Add ATtiny port with avr25 CPU support and fix AVR vector tables by mattnite · Pull Request #923 · ZigEmbeddedGroup/microzig

mattnite · 2026-03-21T09:03:29Z

Add a new port for Microchip ATtiny (ATtiny85, ATtiny84) with HAL, board definitions (Digispark, Adafruit Trinket, Adafruit Gemma), and blinky examples including an interrupt handler example.

Also fix the AVR startup logic for both avr25 and avr5:

Place vector table in microzig_flash_start section so it lands at address 0x0 where the hardware expects it
Emit full vector table with entries for all interrupt vectors, not just the reset vector
Add InterruptOptions so users can specify interrupt handlers via microzig_options, which get wired into the vector table
Update calling convention names for zig 0.15.2 compatibility (.avr_signal/.avr_interrupt/.auto, .@"fn")

Grazfather · 2026-04-28T21:07:20Z

+const gpio = microzig.hal.gpio;
+
+// ATtiny84: use PA0 as the LED pin
+const led_pin = gpio.pin(.a, 0);


can't we put this in the board config so that we can use the same blinky.zig for multiple boards?

mattnite

Feels like there's a lot of duplication in the cpu files, will have to comb through and trim it down.

mattnite · 2026-05-19T05:44:49Z

 };

+/// AVR interrupt handler function type.
+pub const HandlerFn = *const fn () callconv(.avr_signal) void;


not sure if this should actually be avr_signal

mattnite · 2026-05-19T05:46:24Z

+    });
+}
+
+fn make_isr_handler(comptime name: []const u8, comptime func: anytype) type {


is this a duplicate?

mattnite · 2026-05-19T05:47:57Z

                    .name = "avr5",
                    .root_source_file = mb.core_dep.namedLazyPath("cpu_avr5"),
                };
+            } else if (std.mem.eql(u8, target.cpu.model.name, "avr25")) {


let's start looking at making a table instead of if elses.

Add a new port for Microchip ATtiny (ATtiny85, ATtiny84) with HAL, board definitions (Digispark, Adafruit Trinket, Adafruit Gemma), and blinky examples including an interrupt handler example. Also fix the AVR startup logic for both avr25 and avr5: - Place vector table in microzig_flash_start section so it lands at address 0x0 where the hardware expects it - Emit full vector table with entries for all interrupt vectors, not just the reset vector - Add InterruptOptions so users can specify interrupt handlers via microzig_options, which get wired into the vector table - Update calling convention names for zig 0.15.2 compatibility (.avr_signal/.avr_interrupt/.auto, .@"fn") Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

mattnite

More comments and verifications that need to be made before merging

mattnite · 2026-05-19T21:36:11Z

+
+pub const microzig_options: microzig.Options = .{
+    .interrupts = .{
+        .INT0 = &my_int0_handler,


I don't see any configuration in the main function for this, consider removing the example it if it's unverified.

mattnite · 2026-05-19T21:37:05Z

@@ -0,0 +1,16 @@
+const microzig = @import("microzig");


TODO: Double check

mattnite · 2026-05-19T21:37:14Z

@@ -0,0 +1,18 @@
+const microzig = @import("microzig");


TODO: double check

mattnite · 2026-05-19T21:37:20Z

@@ -0,0 +1,20 @@
+const microzig = @import("microzig");


TODO: double check

mattnite · 2026-05-19T21:37:45Z

+const microzig = @import("microzig");
+const cpu = microzig.cpu;
+
+pub const gpio = struct {


TODO: review ATtiny84 datasheet/family reference.

mattnite · 2026-05-19T21:40:26Z

+
+    const atpack = b.dependency("atpack", .{});
+
+    const avr25_target: std.Target.Query = .{


Shouldn't we be getting this from the cpu?

mattnite · 2026-05-19T21:40:55Z

+                .atdf = atpack.path("atdf/ATtiny85.atdf"),
+            },
+            .memory_regions = &.{
+                .{ .tag = .flash, .offset = 0x000000, .length = 8 * 1024, .access = .rx },


TODO: Double check memory

mattnite · 2026-05-19T21:41:05Z

+                .atdf = atpack.path("atdf/ATtiny84.atdf"),
+            },
+            .memory_regions = &.{
+                .{ .tag = .flash, .offset = 0x000000, .length = 8 * 1024, .access = .rx },


TODO: double check memory

mattnite · 2026-05-19T21:41:43Z

+
+    return .{
+        .chips = .{
+            .attiny85 = chip_attiny85.derive(.{}),


Why aren't we just assigning these? it should be safe to do that.

mattnite · 2026-05-19T21:42:10Z

+            .attiny85 = chip_attiny85.derive(.{}),
+            .attiny84 = chip_attiny84.derive(.{}),
+        },
+        .boards = .{


None of these boards use chip_attiny84.

mattnite force-pushed the attiny branch from 4d76f3c to 0568e7c Compare April 28, 2026 03:04

Grazfather reviewed Apr 28, 2026

View reviewed changes

mattnite force-pushed the attiny branch 2 times, most recently from d24d37b to 9ab36bb Compare May 19, 2026 05:01

mattnite commented May 19, 2026

View reviewed changes

mattnite and others added 6 commits May 19, 2026 14:33

Remove unused chips.zig from attiny port

236d464

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Remove unused imports from ATtiny HAL files

226c002

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Import cleanup

8f61c67

Declare led pin at board layer

65a7307

Remove unused imports

9ef8c9a

mattnite commented May 19, 2026

View reviewed changes

mattnite force-pushed the attiny branch from d596238 to 9ef8c9a Compare May 19, 2026 21:43

mattnite added 3 commits May 19, 2026 16:22

Remove deprecated boards (afaict)

c4f6ddb

Just blinky for trinket

79dfbac

Yes, you do need to derive

4913644


		const atpack = b.dependency("atpack", .{});

		const avr25_target: std.Target.Query = .{

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