Add Makefile, currently configured for ATTiny45

Makefile

@@ -0,0 +1,48 @@
+# This Makefile can be used to build and upload PSNee on an ATTiny45. It can easily be adapted for
+# other AVRs.
+# "make upload" will build and upload for ATTiny45
+# "make upload ATTINY_NUMBER=85" will build and upload for ATTiny85, etc.
+
+# Change this number to 85 or 25 as needed for ATTiny25 and ATTiny85
+ATTINY_NUMBER ?= 45
+# Use arduino-cli board details -b $(BOARD) to see other flags.
+BOARD = ATTinyCore:avr:attinyx5:chip=$(ATTINY_NUMBER),clock=8internal
+CPP_EXTRA_FLAGS = -DATTINY_X5
+OUTPUT_DIR = build-t$(ATTINY_NUMBER)
+
+# Use "arduino-cli board list" to find this
+SERIAL = /dev/ttyACM0
+
+ATTINYCOREURL = http://drazzy.com/package_drazzy.com_index.json
+
+
+# This is believed to match how arduino-cli works, i.e. it uses the name of the
+# current directory to infer the name of the main .ino file.
+PROJECT_FILE = $(notdir $(CURDIR)).ino
+
+# Use 'make DEBUG=1 upload' to build and upload the debug version
+DEBUG ?= 0
+ifeq ($(DEBUG), 1)
+  CPP_EXTRA_FLAGS += -DPSNEEDEBUG
+  OUTPUT_DIR = debug-build
+endif
+
+all: compile
+
+clean:
+	rm -rf $(OUTPUT_DIR)
+
+compile: $(OUTPUT_DIR)/$(PROJECT_FILE).hex
+
+$(OUTPUT_DIR)/$(PROJECT_FILE).hex: $(wildcard *.cpp) $(wildcard *.h) $(PROJECT_FILE)
+	arduino-cli compile --build-property compiler.cpp.extra_flags="$(CPP_EXTRA_FLAGS)" --output-dir "$(OUTPUT_DIR)" -b "$(BOARD)" -e
+
+# This worked uploading via ISCP with a Pololu programmer.
+# We also set fuses, in particular to unset CKDIV8 to have the full clock speed.
+upload: compile
+	arduino-cli upload -v --input-dir "$(OUTPUT_DIR)" -P stk500 -b  "$(BOARD)" -p $(SERIAL) -t
+	avrdude -c stk500v2 -p t$(ATTINY_NUMBER) -P $(SERIAL) -U lfuse:w:0xE2:m -U hfuse:w:0xDF:m
+
+install-core:
+	arduino-cli core update-index --additional-urls "$(ATTINYCOREURL)"
+	arduino-cli core install ATTinyCore:avr --additional-urls "$(ATTINYCOREURL)"