diff --git a/flake.nix b/flake.nix
index 10be19d..257aafe 100644
--- a/flake.nix
+++ b/flake.nix
@@ -327,7 +327,7 @@
           lib = pkgs.lib;
           avr = pkgs.pkgsCross.avr.buildPackages;
         in pkgs.stdenv.mkDerivation rec {
-          name = "prime-tx";
+          name = "radio-rx";
           src = ./.;
 
           buildInputs = [
@@ -353,6 +353,39 @@
             '';
         };
 
+      packages."x86_64-linux"."interrupts-standalone" = (packages."x86_64-linux"."interrupts" atmega32u4);
+
+      packages."x86_64-linux"."interrupts" =
+        { mcu, chip_select, f_cpu }:
+        let
+          pkgs = import nixpkgs { system = "x86_64-linux"; };
+          lib = pkgs.lib;
+          avr = pkgs.pkgsCross.avr.buildPackages;
+        in pkgs.stdenv.mkDerivation rec {
+          name = "interrupts";
+          src = ./.;
+
+          buildInputs = [
+            (packages."x86_64-linux"."base" { inherit mcu chip_select f_cpu; })
+            (packages."x86_64-linux"."shift-register" { inherit mcu chip_select f_cpu; })
+            (packages."x86_64-linux"."display" { inherit mcu chip_select f_cpu; })
+          ];
+
+          CFLAGS = cflags { inherit mcu chip_select f_cpu; };
+          INCLUDE_DIRS = pkgs.lib.concatStringsSep " " (map (dir: "-I${dir}") buildInputs);
+          OBJECT_FILES = pkgs.lib.concatStringsSep " " (map (dir: "${dir}/*.o") buildInputs);
+
+          buildPhase = ''
+            ${avr.gcc}/bin/avr-gcc ${CFLAGS} ${INCLUDE_DIRS} -o main.o -c ${src}/interrupts/main.c
+            ${avr.gcc}/bin/avr-gcc ${CFLAGS} -o interrupts.elf main.o ${OBJECT_FILES}
+            $OBJCOPY -O ihex interrupts.elf interrupts.hex
+            '';
+          installPhase = ''
+            mkdir $out
+            cp interrupts.elf interrupts.hex $out
+            '';
+        };
+
       devShell."x86_64-linux" =
         let
           pkgs = import nixpkgs { system = "x86_64-linux"; };
diff --git a/interrupts/main.c b/interrupts/main.c
new file mode 100644
index 0000000..ea384e8
--- /dev/null
+++ b/interrupts/main.c
@@ -0,0 +1,65 @@
+#include <base.h>
+#include <display.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <avr/sleep.h>
+#include <avr/interrupt.h>
+
+dio_t light = { .ddr = &DDRC, .port = &PORTC, .pin = &PINC, .addr = 7 };
+dio_t interrupt_line = { .ddr = &DDRD, .port = &PORTD, .pin = &PIND, .addr = 2 };
+
+bool button_values[4] = { false, false, false, false };
+dio_t buttons[4] = {
+    { .ddr = &DDRD, .port = &PORTD, .pin = &PIND, .addr = 6 },
+    { .ddr = &DDRB, .port = &PORTB, .pin = &PINB, .addr = 7 },
+    { .ddr = &DDRB, .port = &PORTB, .pin = &PINB, .addr = 6 },
+    { .ddr = &DDRB, .port = &PORTB, .pin = &PINB, .addr = 5 },
+};
+
+
+ISR(INT2_vect) {
+    dio_set(&light, 1);
+    for (int i = 0; i < 4; i++) {
+        button_values[i] = dio_read(&buttons[i]);
+    }
+}
+
+void display_buttons(display_t *display) {
+    char msg[16];
+
+    snprintf(msg, 16, ": %d %d %d %d", button_values[0], button_values[1], button_values[2], button_values[3]);
+    display_clear(display);
+    display_write_message(display, msg);
+}
+
+int main(void) {
+    EIMSK = 1 << INT2;
+    EICRA |= 1 << ISC21 | 1 << ISC20;
+
+    display_t display = {
+        .reg = {
+            .output         = { .ddr = &DDRF, .port = &PORTF, .pin = &PINF, .addr = 7 },
+            .shift_clock    = { .ddr = &DDRF, .port = &PORTF, .pin = &PINF, .addr = 6 },
+            .latch_clock    = { .ddr = &DDRF, .port = &PORTF, .pin = &PINF, .addr = 5 },
+        }
+    };
+    display_init(&display);
+
+    dio_set_direction(&light, LINE_OUT);
+    dio_set_direction(&interrupt_line, LINE_IN);
+    for (int i = 0; i < 4; i++) {
+        dio_set_direction(&buttons[i], LINE_IN);
+    }
+
+    set_sleep_mode(SLEEP_MODE_IDLE);
+    while (1) {
+        display_buttons(&display);
+        dio_set(&light, 0);
+
+        sei();
+        sleep_mode();
+        cli();
+    }
+
+    return 0;
+}