Add Arduino Micro and Arduino Uno

src/board/arduino/mega2560/board.mk

@@ -1 +1,9 @@
 EC=atmega2560
+
+PORT=$(wildcard /dev/ttyACM*)
+
+console:
+	sudo tio -b 9600 $(PORT)
+
+flash: $(BUILD)/ec.ihx
+	sudo avrdude -v -v -p $(EC) -c wiring -P $(PORT) -b 115200 -D -U flash:w:$<:i

src/board/arduino/mega2560/main.c

@@ -6,9 +6,16 @@ void init(void) {
     uart_stdio_init(0, 9600);
 }
 
-void main(void) {
+int main(void) {
     init();
 
     printf("Hello from System76 EC for the Arduino Mega 2560!\n");
-    for (;;) {}
+    for (;;) {
+        int c = getchar();
+        if (c == '\r') {
+            putchar('\n');
+        } else if (c > 0) {
+            putchar(c);
+        }
+    }
 }