41 lines
2.1 KiB
Plaintext
41 lines
2.1 KiB
Plaintext
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MicroCore Labs - Arduino Leonards-based IBM Wheelwriter Printer Option
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Description:
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This is an Arduino Software project which allows RS232 access to an IBM Wheelwriter Typewriter.
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Using a terminal running at 300 baud (300,n,8,1), the user can directly send characters to the typewriter.
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They can also cut and paste long documents into the terminal, which will be printed by the typewriter.
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It has been tested on an IBM Wheelwriter 5, however other IBM typewriters such as the Wheelwriter 3 and 6 may also work.
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The only connection needed to the typewriter is via two pins within the access panel at the top rear of the typewriter.
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I am using an Arduino Leonardo board which uses the ATmega32u4 microcontroller which contains two UART controllers.
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This design uses both UARTS. One is connected to the host at 300,N,8,1 and the second connects to the IBM Wheelwriter's IBM_BUS
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interface which runs at 188k, N,9,1. The UART is used in a non-standard 9 databits operation which is not directly supported
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by the Arduino software base. I needed to directly write a few registers to active this mode.
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The IBM_BUS is bi-directional, so the Arduino's UART Transmitter must be deactivated and set to hi-Z so it will not conflict
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with the drivers contained in the typewriter. To save time I simply added a delay to give the typewriter time to ACK on the IBM_BUS
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rather than sample it for the ACK response. Faster printing action could be achieved if a separate bus transceiver was used
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to switch on and off between the Arduino and the typewriter driving the bus.
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There is very limited buffering in the Arduino's UART transmitter and reciever and I have also provided very shallow buffering,
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so characters must be sent from the host at the pace typical of typing on the typewriter by hand.
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Pinout
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- The IBM Wheelwriter pins of interest are: 4=GND and 5=IBM_BUS. Pin#1 is on the left when looking at the typewriter from the front.
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- On the Arduino, only the UART TX pin-1 and GND are needed.
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