Electroknit Technical Information
From Antitronics
Brother Electroknit KH-930E Technical information
Source Code Repository
The latest source code and documents for this project may be found here:
https://github.com/adafruit/knitting_machine
Disk Drive/Computer Connection Notes
The external floppy drive for this machine was the same as a Tandy PDD1 (Portable Disk Drive 1). This drive is connected using a serial port. There is documentation on the internet about how to connect these drives to computers, but the connector pinout on the knitting machine is different than the drive, and I didn't find that documentation to be helpful.
I was able to figure out the connector pinout by examining the knitting machine PCB.
Knitting Machine/Computer Connection Notes
The knitting machine drive connection uses CMOS voltage levels, not RS-232.
Here is the pinout of the drive connector on the knitting machine:
_____
| |
______|___|______
| | | | |
| 7 | 5 | 3 | 1 |
|___|___|___|___|
| | | | |
| 8 | 6 | 4 | 2 |
|___|___|___|___|
The pin numbering is shown as they are labeled on the knitting machine PCB, and does not agree with other documents I found on the web.
| Connector Pinout | |||
| Pin | Signal | I/O | Notes |
|---|---|---|---|
| 1 | Ground | ||
| 2 | Out | Tied to 5, Pulled up through 1K resistor | |
| 3 | CTS? | In | (Tie to pin 2) |
| 4 | No Connection | ||
| 5 | Out | Tied to 2, Pulled up through 1K resistor | |
| 6 | RXD | In | |
| 7 | TXD | Out | |
| 8 | RTS? | Out | Follows state of Pin 3 (buffered) |
Methods of connecting the knitting machine to a computer
Using a USB serial adapter WITH flow control
This is a method I have used extensively with one model of knitting machine, but I no longer recommend it. Although it does not require any additional hardware like a FTDI adapter, this method does not present the exact same voltage levels to the knitting machine as the external drives which were designed to work with the machine. Although I have not had any reports of problems, it is possible that this method could stress the knitting machine input circuitry, and therefore I think it is safest not to use it.
| Cable connections with flow control | |
| Knitter | 9 pin connector |
|---|---|
| 1 | 5 |
| 6 | 3 |
| 7 | 2 |
| 8 | 4 |
Using a USB serial adapter WITHOUT flow control
I have pulled pin 3 high, and am not using flow control in my software. I have not had problems with data loss while sending to the knitting machine, and the machine I am using is fast enough to always keep up with data received from the knitting machine. The data rate is 9600 bps, and the largest amount of data sent at once is 1024 bytes.
Here is the cable I am using to connect the knitter with a USB 9 pin serial port:
| Cable connections without flow control | |
| Knitter | 9 pin connector |
|---|---|
| 1 | 5 |
| 2 tie to 3 | |
| 6 | 3 |
| 7 | 2 |
Using a FTDI serial adapter cable (RECOMMENDED)
Using an FTDI adapter is the best way to assure that you are interfacing with the machine using the same signal voltages as the original external floppy drives. I will update the description in this section very soon, when I have tested and documented building an interface with adafruit's "FTDI Friend".
Until then, what follows is an older description of this method:
The knitting machine uses 5V Logic level signals on the serial port. I have successfully used a FTDI USB to 5V serial adapter cable to communicate with the knitting machine. I had to invert the TXD and RXD signals, but it's possible to reprogram the serial adapter to invert those signals.
The adapter I used is the FTDI TTL-232R-5V, which is available from Mouser electronics here: FTDI Adapter. The FTDI MProg utility to reprogram the adapter can be found here.
MProg only runs under windows.
Software Interface Information
There are a number of documents on the web about the Tandy PDD1 and the serial API for it, Most of them are incomplete. The knitter places the drive into a mode called "FDC emulation Mode", which allows access to raw sectors. This document is the most complete documentation I was able to find:
External Disk Drive Emulator
I have written software that emulates the external disk. It runs under Linux and keeps the data as files on the linux file system. This allows knitting designs to be saved and restored using the emulation computer. I am using these files to reverse-engineer the knitting machine file format.
The emulator is written in Python, and released under the GPL. It has been tested most extensively under Ubuntu Linux. I have reports that it does not work on windows due to problems with the serial library. It has been successfully run under OSX. If you have any information to add about platforms that it does or doesn't work on, let me know and I will update this information
I am happy to work with people who are trying to use the emulator with different models of knitting machine, and hoep to improve compatibility with other machines.
The source code is available in the git repository listed above.
Software for manipulating Brother data files
I have begun a python class which will provide an API to the brother data files.
Source code is in the git repo.
Knitting Machine File Format
A lot of the file format is now understood. Documentation is in the git repo.
Work on this continues.
This work was greatly helped by prior work performed by John R. Hogerhuis and posted on the kminternals yahoo group.
Related Links and Documents
Your mileage may vary.
BL5 Brotherlink 5 serial or USB cable Brotherlink information
Yahoo group dedicated to hacking brother machines
Brother Liberation Front is working on open source interfaces
Info and protocols for the FB-100 interface
KE-100 motor drive (not sure that this is the right model drive for the KH-930E)
