diff --git a/20191212/hp-20191212.tex b/20191212/hp-20191212.tex
index a44fb1c291aa53c0dec848b17f53ee903a2a4b2c..92d6c381cc9629cb6ca5b64a1ae0a1485f032ec9 100644
--- a/20191212/hp-20191212.tex
+++ b/20191212/hp-20191212.tex
@@ -20,7 +20,7 @@
% Attribution-ShareAlike 3.0 Unported License along with this
% document. If not, see <http://creativecommons.org/licenses/>.
-% README: make, Byte-Reihenfolge - Endianness, Binärdarstellung negativer Zahlen, Speicherausrichtung - Alignment
+% README: make, Byte-Reihenfolge - Endianness
\documentclass[10pt,t]{beamer}
diff --git a/20191212/pgscript.sty b/20191212/pgscript.sty
deleted file mode 100644
index 0a36e84e6b3087a3369e74d1a5b33fd58902993d..0000000000000000000000000000000000000000
--- a/20191212/pgscript.sty
+++ /dev/null
@@ -1,137 +0,0 @@
-% pgscript.sty - LaTeX Settings for Lecture Notes
-% Copyright (C) 2012, 2015, 2017, 2018 Peter Gerwinski
-%
-% This document is free software: you can redistribute it and/or
-% modify it either under the terms of the Creative Commons
-% Attribution-ShareAlike 3.0 License, or under the terms of the
-% GNU General Public License as published by the Free Software
-% Foundation, either version 3 of the License, or (at your option)
-% any later version.
-%
-% This document is distributed in the hope that it will be useful,
-% but WITHOUT ANY WARRANTY; without even the implied warranty of
-% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-% GNU General Public License for more details.
-%
-% You should have received a copy of the GNU General Public License
-% along with this document. If not, see <http://www.gnu.org/licenses/>.
-%
-% You should have received a copy of the Creative Commons
-% Attribution-ShareAlike 3.0 Unported License along with this
-% document. If not, see <http://creativecommons.org/licenses/>.
-
-\usepackage{amsfonts}
-\usepackage[colorlinks,allcolors=blue]{hyperref}
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-
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- \begin{quote}
- \addtolength{\leftskip}{0.6cm}%
-% \includegraphics[width=1cm]{Zeichen_101_-_Gefahrstelle,_StVO_1970.pdf}
- \makebox(0,0)[r]{\includegraphics[width=1cm]{Zeichen_101_-_Gefahrstelle,_StVO_1970.pdf}\hspace*{0.5em}}%
-% \hangindent 1.2cm
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-% Foobar Foobar Foobar Foobar Foobar Foobar Foobar Foobar
-% Foobar Foobar Foobar Foobar Foobar Foobar Foobar Foobar
-% Foobar Foobar Foobar Foobar Foobar Foobar Foobar Foobar
-% Foobar Foobar Foobar Foobar Foobar Foobar Foobar Foobar
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- \end{quote}
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diff --git a/20191212/pgscript.sty b/20191212/pgscript.sty
new file mode 120000
index 0000000000000000000000000000000000000000..95c888478c99ea7fda0fd11ccf669ae91be7178b
--- /dev/null
+++ b/20191212/pgscript.sty
@@ -0,0 +1 @@
+../common/pgscript.sty
\ No newline at end of file
diff --git a/20191212/pgslides.sty b/20191212/pgslides.sty
deleted file mode 100644
index 9a019ce99f03d27a17942facc56fe2145f46b6a6..0000000000000000000000000000000000000000
--- a/20191212/pgslides.sty
+++ /dev/null
@@ -1,233 +0,0 @@
-% pgslides.sty - LaTeX Settings for Lecture Slides
-% Copyright (C) 2012, 2013 Peter Gerwinski
-%
-% This document is free software: you can redistribute it and/or
-% modify it either under the terms of the Creative Commons
-% Attribution-ShareAlike 3.0 License, or under the terms of the
-% GNU General Public License as published by the Free Software
-% Foundation, either version 3 of the License, or (at your option)
-% any later version.
-%
-% This document is distributed in the hope that it will be useful,
-% but WITHOUT ANY WARRANTY; without even the implied warranty of
-% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
-% GNU General Public License for more details.
-%
-% You should have received a copy of the GNU General Public License
-% along with this document. If not, see <http://www.gnu.org/licenses/>.
