Add material for generating yotta module
diff --git a/yotta/data/entropy_hardware_poll.c b/yotta/data/entropy_hardware_poll.c
new file mode 100644
index 0000000..54e96c2
--- /dev/null
+++ b/yotta/data/entropy_hardware_poll.c
@@ -0,0 +1,52 @@
+/*
+ * Temporary "entropy" collector for Cortex-M4
+ *
+ * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
+ *
+ * This file is part of mbed TLS (https://tls.mbed.org)
+ */
+
+/*
+ * WARNING: this is a temporary hack!
+ * 1. Currently does not provide strong entropy, should be replaced to use the
+ * on-board hardware RNG (see IOTSSL-303)
+ * 2. This should be in a separete yotta module which would be a target
+ * dependency of mbedtls (see IOTSSL-313)
+ */
+
+#if defined(TARGET_LIKE_CORTEX_M4)
+
+#include "MK64F12.h"
+#include "core_cm4.h"
+#include <string.h>
+
+unsigned long hardclock( void )
+{
+ static int dwt_started = 0;
+
+ if( dwt_started == 0 )
+ {
+ CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
+ DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
+ }
+
+ return( DWT->CYCCNT );
+}
+
+int mbedtls_hardware_poll( void *data,
+ unsigned char *output, size_t len, size_t *olen )
+{
+ unsigned long timer = hardclock();
+ ((void) data);
+ *olen = 0;
+
+ if( len < sizeof(unsigned long) )
+ return( 0 );
+
+ memcpy( output, &timer, sizeof(unsigned long) );
+ *olen = sizeof(unsigned long);
+
+ return( 0 );
+}
+
+#endif