Vintage computing enthusiast Fred Jan Kraan has designed a serial adapter for what is, today, something of a rare sight: a classic tape punch machine.
“The converter project is intended for the Facit Type 4070 Code 0001 Paper Tape Punch. This early 4070 is based on 6V DTL [Diode-Transistor Logic] logic and only has a parallel interface,” Kraan explains of the project. “By interfacing an Arduino Nano [compatible microcontroller] to the parallel connector (with proper level conversion) a serial interface is added. The board is powered by the 4070.”
An Arduino Nano-compatible microcontroller drives this DTL parallel to RS232 serial adapter for a vintage Facit 4070 tape punch. (đź“·: Fred Jan Kraan)
Released in the late 1960s, the Facit 4070 was designed as the write portion of a paper tape read-write system — designed for improved portability and, arguably, reliability than the punch-card system that had preceded it, itself inspired by the operation of the programmable Jacquard loom. Programs were punched as holes into a roll of paper tape, which could then be read back by a tape reader typically connected to a TeleType terminal.
As you might expect from a piece of 1960s technology, though, the Facit 4070 doesn’t come with a handy USB port — and even its native data connection is a sign of the times, being a parallel port using the elevated voltage of a Diode-Transistor Logic (DTL) system rather than the Transistor-Transistor Logic (TTL) common today. That’s where Kraan’s adapter comes in: converting that parallel DTL interface into an RS232 serial connection.
The tape punch is in excellent condition, and with its new serial port adapter should start storing data again. (đź“·: Fred Jan Kraan)
“The project-board interfaces all signals of the 4070, but only a small subset is used in the first firmware,” Kraan explains. “Data can only transferred at 600 Baud, which is slower than the 4070 punch speed. This means no handshake needs to be implemented. The Arduino console is only used for testing, but can potentially (also) be used for data transfer.”
Source code and KiCad design files for the project, which were recently updated to work around a few errata in the original release, are available on Hackaday.io under an unspecified license.