial cable.
DOSBOX conf (windows, you may have to adjust the com-port number):
serial1=directserial realport:COM33
DOSBOX conf (linux/mac, you may have to adjust the USB tty number):
serial1=directserial realport:ttyUSB
DOSBOX conf (all systems)
#mount c ~/dos/PFAFF
mount c c:\users\USER\PFAFF\

for the software create a PFAFF directory (case sensitive) and copy the PCD program files to it. adjust the [autoexec] section of dosbox.conf to mount the PFAFF directory. upon running dosbox the PCD program should automatically launch.



Thanks to: 


  1. Thank you soo much for sharing this! Quick note: The linked zip file in your Google drive is shown as "in the users trash" and can't be accessed.
    Again, thank you!

  2. This detailed DIY description to shift my wife's machine into actual computing environment is the thing I've been two years looking for! Thanks a lot for putting it on the web! I'll try it out at the very next opportunity.

  3. i am trying with pfaff windows software designer. nothing yet..

  4. I have got designer ver 2.2 windows xp working with your cable.

  5. Hi Gents, I did the cable accoridng to the SOP, but when I'm trying to connect it with PC-designer ther is a sound from the machine and a pop-up: No communication with the machine. Please check all the connections. Is there any specyfic setting on the virtual port (transfer rate ect) which should I set up?

    1. I'd be happy to help you diagnose. Send me descriptions of what you've tried, copies of your configuration files, and pictures of the cable pins. I'll also need to know what your dosbos host is.

  6. Hi, I'm sharing a link to my google catalog with photos. I solder the cable exactly according to the pinout attached in the post. I tried both - with DOS version and DOSBOX and Windows 2000 and PC-Designer 2.2. In both cases, machine is blinking for a while, and then " no conection pop-up". I order new usb-to-ttl tool to check if this is not propper. then, I will check the socket in the machine. I don't have any other ideas yet.

    1. Windows 2000 would need the proper drivers installed for the ttl-usb adapter. I don't have a copy of W2K to test with. Double check that you have the necessary drivers installed, if they even exist. For windows and dosbox the comport speed and parity should be set to automatic. No need to specify in the driver. The PFAFF pcd sets the speed for the port when running the application within dosbox.

    2. Hi, did you order the adapter directly from China by any chance? I did the same and it looked a lot like your's. I had no luck with it. From what I've read, these chips are often bootlegged - that there are no numbers printed onto the chip might be a sign of that.
      I then ordered the following adapter in Europe and it worked: https://www.reichelt.at/at/de/raspberry-pi-usb-zu-ttl-0-9-m-pl2303hx-rpi-usb-ttl-p150567.html?r=1

    3. No. I got my adapter from a North American retailer, adafruit.

      A chip with no markings is almost certainly counterfeit. Try using a known good unit.

    4. I have the same problem. I tried several usb-to-ttls and checked the machine socket. Did you find a solution?

  7. Ah, sorry, I intended my reply for belweder87, but I guess it doesn't work that way in Blogger :)

    1. Apologies. You do make a great point however. Glad to hear yours is working! I'm always a bit surprised when this post gets attention. 😃

  8. Heeyyyyy boy am I glad I found this page!! I have the 7570 with the cable; I even have access to an old-ass PC that was purchased for that purpose. BUT, I'd much rather use my laptop. SO, my questions are... if I go through this process to make the adapter, what does the PCD software even look like now? How usable is it, what can you really do? Can you load in more fonts? More designs? I would love any weigh-ins from anyone who has successfully done this! What was the final result?? Thank yooouuuu!!!!