Show COVID-19 exposure notification statistics

Based on !390 (merged)

Displays how many unique MACs (aka phones) which send exposure notifications have been seen during the last 100 seconds.

It tries to distinguish between Apple and Google devices based on a heuristic mentioned in https://github.com/znuh/microbit-corona-scanner. The user can choose if they want the LEDs and/or the vibration motor to show newly discovered MACs / exposure notifications.

Loosely based on:

• https://github.com/kauzu/CoronaAppDetector
• https://github.com/frankrieger/CoronaAppDetectorM5StickC
• https://github.com/znuh/microbit-corona-scanner

Most of the logic resides in a plain Python script and can be modified by the user as needed.

epicardium/modules/leds.c

 #include "leds.h"
 #include "pmic.h"
 #include "FreeRTOS.h"
+#include "timers.h"
 #include "task.h"
 #include "epicardium.h"
 #include "modules.h"
@@ -128,6 +129,33 @@ int epic_leds_get_rocket(int led)
 	return ret;
 }
 
+static StaticTimer_t flash_timer_data[3];
+static TimerHandle_t flash_timer[] = { NULL, NULL, NULL };
+
+static void rocket_timer_callback(TimerHandle_t flash_timer)
+{
+	uint32_t id = (uint32_t)pvTimerGetTimerID(flash_timer);
+	epic_leds_set_rocket(id, 0);
+}
+
+void epic_leds_flash_rocket(int led, uint8_t value, int millis)
+{
+	int ticks  = millis * (configTICK_RATE_HZ / 1000);
+	int32_t id = led;
+	if (flash_timer[id] == NULL) {
+		flash_timer[id] = xTimerCreateStatic(
+			"flashtimer",
+			ticks,
+			pdFALSE,
+			(void *)id,
+			rocket_timer_callback,
+			&flash_timer_data[id]
+		);
+		epic_leds_set_rocket(led, value);
+	}
+	epic_leds_set_rocket(led, value);
+	xTimerChangePeriod(flash_timer[id], ticks, 0);
+}
 void epic_set_flashlight(bool power)
 {
 	hwlock_acquire(HWLOCK_I2C);