-%
-% You should have received a copy of the Creative Commons
-% Attribution-ShareAlike 3.0 Unported License along with this
-% document. If not, see <http://creativecommons.org/licenses/>.
-
-\usepackage{amsfonts}
-\usepackage[british,german]{babel} % Yes, really "german" and not "ngerman".
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-\usepackage{pstricks}
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-
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-% local glyph = node.id ("glyph")
-% local function my_kerning (head)
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-% k.prev = t
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-% t.next = k
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-\lstdefinestyle{terminal}{basicstyle=\ttfamily\color{darkgreen},
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-\lstdefinestyle{cmd}{basicstyle=\ttfamily\color{red},
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diff --git a/20191212/pgslides.sty b/20191212/pgslides.sty
new file mode 120000
index 0000000000000000000000000000000000000000..5be1416f4216f076aa268901f52a15d775e43f64
--- /dev/null
+++ b/20191212/pgslides.sty
@@ -0,0 +1 @@
+../common/pgslides.sty
\ No newline at end of file
diff --git a/20191219/aufgabe-1.c b/20191219/aufgabe-1.c
new file mode 100644
index 0000000000000000000000000000000000000000..2afae773ac2d564771ab6dfb473eed664070d3e2
--- /dev/null
+++ b/20191219/aufgabe-1.c
@@ -0,0 +1,10 @@
+#include <stdio.h>
+#include <stdint.h>
+
+int main (void)
+{
+ uint64_t x = 4262939000843297096;
+ char *s = &x;
+ printf ("%s\n", s);
+ return 0;
+}
diff --git a/20191219/hp-uebung-20191219.pdf b/20191219/hp-uebung-20191219.pdf
new file mode 100644
index 0000000000000000000000000000000000000000..a48fb20d1f7ee23c36cca2df71e4366275067160
Binary files /dev/null and b/20191219/hp-uebung-20191219.pdf differ
diff --git a/20191219/hp-uebung-20191219.tex b/20191219/hp-uebung-20191219.tex
new file mode 100644
index 0000000000000000000000000000000000000000..f05c0fc5bea6dcc390d30db5c13660053e887075
--- /dev/null
+++ b/20191219/hp-uebung-20191219.tex
@@ -0,0 +1,202 @@
+% hp-uebung-20191219.pdf - Exercises on Low-Level Programming
+% Copyright (C) 2013, 2015, 2016, 2017, 2018, 2019 Peter Gerwinski
+%
+% This document is free software: you can redistribute it and/or
+% modify it either under the terms of the Creative Commons
+% Attribution-ShareAlike 3.0 License, or under the terms of the
+% GNU General Public License as published by the Free Software
+% Foundation, either version 3 of the License, or (at your option)
+% any later version.
+%
+% This document is distributed in the hope that it will be useful,
+% but WITHOUT ANY WARRANTY; without even the implied warranty of
+% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+% GNU General Public License for more details.
+%
+% You should have received a copy of the GNU General Public License
+% along with this document. If not, see <http://www.gnu.org/licenses/>.
+%
+% You should have received a copy of the Creative Commons
+% Attribution-ShareAlike 3.0 Unported License along with this
+% document. If not, see <http://creativecommons.org/licenses/>.
+
+% README: Trickprogrammierung, Thermometer-Baustein an I²C-Bus
+
+\documentclass[a4paper]{article}
+
+\usepackage{pgscript}
+\usepackage{gensymb}
+
+\newcommand{\ItwoC}{I\raisebox{0.5ex}{\footnotesize 2}C}
+\newcommand{\ITWOC}{I\raisebox{0.5ex}{\normalsize 2}C}
+
+\begin{document}
+
+ \thispagestyle{empty}
+
+ \section*{Hardwarenahe Programmierung\\
+ Übungsaufgaben -- 19.\ Dezember 2019}
+
+ Diese Übung enthält Punkteangaben wie in einer Klausur.
+ Um zu "`bestehen"', müssen Sie innerhalb von 60 Minuten
+ unter Verwendung ausschließlich zugelassener Hilfsmittel
+ 10 Punkte (von insgesamt \totalpoints) erreichen.
