Replace pico-blink build.sh (#110)

Removes the legacy build.sh script used to build the pico-blink firmware
and replaces it with a makefile leveraging SwiftPM + a new pico.json
toolset file. This means we no longer have to handle build flags in the
build script directly and SwiftPM can handle invoking the linker.

Author: rauhul

Tools/Toolsets/pico.json

@@ -0,0 +1,26 @@
+{
+    "schemaVersion": "1.0",
+    "swiftCompiler": {
+      "extraCLIOptions": [
+        "-Xfrontend", "-disable-stack-protector",
+        "-enable-experimental-feature", "Embedded",
+        "-Xcc", "-mcpu=cortex-m0plus"
+      ]
+    },
+    "linker": {
+      "extraCLIOptions": [
+        "-arch", "armv6m",
+        "-dead_strip",
+        "-static",
+        "-e", "_reset",
+        "-no_zero_fill_sections",
+        "-segalign", "4",
+        "-segaddr", "__RESET", "0x20000000",
+        "-segaddr", "__VECTORS", "0x20000100",
+        "-seg1addr", "0x20000200",
+        "-pagezero_size", "0",
+        "-allow_dead_duplicates"
+      ]
+    }
+  }
+  

pico-blink/Makefile

@@ -0,0 +1,61 @@
+##===----------------------------------------------------------------------===##
+##
+## This source file is part of the Swift open source project
+##
+## Copyright (c) 2025 Apple Inc. and the Swift project authors.
+## Licensed under Apache License v2.0 with Runtime Library Exception
+##
+## See https://swift.org/LICENSE.txt for license information
+##
+##===----------------------------------------------------------------------===##
+
+# Paths
+REPOROOT         := $(shell git rev-parse --show-toplevel)
+TOOLSROOT        := $(REPOROOT)/Tools
+TOOLSET          := $(TOOLSROOT)/Toolsets/pico.json
+MACHO2UF2        := $(TOOLSROOT)/macho2uf2.py
+SWIFT_BUILD      := swift build
+
+# Flags
+PICO_FAMILY      := rp2040
+ARCH             := armv6m
+TARGET           := $(ARCH)-apple-none-macho
+SWIFT_BUILD_ARGS := \
+	--configuration release \
+	--triple $(TARGET) \
+	--toolset $(TOOLSET) \
+	--disable-local-rpath
+BUILDROOT        := $(shell $(SWIFT_BUILD) $(SWIFT_BUILD_ARGS) --show-bin-path)
+
+.PHONY: build
+build:
+	@echo "building..."
+	$(SWIFT_BUILD) \
+		$(SWIFT_BUILD_ARGS) \
+		-Xlinker -map -Xlinker $(BUILDROOT)/Application.mangled.map \
+		--verbose
+
+	@echo "demangling linker map..."
+	cat $(BUILDROOT)/Application.mangled.map \
+		| c++filt | swift demangle > $(BUILDROOT)/Application.map
+
+	@echo "disassembling..."
+	otool \
+		-arch $(ARCH) -v -V -d -t \
+		$(BUILDROOT)/Application \
+		| c++filt | swift demangle > $(BUILDROOT)/Application.disassembly
+
+	@echo "extracting binary..."
+	$(MACHO2UF2) \
+		--pico-family "$(PICO_FAMILY)" \
+		"$(BUILDROOT)/Application" \
+		"$(BUILDROOT)/Application.uf2" \
+		--base-address 0x20000000 \
+		--segments '__TEXT,__DATA,__VECTORS,__RESET'
+
+
+.PHONY: clean
+clean:
+	@echo "cleaning..."
+	@swift package clean
+	@rm -rf .build

pico-blink/Package.swift

@@ -5,11 +5,10 @@ import PackageDescription
 let package = Package(
   name: "RP2040",
   products: [
-    .library(name: "Blinky", type: .static, targets: ["Blinky"])
+    .executable(name: "Application", targets: ["Application"])
   ],
   targets: [
-    .target(name: "Blinky", dependencies: ["RP2040"]),
+    .executableTarget(name: "Application", dependencies: ["RP2040"]),
     .target(name: "Support"),
     .target(name: "RP2040", dependencies: ["Support"]),
-  ]
-)
+  ])

pico-blink/README.md

@@ -11,9 +11,11 @@
 - Connect the Pico board via a USB cable to your Mac, and make sure it's in the USB Mass Storage firmware upload mode (either hold the BOOTSEL button while plugging the board, or make sure your Flash memory doesn't contain any valid firmware).
 - Make sure you have a recent nightly Swift toolchain that has Embedded Swift support.
 - Build and copy the program in the UF2 format to the Mass Storage device to trigger flashing the program into memory (after which the device will reboot and run the firmware):
+
 ``` console
 $ cd pico-blink
-$ TOOLCHAINS='<toolchain-identifier>' ./build.sh
-$ cp .build/blink.uf2 /Volumes/RP2040
+$ make
+$ cp .build/Application.uf2 /Volumes/RP2040
 ```
+
 - The green LED should now be blinking in a pattern.

pico-blink/Sources/Blinky/Blinky.swift renamed to pico-blink/Sources/Application/Application.swift

@@ -12,7 +12,7 @@
 import RP2040
 
 @main
-struct Main {
+struct Application {
   // swift-format-ignore: NeverUseImplicitlyUnwrappedOptionals
   static var board: RP2040! = nil
 

pico-blink/build.sh

@@ -2,7 +2,7 @@
 ##
 ## This source file is part of the Swift open source project
 ##
-## Copyright (c) 2023 Apple Inc. and the Swift project authors.
+## Copyright (c) 2025 Apple Inc. and the Swift project authors.
 ## Licensed under Apache License v2.0 with Runtime Library Exception
 ##
 ## See https://swift.org/LICENSE.txt for license information