diff --git a/lambda/.gitignore b/lambda/.gitignore
index afd821e..0720336 100644
--- a/lambda/.gitignore
+++ b/lambda/.gitignore
@@ -2,3 +2,4 @@
 /Release/
 /lambda.elf
 /lambda.hex
+/lambda.lst
diff --git a/lambda/TODO b/lambda/TODO
index 8e0c2d8..1606b8c 100644
--- a/lambda/TODO
+++ b/lambda/TODO
@@ -3,5 +3,9 @@
 - Read up on "global" variables and modules
 
 * Functionality
-- Add beeper and beep when air gate valve should be closed and heating of
-  oxygen sensor should be switched off (or switch it off automatically?)
\ No newline at end of file
+- Add rules and alerts according to FIRE RULEZ!
+  
+* Circuit
+- Look at oxygen sensor voltage with voltmeter/oscilloscope - is the voltage
+  really so unstable?
+- Verify ADC voltages against voltmeter with other uC (ADC_OFFSET_MV)
\ No newline at end of file
diff --git a/lambda/adc.c b/lambda/adc.c
index 15b5f9d..f690ac2 100644
--- a/lambda/adc.c
+++ b/lambda/adc.c
@@ -14,8 +14,7 @@
 #include "adc.h"
 
 /**
- * Sets up a fake ISR to just return to where sleep_mode() was called
- * when ADC conversion is complete (ADC_vect).
+ * Returns to where sleep_mode() was called when ADC conversion is complete.
  */
 EMPTY_INTERRUPT(ADC_vect);
 
@@ -32,7 +31,6 @@
 }
 
 uint16_t getVoltage(uint8_t pin) {
-
 	ADMUX = (0b11110000 & ADMUX) | pin;
 
 	uint32_t overValue = 0;
diff --git a/lambda/alert.c b/lambda/alert.c
index 25b31f4..50ce6e8 100644
--- a/lambda/alert.c
+++ b/lambda/alert.c
@@ -52,6 +52,8 @@
 }
 
 void cancelAlert(void) {
+	beepCount = 0;
+	// turn beep off
 	TCCR1A &= ~(1 << COM1A0);
 	alertActive = false;
 }
diff --git a/lambda/command.c b/lambda/command.c
index f617d36..ff97dc1 100644
--- a/lambda/command.c
+++ b/lambda/command.c
@@ -6,6 +6,7 @@
  */
 
 #include <stdio.h>
+#include <stdlib.h>
 #include <stdbool.h>
 #include <string.h>
 #include <avr/interrupt.h>
@@ -15,6 +16,7 @@
 #include "command.h"
 
 bool simulation = false;
+bool logging = false;
 
 void command(char* data) {
 	char* fields[8];
@@ -24,20 +26,34 @@
 		fields[index++] = token;
 		token = strtok(NULL, " ");
 	}
-	if (strcmp(fields[0], "sien") == 0) {
+	if (strcmp(fields[0], "se") == 0) {
+		// simulation enable
 		simulation = true;
 		beep(1, 2);
 	}
-	else if (strcmp(fields[0], "sidi") == 0) {
+	else if (strcmp(fields[0], "sd") == 0) {
+		// simulation disable
 		simulation = false;
 		beep(1, 2);
 	}
-	else if (strcmp(fields[0], "menu") == 0) {
+	else if (strcmp(fields[0], "le") == 0) {
+		// logging enable
+		logging = true;
+		beep(1, 2);
+	}
+	else if (strcmp(fields[0], "ld") == 0) {
+		// logging disable
+		logging = false;
+		beep(1, 2);
+	}
+	else if (strcmp(fields[0], "cm") == 0) {
+		// cycle menu
 		cycleDisplay();
 		// updateMeas(meas);
 	}
-	else if (strcmp(fields[0], "tsal") == 0) {
-		alert(3, 20, "Beep Beep Beep!", fields[1]);
+	else if (strcmp(fields[0], "ta") == 0) {
+		// test alert
+		alert(1, 20, "Beep!", fields[1]);
 	}
 	else if (simulation) {
 		measurement meas = readMeas(fields);
@@ -48,3 +64,7 @@
 bool isSimulation(void) {
 	return simulation;
 }
+
+bool isLogging(void) {
+	return logging;
+}
diff --git a/lambda/command.h b/lambda/command.h
index 71e0546..7807be0 100644
--- a/lambda/command.h
+++ b/lambda/command.h
@@ -12,4 +12,6 @@
 
 bool isSimulation(void);
 
