flake.nix

@@ -289,6 +289,10 @@
           path = ./templates/dev/rs-hello;
           description = "Rust hello world template.";
         };
+        stm32-blink = {
+          path = ./templates/dev/esp-blink;
+          description = "STM32G4 blink template with libopencm3.";
+        };
       };
     };
 }

templates/dev/stm32-blink/.envrc

@@ -0,0 +1 @@
+use flake

templates/dev/stm32-blink/.gitignore

@@ -0,0 +1,5 @@
+.cache/
+.direnv/
+build/
+compile_commands.json
+result

templates/dev/stm32-blink/Makefile

@@ -0,0 +1,67 @@
+PREFIX   ?= arm-none-eabi-
+CC        = $(PREFIX)gcc
+OBJCOPY   = $(PREFIX)objcopy
+SIZE      = $(PREFIX)size
+
+PNAME    := blink
+BUILD    := build
+
+# libopencm3 is provided by the Nix shell
+OPENCM3_DIR ?= ""
+
+SRCS     := src/main.c
+OBJS     := $(addprefix $(BUILD)/, $(SRCS:.c=.o))
+
+# STM32G4
+CPU_FLAGS := -mcpu=cortex-m4 -mthumb -mfloat-abi=hard -mfpu=fpv4-sp-d16
+
+CFLAGS   := $(CPU_FLAGS) \
+            -DSTM32G4 \
+            -Os -Wall -Wextra \
+            -ffunction-sections -fdata-sections \
+            -I$(OPENCM3_DIR)/include
+
+LDFLAGS  := $(CPU_FLAGS) \
+            -nostartfiles \
+            -Wl,--gc-sections \
+            -L$(OPENCM3_DIR)/lib \
+            -lopencm3_stm32g4
+
+ELF := $(BUILD)/$(PNAME).elf
+BIN := $(BUILD)/$(PNAME).bin
+HEX := $(BUILD)/$(PNAME).hex
+
+.PHONY: all clean flash size
+
+all: $(BIN) $(HEX) size
+
+$(BUILD)/%.o: %.c
+	@mkdir -p $(@D)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+LDSCRIPT := $(BUILD)/stm32g474xe.ld
+
+$(LDSCRIPT):
+	@mkdir -p $(@D)
+	$(CC) -I$(OPENCM3_DIR)/include $(shell python3 $(OPENCM3_DIR)/scripts/genlink.py $(OPENCM3_DIR)/ld/devices.data stm32g474xe DEFS) -P -E $(OPENCM3_DIR)/ld/linker.ld.S -o $@
+
+$(ELF): $(OBJS) $(LDSCRIPT)
+	$(CC) $(OBJS) $(LDFLAGS) -T$(LDSCRIPT) -o $@
+
+$(BIN): $(ELF)
+	$(OBJCOPY) -O binary $< $@
+
+$(HEX): $(ELF)
+	$(OBJCOPY) -O ihex $< $@
+
+size: $(ELF)
+	$(SIZE) $<
+
+flash: $(BIN)
+	openocd \
+	  -f interface/stlink.cfg \
+	  -f target/stm32g4x.cfg \
+	  -c "program $(BIN) verify reset exit 0x08000000"
+
+clean:
+	rm -rf $(BUILD)

templates/dev/stm32-blink/README.md

@@ -0,0 +1,28 @@
+# STM32G4 blink template
+
+Blinks the LD2 LED (PA5) on a [Nucleo-G474RE](https://www.st.com/en/evaluation-tools/nucleo-g474re.html) using [libopencm3](https://github.com/libopencm3/libopencm3).
+
+Set `BLINK_PORT` / `BLINK_PIN` for your board in [`src/main.c`](./src/main.c).
+
+## Toolchain
+
+The Nix dev shell provides:
+
+- `arm-none-eabi-gcc` (via `gcc-arm-embedded`)
+- `openocd` for flashing and debugging
+- `stlink` utilities (`st-flash`, `st-info`)
+- `libopencm3` built for `stm32/g4` (exposed as `$LIBOPENCM3_DIR`)
+
+## Build
+
+```bash
+make
+```
+
+## Flash
+
+```bash
+make flash
+```
+
+This uses OpenOCD with the built-in ST-Link interface config.

templates/dev/stm32-blink/build.sh

@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+make clean
+mkdir -p build
+bear -- make

