diff --git a/application.c b/application.c
index 0d8078f..87b1b16 100644
--- a/application.c
+++ b/application.c
@@ -77,6 +77,15 @@ static uint8_t channel_stop = CHANNEL_NUMBERS - 1; /**< last signal of range to
 /** timer ID for timer to measure activity timing */
 #define MONITOR_TIMER 2
 
+/** UART peripheral for signal reading (TX and RX are connected together)
+ *  @{
+ */
+#define UART_ID 2 /**< USART peripheral */
+#define UART_TX PA2 /**< pin used for USART TX */
+#define UART_RX PA3 /**< pin used for USART RX */
+#define UART_AF GPIO_AF7 /**< alternate function for UART pins */
+/** @} */
+
 size_t putc(char c)
 {
 	size_t length = 0; // number of characters printed
@@ -516,6 +525,109 @@ static void command_monitor(void* argument)
 	rcc_periph_clock_disable(RCC_TIM(MONITOR_TIMER)); // disable clock for timer peripheral
 }
 
+/** monitor single channel for activity
+ *  @param[in] argument channel number
+ */
+static void command_monitor_single(void* argument)
+{
+	(void)argument; // we won't use the argument
+
+	// get input channel
+	if (NULL == argument) {
+		puts("provide channel to monitor\n");
+		return;
+	}
+	const uint32_t channel = *(uint32_t*)argument; // get channel argument
+	if (!(channel < CHANNEL_NUMBERS)) { // verify argument
+		printf("channel %u out of range (0-%u)\n", channel, CHANNEL_NUMBERS - 1);
+		return;
+	}
+
+	// verify target voltage is OK
+	const float* voltages = measure_voltages(); // get target voltage
+	if (voltages[1] < 1.5) {
+		puts("target voltage too low: ");
+		print_fpu(voltages[1], 2);
+		puts(" < 1.5V\n");
+		return;
+	} else {
+		puts("target voltage: ");
+		print_fpu(voltages[1], 2);
+		puts("V\n");
+	}
+
+	// select channel
+	rcc_periph_clock_enable(GPIO_RCC(UART_RX)); // enable clock for USART RX pin port peripheral
+	gpio_mode_setup(GPIO_PORT(UART_RX), GPIO_MODE_INPUT, GPIO_PUPD_NONE, GPIO_PIN(UART_RX)); // use as input (it is pulled up by level shifter)
+	mux_select(channel); // select channel
+	gpio_clear(GPIO_PORT(SHIFT_EN_PIN), GPIO_PIN(SHIFT_EN_PIN)); // connect target voltage to level shifters pull-up
+
+	// show help
+	printf("CH%02u is pulled to target voltage by 10 kOhm\n", channel);
+	puts("high = 1.5-5.5V, 'X' shows multiple changes\n");
+	puts("press any key to stop monitoring\n");
+	puts("time (s) CH\n");
+
+	// setup timer to measure milliseconds
+	rcc_periph_clock_enable(RCC_TIM(MONITOR_TIMER)); // enable clock for timer peripheral
+	rcc_periph_reset_pulse(RST_TIM(MONITOR_TIMER)); // reset timer state
+	timer_disable_counter(TIM(MONITOR_TIMER)); // disable timer to configure it
+	timer_set_mode(TIM(MONITOR_TIMER), TIM_CR1_CKD_CK_INT, TIM_CR1_CMS_EDGE, TIM_CR1_DIR_UP); // set timer mode, use undivided timer clock, edge alignment (simple count), and count up
+	timer_set_prescaler(TIM(MONITOR_TIMER), (rcc_ahb_frequency / 2000) - 1); // generate half millisecond ticks (prescaler is not large enough for milliseconds)
+	timer_set_period(TIM(MONITOR_TIMER), 200 - 1); // set period to 0.1 seconds
+	timer_clear_flag(TIM(MONITOR_TIMER), TIM_SR_UIF); // clear update (overflow) flag
+	timer_update_on_overflow(TIM(MONITOR_TIMER)); // only use counter overflow as UEV source (use overflow as start time or timeout)
+	uint32_t seconds = 0; // count the 0.1 seconds using the overflow
+	timer_enable_counter(TIM(MONITOR_TIMER)); // enable timer
+
+	// start monitoring
+	bool channel_level = gpio_get(GPIO_PORT(UART_RX), GPIO_PIN(UART_RX)); // get initial level
+	uint8_t channel_changes = 1; // how many times the channel changed
+	while (!user_input_available) { // run until user breaks it
+		// time to do periodic checks
+		if (wakeup_flag || second_flag) {
+			iwdg_reset(); // kick the dog
+			wakeup_flag = false; // clear flag
+			second_flag = false; // clear flag
+		}
+		if (timer_get_flag(TIM(MONITOR_TIMER), TIM_SR_UIF)) { // 0.1 second has passed
+			timer_clear_flag(TIM(MONITOR_TIMER), TIM_SR_UIF); // clear flag
+			seconds++; // count the 0.1 seconds
+			if (channel_changes) { // there was some activity
+				// we print the change every 0.1 s instead of synchronously to rate limit the print (and overfill the buffer)
+				printf("%04u.%01u   ", seconds / 10, seconds % 10); // print current time stamp (change time stamp with 0.1s precision
+
+				if (channel_changes > 1) { // channel changed more than once
+					putc('X'); // show multiple changes
+				} else {
+					putc(' '); // show no or single change
+				}
+				if (channel_level) { // high level
+					putc('1');
+				} else {
+					putc('0');
+				}
+				puts("\n");
+				channel_changes = 0; // clear changes
+			}
+		}
+		// check is there is a change on a channel
+		const bool level_new = gpio_get(GPIO_PORT(UART_RX), GPIO_PIN(UART_RX)); // get new level
+		if (level_new != channel_level) { // channel changed
+			channel_changes = addu8_safe(channel_changes, 1);
+			channel_level = level_new; // save new level
+		}
+	}
+	user_input_get(); // clean input
+
+	// clean up
+	gpio_set(GPIO_PORT(SHIFT_EN_PIN), GPIO_PIN(SHIFT_EN_PIN)); // remove power from level shifters pull-up
+	mux_select(-1); // disable multiplexer
+	timer_disable_counter(TIM(MONITOR_TIMER)); // disable timer
+	rcc_periph_reset_pulse(RST_TIM(MONITOR_TIMER)); // reset timer state
+	rcc_periph_clock_disable(RCC_TIM(MONITOR_TIMER)); // disable clock for timer peripheral
+}
+
 /** set first channel of range to scan
  *  @param[in] argument optional pointer to first channel number
  */
@@ -702,6 +814,14 @@ static const struct menu_command_t menu_commands[] = {
 		.argument_description = "[0|3]",
 		.command_handler = &command_monitor,
 	},
+	{
+		.shortcut = 'M',
+		.name = "monitor_single",
+		.command_description = "monitor single channel activity",
+		.argument = MENU_ARGUMENT_UNSIGNED,
+		.argument_description = "channel",
+		.command_handler = &command_monitor_single,
+	},
 	{
 		.shortcut = 'c',
 		.name = "start",