+bool isLogging(void);
+
 #endif /* COMMAND_H_ */
diff --git a/lambda/interrupts.c b/lambda/interrupts.c
index 76db62d..50f009a 100644
--- a/lambda/interrupts.c
+++ b/lambda/interrupts.c
@@ -19,7 +19,8 @@
 }
 
 void setupSleepMode(void) {
-	set_sleep_mode(SLEEP_MODE_ADC);
+	// SLEEP_MODE_ADC corrupts USART TX/RX data and causes a click in the beep
+	set_sleep_mode(SLEEP_MODE_IDLE);
 }
 
 void initInterrupts(void) {
@@ -43,6 +44,7 @@
 	// timer clock prescaler/64 = 15.625 kHz overflowing every 16 ms
 	TCCR0B |= (1 << CS01) | (1 << CS00);
 
+	// TODO use timer2 which continues running during SLEEP_MODE_ADC?
 	// toggle pin PB1 on compare match
 	// TCCR1A |= (1 << COM1A0);
 	// CTC mode, TOP OCR1A
@@ -51,6 +53,6 @@
 	TCCR1B |= (1 << CS11);
 	// toggles PB1 at 7.8 kHz generating a 3.9 kHz beep
 	// OCR1A = 16;
-	// less noisy
+	// less noisy 1.8 kHz
 	OCR1A = 32;
 }
diff --git a/lambda/lambda.c b/lambda/lambda.c
index 606df42..4c0ca1c 100644
--- a/lambda/lambda.c
+++ b/lambda/lambda.c
@@ -20,7 +20,6 @@
 #include <stdio.h>
 #include <stdbool.h>
 #include <string.h>
-#include <util/delay.h>
 #include <avr/io.h>
 #include <avr/interrupt.h>
 #include "USART.h"
@@ -57,8 +56,6 @@
 ISR(USART_RX_vect) {
 	if (bit_is_set(UCSR0A, RXC0) && ! usartReceived) {
 		char data = UDR0;
-		loop_until_bit_is_set(UCSR0A, UDRE0);
-		UDR0 = data;
 		if (dataCount < sizeof(usartData) - 1 && data != '\n' && data != '\r') {
 			usartData[dataCount++] = data;
 		} else {
@@ -84,15 +81,15 @@
 	alert(1, 2, "     Hello!     ", "");
 
 	measurement meas;
-	// memset(&meas, 0, sizeof(meas));
 
 	// main loop
 	while (1) {
 		if (intCount >= 62 && ! isSimulation()) {
 			intCount = 0;
-			// causes a click in the beep, because of sleep mode?
 			meas = measure();
-			printMeas(meas);
+			if (isLogging()) {
+				printMeas(meas);
+			}
 			updateMeas(meas);
 		}
 		if (buttonPressed) {
diff --git a/lambda/sensors.c b/lambda/sensors.c
index 74e1298..4c84c70 100644
--- a/lambda/sensors.c
+++ b/lambda/sensors.c
@@ -59,7 +59,7 @@
 };
 
 /**
- * Variables holding averaged voltages.
+ * Variables holding averaged voltages*8.
  */
 uint32_t lambdaVoltageAvg = 44 << 3; // Lambda 2.00
 uint32_t tempIVoltageAvg = 100 << 3; // 20°C
@@ -96,9 +96,9 @@
 
 measurement readMeas(char* fields[]) {
 	measurement meas;
-	meas.tempI  = strtol(fields[0], NULL, 10);
-	meas.tempO  = strtol(fields[1], NULL, 10);
-	meas.lambda = strtol(fields[2], NULL, 10);
+	meas.tempI  = atoi(fields[0]);
+	meas.tempO  = atoi(fields[1]);
+	meas.lambda = atoi(fields[2]);
 
 	return meas;
 }