uart: add ledctrl app

uart/led.h

@@ -0,0 +1,3 @@
+#define LED_ADDR ((volatile char*)0xC000)
+
+#define led_write(x) (*LED_ADDR = (x))

uart/ledctrl.c

@@ -0,0 +1,24 @@
+#include "led.h"
+#include "uart.h"
+
+int main() {
+  int c;
+  int led = 0;
+
+  while (1) {
+    led_write(1 << led);
+    c = uart_read();
+
+    if (c == 'a') {
+      led++;
+    } else if (c == 'd') {
+      led--;
+    }
+
+    if (led == 8) {
+      led = 0;
+    } else if (led < 0) {
+      led = 7;
+    }
+  }
+}

uart/makefile

@@ -0,0 +1,15 @@
+CC = ../bin/cc
+LD = ../bin/ld
+
+all: echo.vhdl.inc ledctrl.vhdl.inc
+
+echo.vhdl.inc: echo.o uart.o
+ledctrl.vhdl.inc: ledctrl.o uart.o
+
+%.vhdl.inc:
+	$(LD) -o $@ --vhdl $^
+
+PHONY: clean
+
+clean:
+	rm -rf *.o *.vhdl.inc

uart/util.c

@@ -0,0 +1,11 @@
+#define CYCLES_PER_MS 6666  // ish
+
+/** waits a general amount of time */
+void busy_sleep(int ms) {
+  for (int i = 0; i < ms; ++i) {
+    // wait for 1 ms
+    for (int i = 0; i < CYCLES_PER_MS; ++i) {
+      // nothing
+    }
+  }
+}

uart/util.h

@@ -0,0 +1,2 @@
+/** waits a general amount of time */
+void busy_sleep(int ms);