From 9f036f663014f3687f9d166e560b62dbe0d5b911 Mon Sep 17 00:00:00 2001
From: Graham Edgecombe <gpe@grahamedgecombe.com>
Date: Thu, 7 Dec 2017 22:12:50 +0000
Subject: [PATCH] Add UART demo program

---
 progmem.s | 32 +++++++++++++++-----------------
 1 file changed, 15 insertions(+), 17 deletions(-)

diff --git a/progmem.s b/progmem.s
index 9966639..fce1015 100644
--- a/progmem.s
+++ b/progmem.s
@@ -1,20 +1,18 @@
-    li t0, 7
-    li t1, 3
-    li t2, 0
+# set baud rate to 9600
+    li t0, 0x00020000
+    li t1, 3750
+    sw t1, 0(t0)
 
-# t2 = t0 * t1
-mul:
-    beqz t0, mul_done
-    andi t3, t0, 1
-    beqz t3, mul_even
-    add t2, t2, t1
-mul_even:
-    srli t0, t0, 1
-    slli t1, t1, 1
-    j mul
+# read char from the UART
+    li t0, 0x00020008
+    li t1, 0x00010000
+loop:
+    lw t2, 0(t0)
+    bltz t2, loop
 
-# display results on the LEDs
-mul_done:
-    li t0, 0x00010000
+# write to the LEDs
     sw t2, 0(t0)
-    j .
+
+# echo back to the UART
+    sw t2, 0(t1)
+    j loop