diff --git a/main.c b/main.c
index d21018e..90c2dd4 100644
--- a/main.c
+++ b/main.c
@@ -39,9 +39,9 @@
 
 /* own libraries */
 #include "global.h" // board definitions
-#include "usart.h" // USART utilities
+//#include "usart.h" // USART utilities
 #include "usb_cdcacm.h" // USB CDC ACM utilities
-//#include "sensor_pzem.h" // PZEM electricity meter utilities
+#include "sensor_pzem.h" // PZEM electricity meter utilities
 #include "sensor_sdm120.h" // SDM120 electricity meter utilities
 #include "radio_esp8266.h" // ESP8266 WiFi SoC utilities
 
@@ -60,8 +60,8 @@ int _write(int file, char *ptr, int len)
 		for (i = 0; i < len; i++) {
 			if (ptr[i] == '\r' || ptr[i] == '\n') { // send CR+LF newline for most carriage return and line feed combination
 				if (newline==0 || (newline==ptr[i])) { // newline has already been detected
-					usart_putchar_nonblocking('\r'); // send newline over USART
-					usart_putchar_nonblocking('\n'); // send newline over USART
+					//usart_putchar_nonblocking('\r'); // send newline over USART
+					//usart_putchar_nonblocking('\n'); // send newline over USART
 					cdcacm_putchar('\r'); // send newline over USB
 					cdcacm_putchar('\n'); // send newline over USB
 					newline = ptr[i]; // remember the newline
@@ -70,7 +70,7 @@ int _write(int file, char *ptr, int len)
 					newline = 0; // clear new line
 				}
 			} else { // non-newline character
-				usart_putchar_nonblocking(ptr[i]); // send byte over USART
+				//usart_putchar_nonblocking(ptr[i]); // send byte over USART
 				cdcacm_putchar(ptr[i]); // send byte over USB
 				newline = 0; // clear new line
 			}
@@ -230,7 +230,7 @@ void main(void)
 	board_setup();
 	
 	// setup USART and USB for user communication
-    usart_setup(); // setup USART (for printing)
+    //usart_setup(); // setup USART (for printing)
 	cdcacm_setup(); // setup USB CDC ACM (for printing)
 	setbuf(stdout, NULL); // set standard out buffer to NULL to immediately print
 	setbuf(stderr, NULL); // set standard error buffer to NULL to immediately print
@@ -248,14 +248,11 @@ void main(void)
 	uint32_t ticks_time = rtc_get_counter_val(); // get time from internal RTC (since first start/power up)
 	printf("uptime: %02lu:%02lu:%02lu\n", ticks_time/(60*60), (ticks_time%(60*60))/60, (ticks_time%60)); // display time
 
-/*
 	// setup PZEM electricity meter
 	printf("setup PZEM-004 electricity meter: ");
 	sensor_pzem_setup(); // setup PZEM electricity meter
 	printf("OK\n");
-	//sensor_pzem_measurement_request(0xc0a80102, SENSOR_PZEM_ADDRESS);
 	sensor_pzem_measurement_request(0xc0a80101, SENSOR_PZEM_VOLTAGE);
-*/
 
 	// setup SDM120 electricity meter
 	printf("setup SDM120 electricity meter: ");
@@ -303,12 +300,14 @@ void main(void)
 	bool char_flag = false; // a new character has been received
 	while (true) { // infinite loop
 		iwdg_reset(); // kick the dog
+/*
 		while (usart_received) { // data received over UART
 			action = true; // action has been performed
 			led_toggle(); // toggle LED
 			c = usart_getchar(); // store receive character
 			char_flag = true; // notify character has been received
 		}
+*/
 		while (cdcacm_received) { // data received over USB
 			action = true; // action has been performed
 			led_toggle(); // toggle LED
@@ -332,7 +331,6 @@ void main(void)
 				}
 			}
 		}
-/*
 		while (sensor_pzem_measurement_received) { // measurement from electricity meter received
 			struct sensor_pzem_measurement_t measurement = sensor_pzem_measurement_decode(); // decode measurement
 			if (measurement.valid) { // only show valid measurement
@@ -360,7 +358,6 @@ void main(void)
 				}
 			}
 		}
-*/
 		while (sensor_sdm120_measurement_received) { // measurement from electricity meter received
 			float measurement = sensor_sdm120_measurement_decode(); // decode measurement
 			if (isnan(measurement)) {