history.txt

// BACKGROUND:
// When I first received an ultrasonic sensor I was not happy with how poorly
// it worked. Quickly I realized the problem wasn't the sensor, it was the
// available ping and ultrasonic libraries causing the problem. The NewPing
// library totally fixes these problems, adds many new features, and breaths
// new life into these very affordable distance sensors. 
//
// FEATURES:
// * Works with many different ultrasonic sensor models: SR04, SRF05, SRF06, DYP-ME007 & Parallax PING))).
// * Interface with all but the SRF06 sensor using only one Arduino pin.
// * Doesn't lag for a full second if no ping/echo is received.
// * Ping sensors consistently and reliably at up to 30 times per second.
// * Timer interrupt method for event-driven sketches.
// * Built-in digital filter method ping_median() for easy error correction.
// * Uses port registers for a faster pin interface and smaller code size.
// * Allows you to set a maximum distance where pings beyond that distance are read as no ping "clear".
// * Ease of using multiple sensors (example sketch with 15 sensors).
// * More accurate distance calculation (cm, inches & uS).
// * Doesn't use pulseIn, which is slow and gives incorrect results with some ultrasonic sensor models.
// * Actively developed with features being added and bugs/issues addressed.

// HISTORY:
// 08/15/2012 v1.5 - Added ping_median() method which does a user specified
//   number of pings (default=5) and returns the median ping in microseconds
//   (out of range pings ignored). This is a very effective digital filter.
//   Optimized for smaller compiled size (even smaller than skteches that
//   don't use a library).
//
// 07/14/2012 v1.4 - Added support for the Parallax PING)))™ sensor. Interface
//   with all but the SRF06 sensor using only one Arduino pin. You can also
//   interface with the SRF06 using one pin if you install a 0.1uf capacitor
//   on the trigger and echo pins of the sensor then tie the trigger pin to
//   the Arduino pin (doesn't work with Teensy). To use the same Arduino pin
//   for trigger and echo, specify the same pin for both values. Various bug
//   fixes.
//
// 06/08/2012 v1.3 - Big feature addition, event-driven ping! Uses Timer2
//   interrupt, so be mindful of PWM or timing conflicts messing with Timer2
//   may cause (namely PWM on pins 3 & 11 on Arduino, PWM on pins 9 and 10 on
//   Mega, and Tone library). Simple to use timer interrupt functions you can
//   use in your sketches totaly unrelated to ultrasonic sensors (don't use if
//   you're also using NewPing's ping_timer because both use Timer2 interrupts).
//   Loop counting ping method deleted in favor of timing ping method after
//   inconsistant results kept surfacing with the loop timing ping method.
//   Conversion to cm and inches now rounds to the nearest cm or inch. Code
//   optimized to save program space and fixed a couple minor bugs here and
//   there. Many new comments added as well as line spacing to group code
//   sections for better source readability.
//
// 05/25/2012 v1.2 - Lots of code clean-up thanks to Adruino Forum members.
//   Rebuilt the ping timing code from scratch, ditched the pulseIn code as it
//   doesn't give correct results (at least with ping sensors). The NewPing
//   library is now VERY accurate and the code was simplified as a bonus.
//   Smaller and faster code as well. Fixed some issues with very close ping
//   results when converting to inches. All functions now return 0 only when
//   there's no ping echo (out of range) and a positive value for a successful
//   ping. This can effectively be used to detect if something is out of range
//   or in-range and at what distance. Now compatible with Arduino 0023.
//
// 05/16/2012 v1.1 - Changed all I/O functions to use low-level port registers
//   for ultra-fast and lean code (saves from 174 to 394 bytes). Tested on both
//   the Arduino Uno and Teensy 2.0 but should work on all Arduino-based
//   platforms because it calls standard functions to retrieve port registers
//   and bit masks. Also made a couple minor fixes to defines.
//
// 05/15/2012 v1.0 - Initial release.
// ---------------------------------------------------------------------------