+
+ \exercise{Trickprogrammierung}
+
+ Wir betrachten das folgende Programm (Datei: \gitfile{hp}{20181210}{aufgabe-1.c}):
+ \begin{lstlisting}
+ #include <stdio.h>
+ #include <stdint.h>
+
+ int main (void)
+ {
+ uint64_t x = 4262939000843297096;
+ char *s = &x;
+ printf ("%s\n", s);
+ return 0;
+ }
+ \end{lstlisting}
+ Das Programm wird compiliert und auf einem 64-Bit-Little-Endian-Computer ausgeführt:
+ \begin{lstlisting}[style=terminal]
+ $ ¡gcc -Wall -O aufgabe-1.c -o aufgabe-1¿
+ aufgabe-1.c: In function `main':
+ aufgabe-1.c:7:13: warning: initialization from incompatible pointer type [...]
+ $ ¡./aufgabe-1¿
+ Hallo
+ \end{lstlisting}
+
+ \begin{itemize}
+ \item[(a)]
+ Erklären Sie die Warnung beim Compilieren. \points{2}
+ \item[(b)]
+ Erklären Sie die Ausgabe des Programms. \points{5}
+ \item[(c)]
+ Wie würde die Ausgabe des Programms auf einem 64-Bit-Big-Endian-Computer lauten? \points{3}
+ \end{itemize}
+ Hinweis: Modifizieren Sie das Programm
+ und lassen Sie sich Speicherinhalte ausgeben.
+
+ \exercise{Thermometer-Baustein an \ITWOC-Bus}
+
+ Eine Firma stellt einen elektronischen Thermometer-Baustein her,
+ den man über die serielle Schnittstelle (RS-232) an einen PC anschließen kann,
+ um die Temperatur auszulesen.
+ Nun wird eine Variante des Thermo"-meter-Bausteins entwickelt,
+ die die Temperatur zusätzlich über einen \ItwoC-Bus bereitstellt.
+
+ Um das neue Thermometer zu testen, wird es in ein Gefäß mit heißem Wasser gelegt,
+ das langsam auf Zimmertemperatur abkühlt.
+ Alle 10 Minuten liest ein Programm, das auf dem PC läuft,
+ die gemessene Temperatur über beide Schnittstellen aus
+ und erzeugt daraus die folgende Tabelle:
+
+ \begin{center}
+ \renewcommand{\arraystretch}{1.2}
+ \begin{tabular}{|c|c|c|}\hline
+ Zeit /\,min. & Temperatur per RS-232 /\,\degree C & Temperatur per \ItwoC\ /\,\degree C \\\hline\hline
+ \phantom{0}0 & 94 & 122 \\\hline
+ 10 & 47 & 244 \\\hline
+ 20 & 30 & 120 \\\hline
+ 30 & 24 & \phantom{0}24 \\\hline
+ 40 & 21 & 168 \\\hline
+ \end{tabular}
+ \end{center}
+
+ \begin{itemize}
+ \item[(a)]
+ Aus dem Vergleich der Meßdaten läßt sich
+ auf einen Fehler bei der \ItwoC-Übertragung schließen.\\
+ Um welchen Fehler handelt es sich,
+ und wie ergibt sich dies aus den Meßdaten?
+ \points{5}
+ \item[(b)]
+ Schreiben Sie eine C-Funktion \lstinline{uint8_t repair (uint8_t data)},
+ die eine über den \ItwoC-Bus empfangene fehlerhafte Temperatur \lstinline{data} korrigiert.
+ \points{5}
+ \end{itemize}
+
+\iffalse
+
+ \exercise{Lauflicht}
+
+ \begin{minipage}[t]{8cm}
+ An die vier Ports eines ATmega16-Mikrocontrollers sind Leuchtdioden angeschlossen:
+ \begin{itemize}
+ \item
+ von links nach rechts\\
+ an die Ports A, B, C und D,
+ \item
+ von oben nach unten\\
+ an die Bits Nr.\ 0 bis 7.
+
+ \bigskip
+
+ \includegraphics[width=3cm]{leds.jpg}
+ \end{itemize}
+ \end{minipage}\hfill
+ \begin{minipage}[t]{7cm}
+ Wir betrachten das folgende C-Programm (Datei: \gitfile{hp}{20181210}{aufgabe-2.c})
+ für diesen Mikrocontroller:
+
+ \begin{lstlisting}[gobble=6]
+ #include <avr/io.h>
+ #include <avr/interrupt.h>
+
+ int counter = 0;
+
+ ISR (TIMER0_COMP_vect)
+ {
+ PORTA = 1 << ((counter++ >> 6) & 7);
+ }
+
+ int main (void)
+ {
+ cli ();
+ TCCR0 = (1 << CS01) | (1 << CS00);
+ TIMSK = 1 << OCIE0;
+ sei ();
+ DDRA = 0xff;
+ while (1);
+ return 0;
+ }
+ \end{lstlisting}
+ \end{minipage}
+
+ \medskip
+
+ Das Programm bewirkt ein periodisches Lauflicht in der linken Spalte von oben nach unten.
