diff --git a/solutions/04_system/silly/Makefile b/solutions/04_system/silly/Makefile
index c37afab..b7be12c 100644
--- a/solutions/04_system/silly/Makefile
+++ b/solutions/04_system/silly/Makefile
@@ -1,19 +1,5 @@
-# Makefile for CMake project with intelligent configuration
+EXE=app
+SRCS=$(wildcard *.c)
 
-# Default target
-all: build/build.ninja 
-	cmake --build build
-
-# Create build directory and generate build files if needed
-build/build.ninja : CMakeLists.txt
-	cmake -S . -B build -G "Ninja"
-
-# Clean build directory
-clean:
-	rm -rf build
-
-# Rebuild from scratch
-rebuild: clean all
-
-# Phony targets (targets that don't represent files)
-.PHONY: all clean rebuild
\ No newline at end of file
+# Include the standard application Makefile for the CSEL1 labs
+include ./appl.mk
diff --git a/src/03-led-controller/CMakeLists.txt b/src/03-led-controller/CMakeLists.txt
index 9faf9c8..62abb23 100644
--- a/src/03-led-controller/CMakeLists.txt
+++ b/src/03-led-controller/CMakeLists.txt
@@ -2,4 +2,4 @@ cmake_minimum_required(VERSION 3.28)
 project(led-controller)
 
 include(../nanopi.cmake)
-add_executable(main main.c)
+add_executable(led-controller main.c)
diff --git a/src/03-led-controller/justfile b/src/03-led-controller/justfile
new file mode 100644
index 0000000..b965e1c
--- /dev/null
+++ b/src/03-led-controller/justfile
@@ -0,0 +1,5 @@
+build:
+    cmake -S . -B build && cmake --build build
+
+clean:
+    rm -rf build
diff --git a/src/03-led-controller/main.c b/src/03-led-controller/main.c
index c7b5246..c2bf45e 100644
--- a/src/03-led-controller/main.c
+++ b/src/03-led-controller/main.c
@@ -1,7 +1,102 @@
-#include <stdio.h>
+/**
+ * Copyright 2018 University of Applied Sciences Western Switzerland / Fribourg
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Project: HEIA-FR / HES-SO MSE - MA-CSEL1 Laboratory
+ *
+ * Abstract: System programming -  file system
+ *
+ * Purpose: NanoPi silly status led control system
+ *
+ * Autĥor:  Daniel Gachet
+ * Date:    07.11.2018
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <time.h>
+#include <unistd.h>
 
-int main() {
-    printf("Led controller");
+/*
+ * status led - gpioa.10 --> gpio10
+ * power led  - gpiol.10 --> gpio362
+ */
+#define GPIO_EXPORT   "/sys/class/gpio/export"
+#define GPIO_UNEXPORT "/sys/class/gpio/unexport"
+#define GPIO_LED      "/sys/class/gpio/gpio10"
+#define LED           "10"
+
+static int open_led()
+{
+    // unexport pin out of sysfs (reinitialization)
+    int f = open(GPIO_UNEXPORT, O_WRONLY);
+    write(f, LED, strlen(LED));
+    close(f);
+
+    // export pin to sysfs
+    f = open(GPIO_EXPORT, O_WRONLY);
+    write(f, LED, strlen(LED));
+    close(f);
+
+    // config pin
+    f = open(GPIO_LED "/direction", O_WRONLY);
+    write(f, "out", 3);
+    close(f);
+
+    // open gpio value attribute
+    f = open(GPIO_LED "/value", O_RDWR);
+    return f;
+}
+
+int main(int argc, char* argv[])
+{
+    long duty   = 2;     // %
+    long period = 1000;  // ms
+    if (argc >= 2) period = atoi(argv[1]);
+    period *= 1000000;  // in ns
+
+    // compute duty period...
+    long p1 = period / 100 * duty;
+    long p2 = period - p1;
+
+    int led = open_led();
+    pwrite(led, "1", sizeof("1"), 0);
+
+    struct timespec t1;
+    clock_gettime(CLOCK_MONOTONIC, &t1);
+
+    int k = 0;
+    while (1) {
+        struct timespec t2;
+        clock_gettime(CLOCK_MONOTONIC, &t2);
+
+        long delta =
+            (t2.tv_sec - t1.tv_sec) * 1000000000 + (t2.tv_nsec - t1.tv_nsec);
+
+        int toggle = ((k == 0) && (delta >= p1)) | ((k == 1) && (delta >= p2));
+        if (toggle) {
+            t1 = t2;
+            k  = (k + 1) % 2;
+            if (k == 0)
+                pwrite(led, "1", sizeof("1"), 0);
+            else
+                pwrite(led, "0", sizeof("0"), 0);
+        }
+    }
 
     return 0;
-}
+}
\ No newline at end of file
diff --git a/src/appl.mk b/src/appl.mk
new file mode 100644
index 0000000..667cb94
--- /dev/null
+++ b/src/appl.mk
@@ -0,0 +1,45 @@
+CFLAGS=-Wall -Wextra -g -c -O0 -MD -std=gnu11
+CFLAGS+=$(EXTRA_CFLAGS)
+
+TOOLCHAIN_PATH=/buildroot/output/host/usr/bin/
+TOOLCHAIN=$(TOOLCHAIN_PATH)aarch64-linux-
+CFLAGS+=-mcpu=cortex-a53 -funwind-tables
+##CFLAGS+=-O2 -fno-omit-frame-pointer
+OBJDIR=.obj/nano
+EXEC=$(EXE)
+
+ifeq ($(target),host)
+EXEC=$(EXE)_h
+endif
+
+CC=$(TOOLCHAIN)gcc
+LD=$(TOOLCHAIN)gcc
+AR=$(TOOLCHAIN)ar
+STRIP=$(TOOLCHAIN)strip
+
+OBJDIR=.obj/$(target)
+OBJS= $(addprefix $(OBJDIR)/, $(SRCS:.c=.o))
+
+$(OBJDIR)/%o: %c
+	$(CC) $(CFLAGS) $< -o $@
+
+all: $(OBJDIR)/ $(EXEC)
+
+$(EXEC): $(OBJS) $(LINKER_SCRIPT)
+	$(LD) $(OBJS) $(LDFLAGS) -o $@
+
+$(OBJDIR)/:
+	mkdir -p $(OBJDIR)
+
+clean:
+	rm -Rf $(OBJDIR) $(EXEC) $(EXEC)_s *~
+
+clean_all: clean
+	rm -Rf .obj $(EXE) $(EXE)_s $(EXE)_a $(EXE)_a_s $(EXE)_h $(EXE)_h_s
+
+-include $(OBJS:.o=.d)
+
+.PHONY: all clean clean_all
+
+
+