1 files changed, 21 insertions, 0 deletions
diff --git a/stm32/app/i2c.c b/stm32/app/i2c.c
new file mode 100644
index 0000000..8c5630e
--- /dev/null
+++ b/stm32/app/i2c.c
@@ -0,0 +1,21 @@
+#include "project.h"
+
+static int mutex = 0;
+
+int
+i2c_lock (void)
+{
+  if (__sync_add_and_fetch (&mutex, 1) != 1) {
+    __sync_sub_and_fetch (&mutex, 1);
+    return -1;
+  }
+
+  return 0;
+}
+
+
+void
+i2c_unlock (void)
+{
+  __sync_sub_and_fetch (&mutex, 1);
+}