fix a problem with end. make uartputc() wait until h/w is ready.

1 files changed, 3 insertions, 0 deletions

diff --git a/uart.c b/uart.c
index 29f6df4..35fac1b 100644
--- a/uart.c
+++ b/uart.c
@@ -46,6 +46,9 @@ uartinit(void)
 void
 uartputc(int c)
 {
+  // wait for Transmit Holding Empty to be set in LSR.
+  while((*R(5) & (1 << 5)) == 0)
+    ;
   *R(0) = c;
 }