1 files changed, 4 insertions, 4 deletions
diff --git a/libmaple/usb/usb_callbacks.c b/libmaple/usb/usb_callbacks.c
index 08d62c5..5c4a386 100644
--- a/libmaple/usb/usb_callbacks.c
+++ b/libmaple/usb/usb_callbacks.c
@@ -32,10 +32,10 @@ USB_Line_Coding line_coding = {
 };
 
 uint8 vcomBufferRx[VCOM_RX_EPSIZE];
-uint8 countTx    = 0;
-uint8 recvBufIn  = 0;
-uint8 recvBufOut = 0;
-uint8 maxNewBytes   = VCOM_RX_EPSIZE;
+volatile uint8 countTx    = 0;
+volatile uint8 recvBufIn  = 0;
+volatile uint8 recvBufOut = 0;
+volatile uint8 maxNewBytes   = VCOM_RX_EPSIZE;
 
 RESET_STATE reset_state = START;