From e8dbb77db5d1d0f2641e31ab823f6202226774d8 Mon Sep 17 00:00:00 2001
From: Dominic Clifton <me@dominicclifton.name>
Date: Sat, 13 Dec 2014 19:45:02 +0000
Subject: [PATCH] UART1 - Fix interrupt race condition which resulted in UART
 randomly stopping transmission of data.

---
 src/main/drivers/serial_uart.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/src/main/drivers/serial_uart.c b/src/main/drivers/serial_uart.c
index e192415f7b..663c9ff455 100644
--- a/src/main/drivers/serial_uart.c
+++ b/src/main/drivers/serial_uart.c
@@ -254,9 +254,11 @@ uint8_t uartRead(serialPort_t *instance)
 void uartWrite(serialPort_t *instance, uint8_t ch)
 {
     uartPort_t *s = (uartPort_t *)instance;
-    s->port.txBuffer[s->port.txBufferHead++] = ch;
-    if (s->port.txBufferHead >= s->port.txBufferSize) {
+    s->port.txBuffer[s->port.txBufferHead] = ch;
+    if (s->port.txBufferHead + 1 >= s->port.txBufferSize) {
         s->port.txBufferHead = 0;
+    } else {
+        s->port.txBufferHead++;
     }
 
     if (s->txDMAChannel) {