Code rewritten without Arduino.h

src/avr_asm_lib/avr_asm_lib.ino

@@ -1,28 +1,28 @@
 // Copyright 2021 KoroLion (https://github.com/KoroLion)
 
 extern "C" {
-  void lm35_init(uint8_t port);
-  uint8_t lm35_read();
+  void lm35_init(unsigned char port);
+  unsigned char lm35_read();
 
   void led_init();
   void led_enable();
   void led_disable();
 }
 
-void setup() {
-  Serial.begin(9600);
+const unsigned char LED_TEMP = 30;
 
-  lm35_init(A3);
+int main() {
+  lm35_init(17);
   led_init();
-}
 
-void loop() {
-  uint8_t t = lm35_read();
-  if (t >= 30) {
-    led_enable();
-  } else {
-    led_disable();
+  while (true) {
+    unsigned char t = lm35_read();
+    if (t >= LED_TEMP) {
+      led_enable();
+    } else {
+      led_disable();
+    }
   }
 
-  Serial.println(t);
+  return 0;
 }