ParallelPrinter/README.md

[![Arduino CI](https://github.com/RobTillaart/ParallelPrinter/workflows/Arduino%20CI/badge.svg)](https://github.com/marketplace/actions/arduino_ci)
[![Arduino-lint](https://github.com/RobTillaart/ParallelPrinter/actions/workflows/arduino-lint.yml/badge.svg)](https://github.com/RobTillaart/ParallelPrinter/actions/workflows/arduino-lint.yml)
[![JSON check](https://github.com/RobTillaart/ParallelPrinter/actions/workflows/jsoncheck.yml/badge.svg)](https://github.com/RobTillaart/ParallelPrinter/actions/workflows/jsoncheck.yml)
[![License: MIT](https://img.shields.io/badge/license-MIT-green.svg)](https://github.com/RobTillaart/ParallelPrinter/blob/master/LICENSE)
[![GitHub release](https://img.shields.io/github/release/RobTillaart/ParallelPrinter.svg?maxAge=3600)](https://github.com/RobTillaart/ParallelPrinter/releases)


# ParallelPrinter

Arduino library that implements a parallel printer (driver) - implements the PRINT interface.


## Description

This library defines a parallel printer object.

It implements the **Print interface** to be able to print all data types 
using **write()**, **print()** and **println()**.
The printer writes every byte over 8 parallel lines including a **STROBE** (clock) pulse,
while waiting for the connected printer not to be **BUSY** or **OUT OF PAPER** (OOP).

This library is meant to be a starting point to make a "printer driver" for a 
specific parallel printer. These can often be bought in 2nd hand stores or so.

Have fun!

**Note:** This lib is a extended redo of the ParPrinter class.


## Interface

### Constructor

- **ParallelPrinter()** uses default pins (13, 2, 12, \[3,4,5,6,7,8,9,10\])
- **ParallelPrinter(uint8_t strobe, uint8_t busy, uint8_t oop, uint8_t \*arr)** 
define 3 control pins + 8 data pins (= arr\[8\]).
- **void begin(uint8_t lineLength, uint8_t pageLength)** set line and page length parameters


### Print interface

- **size_t write(uint8_t c)** send a single byte to printer, implements Print interface. 
Therefore all **print()** and **println()** functions will work.
- **void formfeed()** to eject current page or forced go to the next page.
- **void linefeed()** send a linefeed. 
The number of actual lines is set by **setLineFeed()**


### Configuration

These settings are pretty straightforward.

- **void setLineLength(uint8_t lineLength)** idem
- **uint8_t getLineLength()** returns the current line length. 
- **void setPageLength(uint8_t pageLength)** idem
- **uint8_t getPageLength()** returns the current page length.
- **uint8_t getLineNumber()** returns current line number.
- **uint8_t getPageNumber()** returns current page number.
- **uint8_t getPosition()** returns the position on a line.
- **uint8_t setTabSize(uint8_t tabsize)** tabs are replaced by spaces. n can be 0 or any size!
- **uint8_t getTabSize()** returns tabSize set
- **void setLineFeed(uint8_t lineFeeds)** lineFeeds = 1,2,3  1 = default. 
- **uint8_t getLineFeed()** returns lineFeeds set
- **void printLineNr(bool b)** can be set to true, false.


### Expert mode

- **bool isOutOfPaper()** to check paper tray before printing starts.
- **void setStrobeDelay(uint16_t n = 2000)** allows tuning of performance. 
Make the strobe pulse shorter == faster printing (printer dependant).
Default value = 2000. Time in microseconds.
- **uint16_t getStrobeDelay()** returns value set.

**Note** mechanical printers e.g. dot matrix, really do need a way to stop receiving 
data as they do not have large buffers.


## See also

https://en.wikipedia.org/wiki/Parallel_port#Centronics


## Future

- update documentation
- extend unit tests?
- test more.
- extend simulator sketch.
  - Make a front end of a parallel printer, 
  - Accepts the clocked bytes and print them e.g. over serial.
- derive e.g. an HP or an EPSON printer from this class.
  - special modes e.g. bold italic underline.
- **write(uint8_t \* buf, uint8_t length)** should be added
  - might not really add to performance..
- fix blocking TODO in sendByte
  


## Operation

See examples.