diff --git a/tests/host/common/ArduinoMain.cpp b/tests/host/common/ArduinoMain.cpp
index 7fdf4b22f5..565c7942d0 100644
--- a/tests/host/common/ArduinoMain.cpp
+++ b/tests/host/common/ArduinoMain.cpp
@@ -129,24 +129,26 @@ void help (const char* argv0, int exitcode)
 		"	-b             - blocking tty/mocked-uart (default: not blocking tty)\n"
 		"	-S             - spiffs size in KBytes (default: %zd)\n"
 		"	-L             - littlefs size in KBytes (default: %zd)\n"
-		"	-v             - mock verbose\n"
-		"                  (negative value will force mismatched size)\n"
+		"\t                 (spiffs, littlefs: negative value will force mismatched size)\n"
+		"	-T             - show timestamp on output\n"
+		"	-v             - verbose\n"
 		, argv0, MOCK_PORT_SHIFTER, spiffs_kb, littlefs_kb);
 	exit(exitcode);
 }
 
 static struct option options[] =
 {
-	{ "help",		no_argument,		NULL, 'h' },
-	{ "fast",		no_argument,		NULL, 'f' },
-	{ "local",		no_argument,		NULL, 'l' },
-	{ "sigint",		no_argument,		NULL, 'c' },
-	{ "blockinguart",	no_argument,		NULL, 'b' },
-	{ "verbose",		no_argument,		NULL, 'v' },
-	{ "interface",		required_argument,	NULL, 'i' },
-	{ "spiffskb",		required_argument,	NULL, 'S' },
-	{ "littlefskb",		required_argument,	NULL, 'L' },
-	{ "portshifter",	required_argument,	NULL, 's' },
+	{ "help",           no_argument,        NULL, 'h' },
+	{ "fast",           no_argument,        NULL, 'f' },
+	{ "local",          no_argument,        NULL, 'l' },
+	{ "sigint",         no_argument,        NULL, 'c' },
+	{ "blockinguart",   no_argument,        NULL, 'b' },
+	{ "verbose",        no_argument,        NULL, 'v' },
+	{ "timestamp",      no_argument,        NULL, 'T' },
+	{ "interface",      required_argument,  NULL, 'i' },
+	{ "spiffskb",       required_argument,  NULL, 'S' },
+	{ "littlefskb",     required_argument,  NULL, 'L' },
+	{ "portshifter",    required_argument,  NULL, 's' },
 };
 
 void cleanup ()
@@ -182,7 +184,7 @@ int main (int argc, char* const argv [])
 
 	for (;;)
 	{
-		int n = getopt_long(argc, argv, "hlcfbvi:S:s:L:", options, NULL);
+		int n = getopt_long(argc, argv, "hlcfbvTi:S:s:L:", options, NULL);
 		if (n < 0)
 			break;
 		switch (n)
@@ -217,6 +219,9 @@ int main (int argc, char* const argv [])
 		case 'v':
 			mockdebug = true;
 			break;
+		case 'T':
+			serial_timestamp = true;
+			break;
 		default:
 			help(argv[0], EXIT_FAILURE);
 		}
diff --git a/tests/host/common/MockUART.cpp b/tests/host/common/MockUART.cpp
index 6c6a54ab35..67af7ed2cc 100644
--- a/tests/host/common/MockUART.cpp
+++ b/tests/host/common/MockUART.cpp
@@ -29,6 +29,8 @@
  */
 
 #include <unistd.h> // write
+#include <sys/time.h> // gettimeofday
+#include <time.h> // localtime
 
 #include "Arduino.h"
 #include "uart.h"
@@ -59,13 +61,35 @@ struct uart_
 	struct uart_rx_buffer_ * rx_buffer;
 };
 
+bool serial_timestamp = false;
+
 // write one byte to the emulated UART
 static void
 uart_do_write_char(const int uart_nr, char c)
 {
+	static bool w = false;
+
 	if (uart_nr >= UART0 && uart_nr <= UART1)
-		if (1 != write(uart_nr + 1, &c, 1))
-			fprintf(stderr, "Unable to write character to emulated UART stream: %d\n", c);
+	{
+		if (serial_timestamp && (c == '\n' || c == '\r'))
+		{
+			if (w)
+			{
+				FILE* out = uart_nr == UART0? stdout: stderr;
+				timeval tv;
+				gettimeofday(&tv, nullptr);
+				const tm* tm = localtime(&tv.tv_sec);
+				fprintf(out, "\r\n%d:%02d:%02d.%06d: ", tm->tm_hour, tm->tm_min, tm->tm_sec, (int)tv.tv_usec);
+				fflush(out);
+				w = false;
+			}
+		}
+		else
+		{
+			write(uart_nr + 1, &c, 1);
+			w = true;
+		}
+	}
 }
 
 // write a new byte into the RX FIFO buffer
diff --git a/tests/host/common/mock.h b/tests/host/common/mock.h
index e616167374..a908b2aba4 100644
--- a/tests/host/common/mock.h
+++ b/tests/host/common/mock.h
@@ -85,7 +85,7 @@ int ets_printf (const char* fmt, ...) __attribute__ ((format (printf, 1, 2)));
 int mockverbose (const char* fmt, ...) __attribute__ ((format (printf, 1, 2)));
 
 extern const char* host_interface; // cmdline parameter
-
+extern bool serial_timestamp;
 extern int mock_port_shifter;
 
 #define NO_GLOBAL_BINDING 0xffffffff