Add initial RP2040 support

The RP2040 is new microcontroller from Raspberry Pi that features
two Cortex M0s and eight PIO state machines that are good for
crunching lots of data. It has 264k RAM and a built in UF2
bootloader too.

Datasheet: https://pico.raspberrypi.org/files/rp2040_datasheet.pdf

Author: tannewt

.github/workflows/build.yml

@@ -177,6 +177,7 @@ jobs:
         - "8086_commander"
         - "ADM_B_NRF52840_1"
         - "TG-Watch"
+        - "adafruit_feather_rp2040"
         - "aloriumtech_evo_m51"
         - "aramcon_badge_2019"
         - "arduino_mkr1300"
@@ -294,6 +295,7 @@ jobs:
         - "pyruler"
         - "qtpy_m0"
         - "qtpy_m0_haxpress"
+        - "raspberry_pi_pico"
         - "raytac_mdbt50q-db-40"
         - "robohatmm1_m4"
         - "sam32"

.gitmodules

@@ -75,7 +75,7 @@
 	url = https://github.com/adafruit/nrfx.git
 [submodule "lib/tinyusb"]
 	path = lib/tinyusb
-	url = https://github.com/hathach/tinyusb.git
+	url = https://github.com/tannewt/tinyusb.git
 	branch = master
 	fetchRecurseSubmodules = false
 [submodule "tools/huffman"]
@@ -171,3 +171,6 @@
 [submodule "frozen/Adafruit_CircuitPython_LC709203F"]
 	path = frozen/Adafruit_CircuitPython_LC709203F
 	url = https://github.com/adafruit/Adafruit_CircuitPython_LC709203F
+[submodule "ports/raspberrypi/sdk"]
+	path = ports/raspberrypi/sdk
+	url = https://github.com/raspberrypi/pico-sdk.git

Makefile

@@ -255,6 +255,7 @@ stubs:
 	@$(PYTHON) tools/extract_pyi.py shared-bindings/ $(STUBDIR)
 	@$(PYTHON) tools/extract_pyi.py extmod/ulab/code/ $(STUBDIR)/ulab
 	@$(PYTHON) tools/extract_pyi.py ports/atmel-samd/bindings $(STUBDIR)
+	@$(PYTHON) tools/extract_pyi.py ports/raspberrypi/bindings $(STUBDIR)
 	@$(PYTHON) setup.py -q sdist
 
 .PHONY: check-stubs

conf.py

@@ -189,6 +189,7 @@
                     "ports/nrf/nrfx",
                     "ports/nrf/peripherals",
                     "ports/nrf/usb",
+                    "ports/raspberrypi/sdk",
                     "ports/stm/st_driver",
                     "ports/stm/packages",
                     "ports/stm/peripherals",

docs/supported_ports.rst

@@ -13,8 +13,9 @@ is limited.
 
     ../ports/atmel-samd/README
     ../ports/cxd56/README
+    ../ports/esp32s2/README
     ../ports/litex/README
     ../ports/mimxrt10xx/README
     ../ports/nrf/README
+    ../ports/raspberrypi/README
     ../ports/stm/README
-    ../ports/esp32s2/README