+ Eine Animation davon finden Sie in der Datei \gitfile{hp}{20181210}{aufgabe-2.gif}.
+
+ \begin{itemize}
+ \item[(a)]
+ Wieso bewirkt das Programm überhaupt etwas, wenn doch das Hauptprogramm
+ nach dem Initialisieren lediglich eine Endlosschleife ausführt,
+ in der \emph{nichts\/} passiert? \points 3
+ \item[(b)]
+ Erklären Sie, wie die Anweisung
+ \begin{lstlisting}[gobble=8]
+ PORTA = 1 << ((counter++ >> 6) & 7);
+ \end{lstlisting}
+ \vspace{-\medskipamount}
+ das LED-Blinkmuster hervorruft. \points 6
+
+ Hinweis: Zerlegen Sie die eine lange Anweisung in mehrere kürzere.\\
+ Wenn nötig, verwenden Sie zusätzliche Variable für Zwischenergebnisse.
+ \item[(c)]
+ Was bedeutet "`\lstinline{ISR (TIMER0_COMP_vect)}"'? \points 1
+ \item[(d)]
+ Wieso leuchten die Leuchtdioden PB2 und PD1? \points 2
+ \end{itemize}
+
+\fi
+
+ \begin{flushright}
+ \textit{Viel Erfolg!}
+ \end{flushright}
+
+ \makeatletter
+ \immediate\write\@mainaux{\string\gdef\string\totalpoints{\arabic{points}}}
+ \makeatother
+
+\end{document}
diff --git a/20191219/pgslides.sty b/20191219/pgslides.sty
new file mode 120000
index 0000000000000000000000000000000000000000..5be1416f4216f076aa268901f52a15d775e43f64
--- /dev/null
+++ b/20191219/pgslides.sty
@@ -0,0 +1 @@
+../common/pgslides.sty
\ No newline at end of file
diff --git a/README.md b/README.md
index deaf53c5bb5d48ce184d60e08a1dd10fb66dde75..10ea859e0293f92c7bb0c52d394eb76da53530af 100644
--- a/README.md
+++ b/README.md
@@ -26,7 +26,8 @@ Vortragsfolien und Beispiele:
* [21.11.2019: Interrupts, volatile-Variable, Bibliotheken: Einführung](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191121/hp-20191121.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191121/)
* [28.11.2019: Präprozessor, Bibliotheken](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191128/hp-20191128.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191128/)
* [05.12.2019: Bibliotheken, Differentialgleichungen](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191205/hp-20191205.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191205/)
- * [12.12.2019: make, Byte-Reihenfolge - Endianness, Binärdarstellung negativer Zahlen, Speicherausrichtung - Alignment](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191212/hp-20191212.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191212/)
+ * [12.12.2019: make, Byte-Reihenfolge - Endianness](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191212/hp-20191212.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191212/)
+ * [19.12.2019: Binärdarstellung negativer Zahlen, Speicherausrichtung - Alignment](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191219/hp-20191219.pdf) [**(Beispiele)**](https://gitlab.cvh-server.de/pgerwinski/hp/tree/master/20191219/)
* [alle in 1 Datei](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/hp-slides-2019ws.pdf)
Übungsaufgaben:
@@ -41,6 +42,7 @@ Vortragsfolien und Beispiele:
* [28.11.2019: Datum-Bibliothek, Text-Grafik-Bibliothek, LED-Blinkmuster](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191128/hp-uebung-20191128.pdf)
* [05.12.2019: Löschen aus Strings, Hexdumps](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191205/hp-uebung-20191205.pdf)
* [12.12.2019: Kondensator, hüpfender Ball](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191212/hp-uebung-20191212.pdf)
+ * [19.12.2019: Trickprogrammierung, Thermometer-Baustein an I²C-Bus](https://gitlab.cvh-server.de/pgerwinski/hp/raw/master/20191219/hp-uebung-20191219.pdf)
Musterlösungen:
---------------