1 files changed, 42 insertions, 0 deletions
diff --git a/examples/minimal.zig b/examples/minimal.zig
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--- /dev/null
+++ b/examples/minimal.zig
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+//! The floor: the smallest thing that can boot on this chip and prove it is alive.
+//! No printing, no descriptor text - just a pin that toggles. Build it with
+//!   zig build -Dapp=examples/minimal.zig size
+
+const std = @import("std");
+const config = @import("config");
+const soc = @import("soc");
+
+/// Even the floor needs a panic handler: the default one formats and would pull in half of std.
+pub const panic = std.debug.FullPanic(struct {
+    fn call(_: []const u8, _: ?usize) noreturn {
+        while (true) {}
+    }
+}.call);
+const led: u6 = @intCast(config.led_pin);
+
+export fn zig_main() noreturn {
+    soc.gpio.configureOutput(led);
+    while (true) {
+        soc.gpio.setHigh(led);
+        soc.rom.ets_delay_us(100_000);
+        soc.gpio.setLow(led);
+        soc.rom.ets_delay_us(100_000);
+    }
+}
+
+export fn _start() linksection(".text.entry") callconv(.naked) noreturn {
+    asm volatile (
+        \\ li t0, 1 << 13
+        \\ csrs mstatus, t0
+        \\ la sp, __stack_top
+        \\ la t0, __bss_start
+        \\ la t1, __bss_end
+        \\ bgeu t0, t1, 2f
+        \\1:
+        \\ sw zero, 0(t0)
+        \\ addi t0, t0, 4
+        \\ bltu t0, t1, 1b
+        \\2:
+        \\ j zig_main
+    );
+}