Electroknit Serial Connections
Connecting to Brother Knitting Machines
The external Disk Drive Connection
Some models of knitting machine interface with an external floppy disk drive. By using this interface with the knitting machine, we can save and restore patterns from the machine.
The interface is a serial data connection at 9600 bits per second, with flow control signals, but the signal voltages are not RS-232 standard.
Connector Pinout for the knitting machine and external floppy drive
The connectors on both the knitting machine and external disk are 8-pin keyed 2x8 headers with pins on on 0.1 inch centers The knitting machine and external disk drive are connected.
In this photo, there is a dot near pin one.
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.
|Knitting Machine Connections|
|Knitting Machine||Floppy Drive|
|Pin||KM Signal||KM I/O||FD I/O||FD Signal||Notes|
|2||RTS||Out -->||--> In||CTS||Inside KM tied to 5(DTR), Pulled up through 1K resistor|
|3||CTS||In <--||<-- Out||DTR|
|4||No Connection||<-- Out||DTR|
|5||DTR||Out -->||--> In||DSR||Inside KM tied to 2|
|6||RXD||In <--||<-- Out||TXD|
|7||TXD||Out -->||--> In||RXD|
|8||RTS||Out -->||No Connection||In KM Follows state of Pin 3 (buffered)|
Signals are (essentially) all 5V logic level. The signals from the knitting machine are slightly higher, since they are generated by CMOS logic, but the external disk drive has resistor padding which can handle this. The disk drive outputs 5V TTL logoc levels. Inputs on the disk drive will accept standard TTL logic output levels, but will not accept the entire normal TTL input specified range, due to the input padding.
Basically, you should use 5V logic levels to connect to the knitting machine and disk drive, and it'll work fine.
Interfacing to the knitting machine
The easiest and perhaps least expensive way to connect a computer to the knitting machine is to use the [FTDI Friend from Adafruit]
In order to do that, you need to reprogram the device and make one jumper change on it. Unfortunately, the [FT_PROG tool for programming it] only runs on windows.
Use the FT_PROG tool to invert all signals on the device.
Then you need to change the signal logic level to +5 Volts. To do this, cut the default jumper on the bottom of the FTDI Friend and solder the jumper for +5V.
Connect the knitting machine and the FTDI friend pins like this:
NOTE: This should be correct, but I have not yet double checked it. I'll update this page soon when I do
|FTDI Friend to Knitting Machine Connections|
|KM Pin||FTDIF Pin|