Define make targets

Makefile

 # TODO: Add default targets
+################################################################################
+#                        CO2 Ampel Firmware - Makefile                         #
+################################################################################
 
-all:
+## Run `make` to show available targets
+
+help:     ## Show this help.
+	@egrep -h '(\s##\s|^##\s)' $(MAKEFILE_LIST) | egrep -v '^--' | awk 'BEGIN {FS = ":.*?## "}; {printf "\033[32m  %-35s\033[0m %s\n", $$1, $$2}'
+
+build: ## Build. (board should be defined)
 ifdef board
 	pio -f -c vim run -e $(board)
 else
-	pio -f -c vim run
+	@echo "Please define board parameter:"
+	@echo "make build board=esp8266"
+	@echo "or"
+	@echo "make build board=esp32"
+	@exit 1
 endif
 
-upload:
+build_all: ## Build for all boards
+	pio -f -c vim run
+
+upload: ## Upload to ESP. (board should be defined)
+ifdef board
 	pio -f -c vim run --target upload -e $(board)
+else
+	@echo "Please define board parameter:"
+	@echo "make upload board=esp8266"
+	@exit 1
+endif
 
-clean:
+clean: ## Clean code
 	pio -f -c vim run --target clean
 
 program:
@@ -22,5 +43,5 @@ uploadfs:
 update:
 	pio -f -c vim update
 
-monitor:
+monitor: ## Monitor ESP output
 	pio device monitor --filter colorize