diff --git a/Makefile-ARM b/Makefile-ARM
index efec78f..049d4de 100644
--- a/Makefile-ARM
+++ b/Makefile-ARM
@@ -67,31 +67,19 @@ TOOLCHAIN = arm-none-eabi-
 #                                                                            #
 ##############################################################################
 
-# avrdude, typical for AVR-based architectures.
+# Unlike with AVR, there is no one tool for uploading to all chips. Some
+# need 'lpc21isp', others (e.g. Arduinos) need 'bossac'.
 #
-# Flags:
-#   -c <programmer-type>      Typically stk500 or stk500v2.
-#   -b <baudrate>             Upload baud rate. Depends on the bootloader in
-#                             use. Not used for USB programmers.
-#   -p <mcu type>             See MCU above.
-#   -P <port>                 Serial port the electronics is connected to.
-#   -C <config file>          Optional, default is /etc/avrdude.conf.
+# To deal with this, we simply define the port here and do the rest directly
+# in the rules for the 'program' target.
 
-UPLOADER ?= avrdude
-# UPLOADER = <path-to-arduino-folder>/hardware/tools/avrdude
-
-ifndef UPLOADER_FLAGS
-UPLOADER_FLAGS  = -c stk500v2
-# UPLOADER_FLAGS += -b 19200
-# UPLOADER_FLAGS += -b 57600
-UPLOADER_FLAGS += -b 115200
-UPLOADER_FLAGS += -p $(MCU)
-# UPLOADER_FLAGS += -P COM1
-# UPLOADER_FLAGS += -P /dev/ttyACM0
-UPLOADER_FLAGS += -P /dev/ttyUSB0
-# UPLOADER_FLAGS += -C <path-to-arduino-folder>/hardware/tools/avrdude.conf
-endif
+# Frequency of the on-chip R/C oscillator or the on-board quartz crystal.
+F_CRYSTAL ?= 12000000
 
+# Serial port the electronics is connected to.
+UPLOADER_PORT ?= /dev/ttyUSB0
+#UPLOADER_PORT ?= /dev/ttyACM0
+#UPLOADER_PORT ?= com1
 
 ##############################################################################
 #                                                                            #
@@ -149,7 +137,13 @@ LIBS  = -lm
 all: $(PROGRAM).hex $(BUILDDIR)/$(PROGRAM).lst $(BUILDDIR)/$(PROGRAM).sym size
 
 program: $(PROGRAM).hex config.h
-	$(UPLOADER) $(UPLOADER_FLAGS) -U flash:w:$(PROGRAM).hex
+	@echo
+	@echo "To let the bootloader complete his work, connect now PIO0_1 to GND,"
+	@echo "then press Reset for a moment. The bootloader should begin uploading."
+	@echo "After being done, disconnect PIO0_1 and press reset again. On a"
+	@echo "Gen7-ARM, PIO0_1 is the Step pin of the Z stepper driver."
+	@echo
+	lpc21isp -control $< $(UPLOADER_PORT) 115200 $(F_CRYSTAL)
 
 $(BUILDDIR)/teacup.elf: $(BUILDDIR)/startup.o