examples/rust-matter-light: Make periph_rtc feature optional. If not …

…supported, get seconds since UNIX epoch from ztimer_sec

examples/rust-matter-light/Makefile

@@ -29,7 +29,9 @@ APPLICATION_RUST_MODULE = rust_matter_light
 BASELIBS += $(APPLICATION_RUST_MODULE).module
 
 FEATURES_REQUIRED += rust_target
-FEATURES_REQUIRED += periph_rtc
+
+# Use RTC for sys_epoch, otherwise ztimer
+FEATURES_OPTIONAL += periph_rtc
 
 # Comment this line in to activate storing & loading runtime configurations
 # NOTE: To use this feature, a PersistenceManager (in 'src/persist.rs') must be implemented for the target platform
@@ -43,6 +45,7 @@ USEMODULE += shell_cmd_heap
 USEMODULE += ztimer
 USEMODULE += ztimer_msec
 USEMODULE += ztimer_usec
+USEMODULE += ztimer_sec
 USEMODULE += ps
 USEMODULE += random
 USEMODULE += periph_hwrng

examples/rust-matter-light/utils.c

@@ -1,13 +1,24 @@
+#include <stdint.h>
+#include "modules.h"
+
+#if IS_USED(MODULE_PERIPH_RTC)
 #include "periph/rtc.h"
-#include <time.h>
+#else
+#include "ztimer.h"
+#endif
 
 // RIOT_EPOCH(2020) in seconds since UNIX Epoch
 #define RIOT_EPOCH_SECS 1577833200;
 
 uint32_t get_seconds_since_unix_epoch(void) {
-    // Get time since RIOT_EPOCH from RTC
+#if IS_USED(MODULE_PERIPH_RTC)
+    // Get seconds since RIOT_EPOCH from RTC
     struct tm now;
     rtc_get_time(&now);
-    // Add to RIOT_EPOCH to get current seconds since UNIX epoch
-    return rtc_mktime(&now) + RIOT_EPOCH_SECS;
+    // Add to RIOT_EPOCH to get seconds since UNIX epoch
+    return RIOT_EPOCH_SECS + rtc_mktime(&now);
+#else
+    // Get elapsed seconds from ztimer
+    return RIOT_EPOCH_SECS + ztimer_now(ZTIMER_SEC);
+#endif
 }