Apple ImageWriter emulation

[RWAP]

Another emulator we have been working in recently emulates the Apple ImageWriter printer. We are having to make a few assumptions here about its workings as there is different information in different manuals.

The main issues we have come across is the operation of vertical tabs and whether any of the higher character codes allow for ASCII text on an inverted background.

The vertical tabs are peculiar (typical Apple) in that you appear to specify what tabs appear on each printed line but the tabs apply to 5 pages of a document each page able to have different tabs! It is unclear what happens on page 6 but possibly that was because the original apple pc could only print a maximum of 5 pages. Vertical tabs don't even get a mention in the programmer's manual for the ImageWriter II

[RWAP]

We think that we have finally understood the implementation of vertical tabs - which helps, so the Apple ImageWriter emulator is now ready for testing. The vertical tabs are actually similar to the ESC/P2 vFU channel implementation where you can have 5 different sets of tabs and you decide which set you use when you call a tab.

The original printer connected via serial port to the Apple computers, so if you have a suitable serial to USB convertor, you can use a special serial port implementation in the Retro-Printer software to turn a Raspberry Pi into an Apple Imagewriter