Knit and Sew

DesignaKnit & Silver Reed

  The Silver Reed story told by a technician.

Silverrreed knitting machines have always been a special breed. They are different. The most interesting difference is the feature that Silver Reed knitting machines use a different method for knitting a pattern. There are two way to knit a pattern: mechanically using punch cards or electronically. The latter is where Silver Reed knitting machines are different: they have electronics in the carriage.

Long time ago, Soft Byte developed interfaces (cables with electronics inside) to communicate directly with the carriage. The Silverlink 2 is the best-known interface. The Silverlink2 is hooked up to the serial port and the other end of the Silverlink 2 is directly connected to the carriage via the curly wire.

"What is the problem with that?" you might ask yourself. The end result is rather clear: the pattern shifts sometimes one or more stitches without apparent reason and your garment is ruined, to say the least, if you don't see the pattern shift straight away.

Next question: How come?
I will try to explain in a popular scientific way how a Silver Reed knitting machine works. In the back of the needle bed you find a black strip with holes on equal distance. The distance between the holes is the distance between the needles. The carriage contains electronics that can find out whether the carriage is above a hole or not. One of the signal lines in the carriage means "above hole". It is clear that the control logic for the carriage has to react when the "above hole" signal gets asserted. When the carriage moves above a hole, the control logic needs to inform the carriage whether the corresponding needle has to be selected or not. This information is passed via the serial port of the PC. The "above hole" signal is an input signal for the PC; the "select needle" is an output signal. During interactive knitting, DesignaKnit pays close attention to the "above hole" signal and when it occurs, DesignaKnit will return as soon as possible the value of the "select needle" signal.
At the time the Silverlink 1 and 2 were developed, DesignaKnit ran under DOS and later under Windows 3.xx. All processor time was available to DesignaKnit to monitor the "above hole" signal and all worked as planned. Microsoft went on and developed Windows NT, 2000, XP and also Windows 95, 98 and ME. There was also new development in the hardware area and new features like power management were invented. The power management features can work without intervention of Windows and are supported by some BIOS versions. The net effect is that there is less processor time available for DesignaKnit to monitor the "above hole" signal despite processors becoming quicker and quicker. Also, Windows has its own opinion about what is important to do. This is not necessarily running DesignaKnit! You can see the problem already coming: at a certain moment Windows figured that there was something more important to do that running DesignaKnit like start a screen save and the painting of the associated beautiful picture. In the meantime, the carriage has given out two or more times the "above hole" signal. DesignaKnit however didn't notice. This causes the pattern to shift.

The more recent versions of DesignaKnit have facilities to obtain as much processor power as possible. This is only possible on Windows NT, 2000 and XP. The facilities make the problem more or less disappear, but it cannot be guaranteed. October 2001 it became apparent that something drastic needed to be done. It was decided to develop a new Silverlink 4 that would fix all currently known problems for all known PC's. The new Silverlink 4 has its own processor. This avoids the problem that Windows wants to use the processor too. The processor in the Silverlink 4 has all time available to monitor the "above hole" signal. DesignaKnit now only has to provide the right commands like "knit row x".
The problem of DesignaKnit users who have a computer without serial port is fixed too: The Silverlink 4 has both a serial and a USB port.


Last Modification: Jul 31, 2010 (c) Copyright 2000-2010, Jos Timmermans