diff --git a/lambda-test/avrjunit.c b/lambda-test/avrjunit.c
index 1c48a5c..a7f5b22 100644
--- a/lambda-test/avrjunit.c
+++ b/lambda-test/avrjunit.c
@@ -1,6 +1,9 @@
 /*
  * avrjunit.c
  *
+ * Functions to run basic unit tests on an AVR micro controller and
+ * send a minimal JUnit test report XML via USART.
+ *
  *  Created on: 06.03.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda-test/avrjunit.h b/lambda-test/avrjunit.h
index dc77ac9..aaae229 100644
--- a/lambda-test/avrjunit.h
+++ b/lambda-test/avrjunit.h
@@ -1,6 +1,8 @@
 /*
  * avrjunit.h
  *
+ * Very basic unit test framework for AVR microcontroller code.
+ *
  *  Created on: 06.03.2015
  *      Author: dode@luniks.net
  *
@@ -25,6 +27,7 @@
  * the code accompanying the book Make: AVR Programming by Elliot Williams,
  * a great book and a pleasant read, that helped me tremendously to get
  * started with AVR programming.
+ *
  */
 
 /**
diff --git a/lambda-test/lambda-test.c b/lambda-test/lambda-test.c
index 9778ffd..32994b3 100644
--- a/lambda-test/lambda-test.c
+++ b/lambda-test/lambda-test.c
@@ -1,5 +1,7 @@
 /*
- * sensors-test.c
+ * lambda-test.c
+ *
+ * Unit tests for the lambda project.
  *
  *  Created on: 04.03.2015
  *      Author: dode@luniks.net
diff --git a/lambda/adc.c b/lambda/adc.c
index 9820c68..2153a46 100644
--- a/lambda/adc.c
+++ b/lambda/adc.c
@@ -1,6 +1,8 @@
 /*
  * adc.c
  *
+ * Functions to set up the ADC and get voltages from its ports.
+ *
  *  Created on: 11.03.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda/adc.h b/lambda/adc.h
index 0919830..cf04254 100644
--- a/lambda/adc.h
+++ b/lambda/adc.h
@@ -1,6 +1,8 @@
 /*
  * adc.h
  *
+ * Functions to set up the ADC and get voltages from its ports.
+ *
  *  Created on: 11.03.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda/integers.c b/lambda/integers.c
index c7c6b4f..6538787 100644
--- a/lambda/integers.c
+++ b/lambda/integers.c
@@ -1,6 +1,8 @@
 /*
  * integers.c
  *
+ * Functions to help with integers.
+ *
  *  Created on: 07.03.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda/integers.h b/lambda/integers.h
index b328c4e..e38e8ae 100644
--- a/lambda/integers.h
+++ b/lambda/integers.h
@@ -1,6 +1,8 @@
 /*
  * integers.h
  *
+ * Functions to help with integers.
+ *
  *  Created on: 07.03.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda/lambda.c b/lambda/lambda.c
index 99e36b2..6db5350 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -1,6 +1,9 @@
 /*
  * lambda.c
  *
+ * Program for an AVR micro controller based circuit to measure exhaust
+ * gas temperatures and residual oxygen of a wood oven.
+ *
  *  Created on: 22.02.2015
  *      Author: dode@luniks.net
  *
diff --git a/lambda/sensors.c b/lambda/sensors.c
index 0a23512..addd559 100644
--- a/lambda/sensors.c
+++ b/lambda/sensors.c
@@ -1,6 +1,8 @@
 /*
  * sensors.c
  *
+ * Functions to evaluate measurements from the sensors.
+ *
  *  Created on: 02.03.2015
  *      Author: dode@luniks.net
  *
@@ -108,7 +110,7 @@
 		int16_t lambdaVoltage, int16_t lambda) {
 	div_t lambdaT = div(lambda, 1000);
 
-	// TODO chars per line 16
+	// TODO LCD, 16 chars per line
 	char line0[40];
 	char line1[40];
 	snprintf(line0, sizeof(line0), "Ti %3d C %d   To %3d C %d\r\n", tempI, tempIVoltage, tempO, tempOVoltage);
diff --git a/lambda/sensors.h b/lambda/sensors.h
index 8ec8c9c..432e1ac 100644
--- a/lambda/sensors.h
+++ b/lambda/sensors.h
@@ -1,6 +1,8 @@
 /*
  * sensors.h
  *
+ * Functions to evaluate measurements from the sensors.
+ *
  *  Created on: 02.03.2015
  *      Author: dode@luniks.net
  *