apple2: Generate a special bootloader for AT2 (QFN32) boards

This is required because pin PA10 (rotary select) is reassigned
for an Apple2 stepper phase. The regular bootloader is unaware of
this and will spuriously enter update mode if the phase signal is
low when the Gotek powers on or resets.

Thanks to Mauricio Matte for testing.

Author: keirf

Makefile

@@ -34,9 +34,12 @@ logfile-%: FORCE
 	$(MAKE) target mcu=$* target=apple2 level=logfile
 	$(MAKE) target mcu=$* target=quickdisk level=logfile
 
+apple2-bootloader-%: FORCE
+	$(MAKE) target mcu=$* target=apple2-bootloader level=prod
+
 all-%: FORCE prod-% debug-% logfile-% ;
 
-all: FORCE all-stm32f105 all-at32f435 ;
+all: FORCE all-stm32f105 all-at32f435 apple2-bootloader-stm32f105;
 
 clean: FORCE
 	rm -rf out
@@ -112,6 +115,14 @@ _dist: FORCE
 	  out/$(mcu)/logfile/quickdisk/target.bin $(mcu) & \
 	wait
 
+_dist_apple2_at2_bootloader: f := $(t)/alt/apple2/at2-bootloader
+_dist_apple2_at2_bootloader: n := $(PROJ)-apple2-at2-bootloader-$(VER)
+_dist_apple2_at2_bootloader: FORCE
+	mkdir -p $(f)
+	cd out/stm32f105/prod/apple2-bootloader; \
+	  cp -a target.dfu $(f)/$(n).dfu; \
+	  cp -a target.hex $(f)/$(n).hex
+
 dist: level := prod
 dist: t := $(ROOT)/out/$(PROJ)-$(VER)
 dist: FORCE all
@@ -126,6 +137,7 @@ dist: FORCE all
 	$(MAKE) _legacy_dist mcu=stm32f105 level=$(level) t=$(t)
 	$(MAKE) _dist mcu=stm32f105 n=at415-st105 level=$(level) t=$(t)
 	$(MAKE) _dist mcu=at32f435 n=at435 level=$(level) t=$(t)
+	$(MAKE) _dist_apple2_at2_bootloader level=$(level) t=$(t)
 	$(PYTHON) scripts/mk_qd.py --window=6.5 $(t)/alt/quickdisk/Blank.qd
 	cp -a COPYING $(t)/
 	cp -a README $(t)/

Rules.mk

@@ -19,7 +19,16 @@ FLAGS += -Wundef
 
 ## STM32F105
 ifeq ($(mcu),stm32f105)
+
 FLAGS += -mcpu=cortex-m3
+
+# Build hack for an Apple2-specific bootloader which knows that QFN32 pin
+# PA10 is reassigned.
+ifeq ($(target),apple2-bootloader)
+override target=bootloader
+FLAGS += -DAPPLE2_BOOTLOADER=1
+endif
+
 ifeq ($(target),bootloader)
 # Debug bootloader doesn't fit in 32kB
 override level=prod

src/gotek/board.c

@@ -84,7 +84,7 @@ unsigned int board_get_buttons(void)
         x &= _rbit32(gpioc->idr) >> 23;
     x = ~x & 7;
 
-#if TARGET == TARGET_apple2
+#if (TARGET == TARGET_apple2) || defined(APPLE2_BOOTLOADER)
     /* Apple 2: QFN32 select pin PA10 is reassigned as stepper phase #0. */
     if (mcu_package == MCU_QFN32)
         return x;