Add UF2 build target

Author: tannewt

ports/esp32s2/Makefile

@@ -258,7 +258,7 @@ ESP_AUTOGEN_LD = $(BUILD)/esp-idf/esp-idf/esp32s2/esp32s2_out.ld $(BUILD)/esp-id
 
 FLASH_FLAGS = --flash_mode $(CIRCUITPY_ESP_FLASH_MODE) --flash_freq $(CIRCUITPY_ESP_FLASH_FREQ) --flash_size $(CIRCUITPY_ESP_FLASH_SIZE)
 
-all: $(BUILD)/firmware.bin
+all: $(BUILD)/firmware.bin $(BUILD)/firmware.uf2
 
 $(BUILD)/firmware.elf: $(OBJ) | $(ESP_IDF_COMPONENTS_EXPANDED) $(ESP_AUTOGEN_LD)
 	$(STEPECHO) "LINK $@"
@@ -274,6 +274,10 @@ $(BUILD)/circuitpython-firmware.bin: $(BUILD)/firmware.elf
 $(BUILD)/firmware.bin: $(BUILD)/esp-idf/partition_table/partition-table.bin $(BUILD)/esp-idf/bootloader/bootloader.bin $(BUILD)/circuitpython-firmware.bin
 	$(Q)$(PYTHON) ../../tools/join_bins.py $@ 0x1000 $(BUILD)/esp-idf/bootloader/bootloader.bin 0x8000 $(BUILD)/esp-idf/partition_table/partition-table.bin 0x10000 $(BUILD)/circuitpython-firmware.bin
 
+$(BUILD)/firmware.uf2: $(BUILD)/circuitpython-firmware.bin
+	$(STEPECHO) "Create $@"
+	$(Q)$(PYTHON3) $(TOP)/tools/uf2/utils/uf2conv.py -f 0xbfdd4eee -b 0x0000 -c -o $@ $^
+
 flash: $(BUILD)/firmware.bin
 	esptool.py --chip esp32s2 -p $(PORT) --no-stub -b 460800 --before=default_reset --after=hard_reset write_flash $(FLASH_FLAGS) 0x0000 $^