An Introduction to ATLAS Pixel Detector DAQ and Calibration Software Based on a Year's Work at CERN for the Upgrade from 8 to 13 TeV

An overview is presented of the ATLAS pixel detector Data Acquisition (DAQ) system obtained by the author during a year-long opportunity to work on calibration software for the 2015-16 Layer‑2 upgrade. It is hoped the document will function more generally as an easy entry point for future work on ATLAS pixel detector calibration systems. To begin with, the overall place of ATLAS pixel DAQ within the CERN Large Hadron Collider (LHC), the purpose of the Layer-2 upgrade and the fundamentals of pixel calibration are outlined. This is followed by a brief look at the high level structure and key features of the calibration software. The paper concludes by discussing some difficulties encountered in the upgrade project and how these led to unforeseen alternative enhancements, such as development of calibration "simulation" software allowing the soundness of the ongoing upgrade work to be verified while not all of the actual readout hardware was available for the most comprehensive testing.