Hack, Make, Teach
Lately I’ve been working on the knitting machine code some more. First, the thing that will affect fellow hackers and knitters the most -
Update 3/1/12: After some more thought, I’m recommending against simply using a serial adapter, as I had previously written here. My reasoning is this -
While I’d like to make it as easy as possible for people to connect to their knitting machines, I’ve only tested this on one model of machine. A standard USB serial module may present voltages to the knitting machine which are outside the range that the external drives do. While I’ve determined that this is probably safe for the one model of knitting machine that I have, I can’t be sure that it’s not going to stress the input circuitry on some models. The absolute safest way to do this is to use the exact same signal voltages that the external disk drive does. In order to do this, using an FTDI interface is the best way. The cost for using adafruit’s “FTDI Friend” is only about $5 more than using a standard serial interface, and since these old knitting machines are irreplaceable and often very expensive when you can find them, I’d rather do this the absolute safest way. I have no reports of problems from using regular serial interfaces, but I think that this is a case where absolutely correct engineering is more appropriate than a hack to save a few dollars.
I’ll be updating the wiki page very soon with directions for how to use the FTDI Friend to interface with the knitting machine.
I’ve now thoroughly tested connecting a PC to the knitting machine using only a standard USB serial adapter. This means that you don’t have to fool with FTDI interfaces, inverting signals, etc. All it takes is a serial adapter, a female DB-9 connector, and four jumper wires. That’s documented on the wiki page.
This makes it much easier for the less technical among us to connect their machine to a computer.
The rest will have more impact in the long run . . .
I’ve obtained an actual Brother FB100 external floppy drive, and successfully connected it through a serial adapter. It requires a 5V adapter – I’m using the adafruit FTDI friend. It’s a little complex – you have to rejumper and reprogram the FTDI friend. That’s also documented on the wiki page here.
There are some files currently in the ‘experimental’ directory in the source repo which communicate with the disk drive, and extract information from knitting machine disks into the format used by my disk emulator. I’m planning to use these to help fill in some gaps in knowledge about the file format used by the knitting machine.
Most people won’t have use for this code to interface with the floppy drive, as the drives are rare.
I have other plans for this investigation, so I may have more to say about it soon.