add makefile, improve gitignore, formatting

.gitignore

@@ -1,2 +1,3 @@
 /cmake-build-debug/
-.idea
+/build/
+/.idea

Makefile

@@ -0,0 +1,25 @@
+BUILD_DIR := build
+EXECUTABLE := modbus
+
+.PHONY: all build run clean rebuild debug release help
+all: build
+
+# Configure and build the project
+build:
+	@mkdir -p $(BUILD_DIR)
+	@cd $(BUILD_DIR) && cmake ..
+	@cmake --build $(BUILD_DIR)
+	@echo "Build complete. Executable: $(BUILD_DIR)/$(EXECUTABLE)"
+
+# Run the built executable, build if needed
+run: build
+	@echo "Running $(EXECUTABLE)..."
+	@./$(BUILD_DIR)/$(EXECUTABLE)
+
+# Clean build artifacts
+clean:
+	@rm -rf $(BUILD_DIR)
+	@echo "Build directory cleaned"
+
+# Rebuild from scratch
+rebuild: clean build

src/main_simpletest.c

@@ -1,3 +1,5 @@
+// This test shows how the library could be used to implement a Modbus RTU device
+
 #include <stdio.h>
 #include "modbus.h"
 #include "hexdump.h"