atmega: add Emakefun RF-Nano V3.0 board

examples/microchip/atmega/build.zig

@@ -15,6 +15,7 @@ pub fn build(b: *std.Build) void {
     const available_examples = [_]Example{
         .{ .target = mb.ports.atmega.boards.arduino.nano, .name = "arduino-nano_blinky", .file = "src/blinky.zig" },
         .{ .target = mb.ports.atmega.boards.arduino.uno_rev3, .name = "arduino-uno_blinky", .file = "src/blinky.zig" },
+        .{ .target = mb.ports.atmega.boards.emakefun.rf_nano_v3, .name = "rf-nano-v3_blinky", .file = "src/blinky.zig" },
     };
 
     for (available_examples) |example| {

port/microchip/atmega/build.zig

@@ -16,6 +16,9 @@ boards: struct {
     adafruit: struct {
         itsybitsy_32u4: *const microzig.Target,
     },
+    emakefun: struct {
+        rf_nano_v3: *const microzig.Target,
+    },
 },
 
 pub fn init(dep: *std.Build.Dependency) ?Self {
@@ -99,6 +102,15 @@ pub fn init(dep: *std.Build.Dependency) ?Self {
                     },
                 }),
             },
+            .emakefun = .{
+                .rf_nano_v3 = chip_atmega328p.derive(.{
+                    .board = .{
+                        .name = "Emakefun RF-Nano V3.0",
+                        .url = "https://github.com/emakefun/rf-nano",
+                        .root_source_file = b.path("src/boards/rf_nano_v3.zig"),
+                    },
+                }),
+            },
         },
     };
 }

port/microchip/atmega/src/boards/rf_nano_v3.zig

@@ -0,0 +1,59 @@
+//! Emakefun RF-Nano V3.0: Arduino Nano V3.0 compatible board with an onboard
+//! nRF24L01+ (or Si24R1) wired to the hardware SPI bus.
+//!
+//! - Radio: CE = D7 (PD7), CS = D8 (PB0), SCK = D13 (PB5), HODI = D11 (PB3), HIDO = D12 (PB4).
+//! - The radio IRQ pin is not connected; poll the STATUS register instead.
+//! - The onboard LED shares D13 (PB5) with SCK, so it flickers with SPI traffic.
+//! - D7, D8, D11, D12 and D13 are used by the radio.
+//!
+//! Schematic: https://github.com/emakefun/rf-nano/blob/master/schematic/rf-nano_sch_v3.0.pdf
+
+pub const chip = @import("chip");
+
+pub const clock_frequencies = .{
+    .cpu = 16_000_000,
+};
+
+pub const pin_map = .{
+    // Port D
+    .D0 = "PD0",
+    .D1 = "PD1",
+    .D2 = "PD2",
+    .D3 = "PD3",
+    .D4 = "PD4",
+    .D5 = "PD5",
+    .D6 = "PD6",
+    .D7 = "PD7",
+
+    // Port B
+    .D8 = "PB0",
+    .D9 = "PB1",
+    .D10 = "PB2",
+    .D11 = "PB3",
+    .D12 = "PB4",
+    .D13 = "PB5",
+
+    // Port C (Analog)
+    .A0 = "PC0",
+    .A1 = "PC1",
+    .A2 = "PC2",
+    .A3 = "PC3",
+    .A4 = "PC4",
+    .A5 = "PC5",
+    .A6 = "ADC6",
+    .A7 = "ADC7",
+
+    // Onboard LED
+    .LED = "PB5",
+
+    // nRF24L01+ radio
+    .NRF_CE = "PD7",
+    .NRF_CS = "PB0",
+    .SCK = "PB5",
+    .HODI = "PB3",
+    .HIDO = "PB4",
+
+    // I2C (TWI)
+    .SDA = "PC4",
+    .SCL = "PC5",
+};