lib/tinyusb

@@ -0,0 +1 @@
+build-*/

ports/raspberrypi/.gitignore

@@ -0,0 +1,273 @@
+# This file is part of the MicroPython project, http://micropython.org/
+#
+# The MIT License (MIT)
+#
+# SPDX-FileCopyrightText: Copyright (c) 2019 Dan Halbert for Adafruit Industries
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+
+# Select the board to build for.
+ifeq ($(BOARD),)
+  $(error You must provide a BOARD parameter)
+else
+  ifeq ($(wildcard boards/$(BOARD)/.),)
+    $(error Invalid BOARD specified)
+  endif
+endif
+
+# If the build directory is not given, make it reflect the board name.
+BUILD ?= build-$(BOARD)
+
+include ../../py/mkenv.mk
+# Board-specific
+include boards/$(BOARD)/mpconfigboard.mk
+# Port-specific
+include mpconfigport.mk
+# CircuitPython-specific
+include $(TOP)/py/circuitpy_mpconfig.mk
+
+# qstr definitions (must come before including py.mk)
+QSTR_DEFS = qstrdefsport.h
+
+# include py core make definitions
+include $(TOP)/py/py.mk
+
+include $(TOP)/supervisor/supervisor.mk
+
+# Include make rules and variables common across CircuitPython builds.
+include $(TOP)/py/circuitpy_defns.mk
+
+CROSS_COMPILE = arm-none-eabi-
+
+HAL_DIR=hal/$(MCU_SERIES)
+
+INC += -I. \
+       -I../.. \
+       -I../lib/mp-readline \
+       -I../lib/timeutils \
+       -Iboards/$(BOARD) \
+       -Iboards/ \
+       -isystem sdk/ \
+       -isystem sdk/src/common/pico_base/include/ \
+       -isystem sdk/src/common/pico_binary_info/include/ \
+       -isystem sdk/src/common/pico_stdlib/include/ \
+       -isystem sdk/src/common/pico_sync/include/ \
+       -isystem sdk/src/common/pico_time/include/ \
+       -isystem sdk/src/common/pico_util/include/ \
+       -isystem sdk/src/rp2040/hardware_regs/include/ \
+       -isystem sdk/src/rp2040/hardware_structs/include/ \
+       -isystem sdk/src/rp2_common/hardware_adc/include/ \
+       -isystem sdk/src/rp2_common/hardware_base/include/ \
+       -isystem sdk/src/rp2_common/hardware_claim/include/ \
+       -isystem sdk/src/rp2_common/hardware_clocks/include/ \
+       -isystem sdk/src/rp2_common/hardware_dma/include/ \
+       -isystem sdk/src/rp2_common/hardware_flash/include/ \
+       -isystem sdk/src/rp2_common/hardware_gpio/include/ \
+       -isystem sdk/src/rp2_common/hardware_irq/include/ \
+       -isystem sdk/src/rp2_common/hardware_i2c/include/ \
+       -isystem sdk/src/rp2_common/hardware_pio/include/ \
+       -isystem sdk/src/rp2_common/hardware_pll/include/ \
+       -isystem sdk/src/rp2_common/hardware_resets/include/ \
+       -isystem sdk/src/rp2_common/hardware_spi/include/ \
+       -isystem sdk/src/rp2_common/hardware_sync/include/ \
+       -isystem sdk/src/rp2_common/hardware_timer/include/ \
+       -isystem sdk/src/rp2_common/hardware_uart/include/ \
