diff --git a/lib/stm32/f1/can.c b/lib/stm32/f1/can.c
index 9bd23cb3..2131fd1e 100644
--- a/lib/stm32/f1/can.c
+++ b/lib/stm32/f1/can.c
@@ -313,3 +313,16 @@ void can_receive(u32 canport, u8 fifo, bool release, u32 *id, bool *ext,
 	if (release)
 		can_fifo_release(CAN1, 0);
 }
+
+bool can_available_mailbox(u32 canport)
+{
+	if ((CAN_TSR(canport) & CAN_TSR_TME0) == CAN_TSR_TME0) {
+		return true;
+	} else if ((CAN_TSR(canport) & CAN_TSR_TME1) == CAN_TSR_TME1) {
+		return true;
+	} else if ((CAN_TSR(canport) & CAN_TSR_TME2) == CAN_TSR_TME2) {
+		return true;
+	} else {
+		return false;
+	}
+}