templates/dev/stm32-blink/flake.nix

@@ -0,0 +1,161 @@
+{
+  description = "A blink template for STM32G4";
+
+  inputs = {
+    nixpkgs.url = "nixpkgs/nixpkgs-unstable";
+    utils.url = "github:numtide/flake-utils";
+    libopencm3-src = {
+      url = "github:libopencm3/libopencm3";
+      flake = false;
+    };
+    pre-commit-hooks = {
+      url = "github:cachix/pre-commit-hooks.nix";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    {
+      self,
+      nixpkgs,
+      utils,
+      libopencm3-src,
+      pre-commit-hooks,
+      ...
+    }:
+    {
+      overlays.default = final: prev: {
+        libopencm3-stm32 = final.stdenvNoCC.mkDerivation {
+          pname = "libopencm3-stm32";
+          version = "latest";
+
+          src = libopencm3-src;
+
+          postPatch = ''
+            patchShebangs scripts
+          '';
+
+          nativeBuildInputs = [
+            final.gcc-arm-embedded
+            final.python3
+            final.gnumake
+          ];
+
+          enableParallelBuilding = true;
+
+          makeFlags = [
+            "PREFIX=arm-none-eabi-"
+          ];
+
+          TARGETS = "stm32/f0 stm32/f1 stm32/f2 stm32/f3 stm32/f4 stm32/f7 stm32/l0 stm32/l1 stm32/l4 stm32/g0 stm32/g4 stm32/h7 stm32/u5";
+
+          installPhase = ''
+            runHook preInstall
+
+            mkdir -p $out
+            cp -r include lib mk scripts ld $out/
+
+            patchShebangs $out/scripts
+
+            runHook postInstall
+          '';
+
+          meta = with final.lib; {
+            description = "Open source ARM Cortex-M microcontroller library (STM32 targets)";
+            homepage = "http://libopencm3.org/";
+            license = licenses.lgpl3Plus;
+            platforms = platforms.all;
+          };
+        };
+      };
+    }
+    // utils.lib.eachDefaultSystem (
+      system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ self.overlays.default ];
+        };
+        pname = "blink";
+        version = "0.1.0";
+      in
+      {
+        packages = {
+          inherit (pkgs) libopencm3-stm32;
+          default = pkgs.stdenvNoCC.mkDerivation {
+            inherit pname version;
+            src = pkgs.lib.cleanSource ./.;
+
+            nativeBuildInputs = with pkgs; [
+              gcc-arm-embedded
+              gnumake
+              python3
+            ];
+
+            makeFlags = [
+              "OPENCM3_DIR=${pkgs.libopencm3-stm32}"
+              "PREFIX=arm-none-eabi-"
+            ];
+
+            installPhase = ''
+              runHook preInstall
+              mkdir -p $out/bin
+              cp build/${pname}.elf $out/bin/
+              cp build/${pname}.bin $out/bin/
+              cp build/${pname}.hex $out/bin/
+              runHook postInstall
+            '';
+          };
+        };
+
+        devShells.default =
+          let
+            # FIXME: 'gnu/stubs-32.h' file not found
+            clangdWrapper = pkgs.writeShellScriptBin "clangd" ''
+              exec ${pkgs.clang-tools}/bin/clangd \
+                --query-driver=${pkgs.gcc-arm-embedded}/bin/arm-none-eabi-* \
+                "$@"
+            '';
+          in
+          pkgs.mkShell {
+            name = "stm32-blink";
+            packages = self.packages.${system}.default.nativeBuildInputs ++ [
+              clangdWrapper
+
+              pkgs.bear
+              pkgs.openocd
+              pkgs.stlink
+            ];
+            OPENCM3_DIR = pkgs.libopencm3-stm32;
+            PREFIX = "arm-none-eabi-";
+          };
+
+        formatter =
+          let
+            inherit (self.checks.${system}.pre-commit-check.config) package configFile;
+            script = ''
+              ${pkgs.lib.getExe package} run --all-files --config ${configFile}
+            '';
+          in
+          pkgs.writeShellScriptBin "pre-commit-run" script;
+
+        checks = {
+          build-packages = pkgs.linkFarm "flake-packages-${system}" self.packages.${system};
+
+          pre-commit-check = pre-commit-hooks.lib.${system}.run {
+            src = ./.;
+            hooks = {
+              nixfmt.enable = true;
+              clang-format = {
+                enable = true;
+                types_or = pkgs.lib.mkForce [
+                  "c"
+                  "c++"
+                ];
+              };
+            };
+          };
+        };
+      }
+    );
+}

templates/dev/stm32-blink/src/main.c

@@ -0,0 +1,50 @@
+#include <libopencm3/cm3/systick.h>
+#include <libopencm3/stm32/gpio.h>
+#include <libopencm3/stm32/rcc.h>
+
+/* Nucleo-G474RE: LD2 is on PA5 */
+#define BLINK_PORT GPIOA
+#define BLINK_PIN GPIO5
+#define BLINK_PERIOD_MS 1000
+
+static volatile uint32_t s_ticks = 0;
+
+void sys_tick_handler(void) { s_ticks++; }
+
+static void delay_ms(uint32_t ms) {
+  uint32_t until = s_ticks + ms;
+  while (s_ticks < until)
+    ;
+}
+
+static void clock_setup(void) {
+  rcc_clock_setup_pll(&rcc_hsi_configs[RCC_CLOCK_3V3_170MHZ]);
+}
+
+static void systick_setup(void) {
+  /* 1 ms tick at 170 MHz core clock */
+  systick_set_reload(rcc_ahb_frequency / 1000 - 1);
+  systick_set_clocksource(STK_CSR_CLKSOURCE_AHB);
+  systick_counter_enable();
+  systick_interrupt_enable();
+}
+
+static void gpio_setup(void) {
+  rcc_periph_clock_enable(RCC_GPIOA);
+  gpio_mode_setup(BLINK_PORT, GPIO_MODE_OUTPUT, GPIO_PUPD_NONE, BLINK_PIN);
+  gpio_set_output_options(BLINK_PORT, GPIO_OTYPE_PP, GPIO_OSPEED_LOW,
+                          BLINK_PIN);
+}
+
+int main(void) {
+  clock_setup();
+  systick_setup();
+  gpio_setup();
+
+  while (1) {
+    gpio_toggle(BLINK_PORT, BLINK_PIN);
+    delay_ms(BLINK_PERIOD_MS);
+  }
+
+  return 0;
+}