+       -isystem sdk/src/rp2_common/hardware_watchdog/include/ \
+       -isystem sdk/src/rp2_common/hardware_xosc/include/ \
+       -isystem sdk/src/rp2_common/pico_multicore/include/ \
+       -isystem sdk/src/rp2_common/pico_fix/rp2040_usb_device_enumeration/include/ \
+       -isystem sdk/src/rp2_common/pico_stdio/include/ \
+       -isystem sdk/src/rp2_common/pico_printf/include/ \
+       -isystem sdk/src/rp2_common/pico_float/include/ \
+       -isystem sdk/src/rp2_common/pico_platform/include/ \
+       -isystem sdk/src/rp2_common/pico_runtime/printf/include/ \
+       -isystem sdk/src/rp2_common/pico_bootrom/include/ \
+       -Isdk_config \
+       -I../../lib/tinyusb/src \
+       -I../../supervisor/shared/usb \
+       -I$(BUILD)
+
+# Pico specific configuration
+CFLAGS += -DPICO_ON_DEVICE=1 -DPICO_NO_BINARY_INFO=0 -DPICO_TIME_DEFAULT_ALARM_POOL_DISABLED=1 -DPICO_DIVIDER_CALL_IDIV0=0 -DPICO_DIVIDER_CALL_LDIV0=0 -DPICO_DIVIDER_HARDWARE=1 -DPICO_DOUBLE_ROM=1 -DPICO_FLOAT_ROM=1 -DPICO_MULTICORE=1 -DPICO_BITS_IN_RAM=0 -DPICO_DIVIDER_IN_RAM=0 -DPICO_DOUBLE_PROPAGATE_NANS=0 -DPICO_DOUBLE_IN_RAM=0 -DPICO_MEM_IN_RAM=0 -DPICO_FLOAT_IN_RAM=0 -DPICO_FLOAT_PROPAGATE_NANS=1 -DPICO_NO_FLASH=0 -DPICO_COPY_TO_RAM=0 -DPICO_DISABLE_SHARED_IRQ_HANDLERS=0
+OPTIMIZATION_FLAGS ?= -O3
+# TinyUSB defines
+CFLAGS += -DTUD_OPT_RP2040_USB_DEVICE_ENUMERATION_FIX=1 -DCFG_TUSB_MCU=OPT_MCU_RP2040 -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
+
+# option to override default optimization level, set in boards/$(BOARD)/mpconfigboard.mk
+CFLAGS += $(OPTIMIZATION_FLAGS)
+
+#Debugging/Optimization
+ifeq ($(DEBUG), 1)
+  CFLAGS += -ggdb3 -Og
+  # No LTO because we may place some functions in RAM instead of flash.
+else
+  CFLAGS += -DNDEBUG
+
+  # No LTO because we may place some functions in RAM instead of flash.
+
+  ifdef CFLAGS_BOARD
+    CFLAGS += $(CFLAGS_BOARD)
+  endif
+endif
+
+DISABLE_WARNINGS = -Wno-unused-function -Wno-unused-variable -Wno-strict-overflow -Wno-cast-align -Wno-strict-prototypes -Wno-nested-externs -Wno-double-promotion -Wno-sign-compare
+
+CFLAGS += $(INC) -Wall -Werror -std=gnu11 -nostdlib -fshort-enums $(BASE_CFLAGS) $(CFLAGS_MOD) $(COPT) $(DISABLE_WARNINGS)
+
+CFLAGS += \
+  -march=armv6-m \
+  -mthumb \
+	-mabi=aapcs-linux \
+	-mcpu=cortex-m0plus \
+	-msoft-float \
+	-mfloat-abi=soft
+
+PICO_LDFLAGS = --specs=nosys.specs -Wl,--wrap=__aeabi_ldiv0 -Wl,--wrap=__aeabi_idiv0 -Wl,--wrap=__aeabi_lmul -Wl,--wrap=__clzsi2 -Wl,--wrap=__clzdi2 -Wl,--wrap=__ctzsi2 -Wl,--wrap=__ctzdi2 -Wl,--wrap=__popcountsi2 -Wl,--wrap=__popcountdi2 -Wl,--wrap=__clz -Wl,--wrap=__clzl -Wl,--wrap=__clzll -Wl,--wrap=__aeabi_idiv -Wl,--wrap=__aeabi_idivmod -Wl,--wrap=__aeabi_ldivmod -Wl,--wrap=__aeabi_uidiv -Wl,--wrap=__aeabi_uidivmod -Wl,--wrap=__aeabi_uldivmod -Wl,--wrap=__aeabi_dadd -Wl,--wrap=__aeabi_ddiv -Wl,--wrap=__aeabi_dmul -Wl,--wrap=__aeabi_drsub -Wl,--wrap=__aeabi_dsub -Wl,--wrap=__aeabi_cdcmpeq -Wl,--wrap=__aeabi_cdrcmple -Wl,--wrap=__aeabi_cdcmple -Wl,--wrap=__aeabi_dcmpeq -Wl,--wrap=__aeabi_dcmplt -Wl,--wrap=__aeabi_dcmple -Wl,--wrap=__aeabi_dcmpge -Wl,--wrap=__aeabi_dcmpgt -Wl,--wrap=__aeabi_dcmpun -Wl,--wrap=__aeabi_i2d -Wl,--wrap=__aeabi_l2d -Wl,--wrap=__aeabi_ui2d -Wl,--wrap=__aeabi_ul2d -Wl,--wrap=__aeabi_d2iz -Wl,--wrap=__aeabi_d2lz -Wl,--wrap=__aeabi_d2uiz -Wl,--wrap=__aeabi_d2ulz -Wl,--wrap=__aeabi_d2f -Wl,--wrap=sqrt -Wl,--wrap=cos -Wl,--wrap=sin -Wl,--wrap=tan -Wl,--wrap=atan2 -Wl,--wrap=exp -Wl,--wrap=log -Wl,--wrap=ldexp -Wl,--wrap=copysign -Wl,--wrap=trunc -Wl,--wrap=floor -Wl,--wrap=ceil -Wl,--wrap=round -Wl,--wrap=sincos -Wl,--wrap=asin -Wl,--wrap=acos -Wl,--wrap=atan -Wl,--wrap=sinh -Wl,--wrap=cosh -Wl,--wrap=tanh -Wl,--wrap=asinh -Wl,--wrap=acosh -Wl,--wrap=atanh -Wl,--wrap=exp2 -Wl,--wrap=log2 -Wl,--wrap=exp10 -Wl,--wrap=log10 -Wl,--wrap=pow -Wl,--wrap=powint -Wl,--wrap=hypot -Wl,--wrap=cbrt -Wl,--wrap=fmod -Wl,--wrap=drem -Wl,--wrap=remainder -Wl,--wrap=remquo -Wl,--wrap=expm1 -Wl,--wrap=log1p -Wl,--wrap=fma -Wl,--wrap=__aeabi_fadd -Wl,--wrap=__aeabi_fdiv -Wl,--wrap=__aeabi_fmul -Wl,--wrap=__aeabi_frsub -Wl,--wrap=__aeabi_fsub -Wl,--wrap=__aeabi_cfcmpeq -Wl,--wrap=__aeabi_cfrcmple -Wl,--wrap=__aeabi_cfcmple -Wl,--wrap=__aeabi_fcmpeq -Wl,--wrap=__aeabi_fcmplt -Wl,--wrap=__aeabi_fcmple -Wl,--wrap=__aeabi_fcmpge -Wl,--wrap=__aeabi_fcmpgt -Wl,--wrap=__aeabi_fcmpun -Wl,--wrap=__aeabi_i2f -Wl,--wrap=__aeabi_l2f -Wl,--wrap=__aeabi_ui2f -Wl,--wrap=__aeabi_ul2f -Wl,--wrap=__aeabi_f2iz -Wl,--wrap=__aeabi_f2lz -Wl,--wrap=__aeabi_f2uiz -Wl,--wrap=__aeabi_f2ulz -Wl,--wrap=__aeabi_f2d -Wl,--wrap=sqrtf -Wl,--wrap=cosf -Wl,--wrap=sinf -Wl,--wrap=tanf -Wl,--wrap=atan2f -Wl,--wrap=expf -Wl,--wrap=logf -Wl,--wrap=ldexpf -Wl,--wrap=copysignf -Wl,--wrap=truncf -Wl,--wrap=floorf -Wl,--wrap=ceilf -Wl,--wrap=roundf -Wl,--wrap=sincosf -Wl,--wrap=asinf -Wl,--wrap=acosf -Wl,--wrap=atanf -Wl,--wrap=sinhf -Wl,--wrap=coshf -Wl,--wrap=tanhf -Wl,--wrap=asinhf -Wl,--wrap=acoshf -Wl,--wrap=atanhf -Wl,--wrap=exp2f -Wl,--wrap=log2f -Wl,--wrap=exp10f -Wl,--wrap=log10f -Wl,--wrap=powf -Wl,--wrap=powintf -Wl,--wrap=hypotf -Wl,--wrap=cbrtf -Wl,--wrap=fmodf -Wl,--wrap=dremf -Wl,--wrap=remainderf -Wl,--wrap=remquof -Wl,--wrap=expm1f -Wl,--wrap=log1pf -Wl,--wrap=fmaf -Wl,--wrap=memcpy -Wl,--wrap=memset -Wl,--wrap=__aeabi_memcpy -Wl,--wrap=__aeabi_memset -Wl,--wrap=__aeabi_memcpy4 -Wl,--wrap=__aeabi_memset4 -Wl,--wrap=__aeabi_memcpy8 -Wl,--wrap=__aeabi_memset8
+
+LDFLAGS = $(CFLAGS) $(PICO_LDFLAGS) -Wl,-T,link.ld -Wl,-Map=$@.map -Wl,-cref -Wl,--gc-sections
+
+# Use toolchain libm if we're not using our own.
+ifndef INTERNAL_LIBM
+LIBS += -lm
+endif
+
+LDFLAGS += -mthumb -mcpu=cortex-m0plus
+
+SRC_SDK := \
+	src/common/pico_sync/critical_section.c \
+	src/common/pico_sync/lock_core.c \
+	src/common/pico_sync/mutex.c \
+	src/common/pico_time/time.c \
+	src/common/pico_util/pheap.c \
+	src/rp2_common/hardware_adc/adc.c \
+	src/rp2_common/hardware_claim/claim.c \
+	src/rp2_common/hardware_clocks/clocks.c \
+	src/rp2_common/hardware_dma/dma.c \
+	src/rp2_common/hardware_flash/flash.c \
+	src/rp2_common/hardware_gpio/gpio.c \
+	src/rp2_common/hardware_i2c/i2c.c \
+	src/rp2_common/hardware_irq/irq.c \
+	src/rp2_common/hardware_pio/pio.c \
+	src/rp2_common/hardware_pll/pll.c \
+	src/rp2_common/hardware_spi/spi.c \
+	src/rp2_common/hardware_sync/sync.c \
+	src/rp2_common/hardware_timer/timer.c \
+	src/rp2_common/hardware_uart/uart.c \
+	src/rp2_common/hardware_watchdog/watchdog.c \
+	src/rp2_common/hardware_xosc/xosc.c \
+	src/rp2_common/pico_bootrom/bootrom.c \
+	src/rp2_common/pico_double/double_init_rom.c \
+	src/rp2_common/pico_fix/rp2040_usb_device_enumeration/rp2040_usb_device_enumeration.c \
+	src/rp2_common/pico_float/float_init_rom.c \
+	src/rp2_common/pico_float/float_math.c \
+	src/rp2_common/pico_multicore/multicore.c \
+	src/rp2_common/pico_platform/platform.c \
+	src/rp2_common/pico_printf/printf.c \
+	src/rp2_common/pico_runtime/runtime.c \
+	src/rp2_common/pico_stdio/stdio.c \
+
+SRC_SDK := $(addprefix sdk/, $(SRC_SDK))
+
+SRC_C += \
+	boards/$(BOARD)/board.c \
+	boards/$(BOARD)/pins.c \
+	bindings/rp2pio/StateMachine.c \
+	bindings/rp2pio/__init__.c \
+	common-hal/rp2pio/StateMachine.c \
+	common-hal/rp2pio/__init__.c \
+	background.c \
+	peripherals/pins.c \
+	fatfs_port.c \
+	lib/libc/string0.c \
+	lib/mp-readline/readline.c \
+	lib/oofatfs/ff.c \
+	lib/oofatfs/option/ccsbcs.c \
+	lib/timeutils/timeutils.c \
+	lib/tinyusb/src/portable/raspberrypi/rp2040/dcd_rp2040.c \
+	lib/tinyusb/src/portable/raspberrypi/rp2040/rp2040_usb.c \
+	lib/utils/buffer_helper.c \
+	lib/utils/context_manager_helpers.c \
+	lib/utils/interrupt_char.c \
+	lib/utils/pyexec.c \
+	lib/utils/stdout_helpers.c \
+	lib/utils/sys_stdio_mphal.c \
+	mphalport.c \
+	supervisor/shared/memory.c \
+
+SRC_COMMON_HAL_EXPANDED = $(addprefix shared-bindings/, $(SRC_COMMON_HAL)) \
+                          $(addprefix shared-bindings/, $(SRC_BINDINGS_ENUMS)) \
+                          $(addprefix common-hal/, $(SRC_COMMON_HAL))
+
+SRC_SHARED_MODULE_EXPANDED = $(addprefix shared-bindings/, $(SRC_SHARED_MODULE)) \
+                             $(addprefix shared-module/, $(SRC_SHARED_MODULE)) \
+                             $(addprefix shared-module/, $(SRC_SHARED_MODULE_INTERNAL))
+
+# There may be duplicates between SRC_COMMON_HAL_EXPANDED and SRC_SHARED_MODULE_EXPANDED,
+# because a few modules have files both in common-hal/ and shared-modules/.
+# Doing a $(sort ...) removes duplicates as part of sorting.
+SRC_COMMON_HAL_SHARED_MODULE_EXPANDED = $(sort $(SRC_COMMON_HAL_EXPANDED) $(SRC_SHARED_MODULE_EXPANDED))
+
+SRC_S = supervisor/$(CHIP_FAMILY)_cpu.s
+SRC_S_UPPER = bs2_default_padded_checksummed.S \
+              sdk/src/rp2_common/hardware_divider/divider.S \
+              sdk/src/rp2_common/hardware_irq/irq_handler_chain.S \
+              sdk/src/rp2_common/pico_bit_ops/bit_ops_aeabi.S \
+              sdk/src/rp2_common/pico_double/double_aeabi.S \
+              sdk/src/rp2_common/pico_double/double_v1_rom_shim.S \
+              sdk/src/rp2_common/pico_divider/divider.S \
+              sdk/src/rp2_common/pico_float/float_aeabi.S \
+              sdk/src/rp2_common/pico_float/float_v1_rom_shim.S \
+              sdk/src/rp2_common/pico_int64_ops/pico_int64_ops_aeabi.S \
+              sdk/src/rp2_common/pico_mem_ops/mem_ops_aeabi.S \
+              sdk/src/rp2_common/pico_standard_link/crt0.S \
+
+OBJ = $(PY_O) $(SUPERVISOR_O) $(addprefix $(BUILD)/, $(SRC_C:.c=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_SDK:.c=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_COMMON_HAL_SHARED_MODULE_EXPANDED:.c=.o))
+ifeq ($(INTERNAL_LIBM),1)
+OBJ += $(addprefix $(BUILD)/, $(SRC_LIBM:.c=.o))
+endif
+OBJ += $(addprefix $(BUILD)/, $(SRC_S:.s=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_S_UPPER:.S=.o))
+OBJ += $(addprefix $(BUILD)/, $(SRC_MOD:.c=.o))
+
+
+SRC_QSTR += $(SRC_C) $(SRC_SUPERVISOR) $(SRC_COMMON_HAL_EXPANDED) $(SRC_SHARED_MODULE_EXPANDED)
+
+all: $(BUILD)/firmware.uf2
+
+$(BUILD)/firmware.elf: $(OBJ) link.ld
+	$(STEPECHO) "LINK $@"
+	$(Q)$(CC) -o $@ $(LDFLAGS) $(OBJ)
+	$(Q)$(SIZE) $@ | $(PYTHON3) $(TOP)/tools/build_memory_info.py link.ld
+
+$(BUILD)/firmware.bin: $(BUILD)/firmware.elf
+	$(STEPECHO) "Create $@"
+	$(Q)$(OBJCOPY) -O binary $^ $@
+
+$(BUILD)/firmware.uf2: $(BUILD)/firmware.bin
+	$(STEPECHO) "Create $@"
+	$(Q)$(PYTHON3) $(TOP)/tools/uf2/utils/uf2conv.py -f 0xe48bff56 -b 0x10000000 -c -o $@ $^
+
+include $(TOP)/py/mkrules.mk
+
+# Print out the value of a make variable.
+# https://stackoverflow.com/questions/16467718/how-to-print-out-a-variable-in-makefile
+print-%:
+	@echo $* = $($*)

ports/raspberrypi/Makefile

@@ -0,0 +1,18 @@
+RP2040
+==================
+
+This port supports many development boards that utilize RP2040 chips. See
+https://circuitpython.org/downloads for all supported boards.
+
+
+Building
+--------
+
+For build instructions see this guide: https://learn.adafruit.com/building-circuitpython/
+
+
+Port Specific modules
+---------------------
+
+.. toctree::
+    ../../shared-bindings/rp2pio/index