diff --git a/part7-bluetooth/Makefile b/part7-bluetooth/Makefile
index 44bd023..143c51b 100644
--- a/part7-bluetooth/Makefile
+++ b/part7-bluetooth/Makefile
@@ -1,7 +1,7 @@
 CFILES = $(wildcard *.c)
 OFILES = $(CFILES:.c=.o)
 LLVMPATH = /opt/homebrew/opt/llvm/bin
-GCCFLAGS = -Wall -O0 -ffreestanding -nostdinc -nostdlib -mcpu=cortex-a72+nosimd
+GCCFLAGS = -Wall -O2 -ffreestanding -nostdinc -nostdlib -mcpu=cortex-a72+nosimd
 
 all: clean kernel8.img
 
diff --git a/part7-bluetooth/bt.c b/part7-bluetooth/bt.c
index 7d148fe..800f5b4 100644
--- a/part7-bluetooth/bt.c
+++ b/part7-bluetooth/bt.c
@@ -1,7 +1,7 @@
 #include "io.h"
 #include "fb.h"
 
-unsigned char *params = (unsigned char *)SAFE_ADDRESS;
+volatile unsigned char *params = (unsigned char *)SAFE_ADDRESS;
 
 // UART0
 
@@ -93,7 +93,7 @@ enum {
 
 unsigned char empty[] = {};
 
-int hciCommandBytes(unsigned char *opcodebytes, unsigned char *data, unsigned char length)
+int hciCommandBytes(volatile unsigned char *opcodebytes, volatile unsigned char *data, unsigned char length)
 {
     unsigned char c=0;
 
@@ -130,7 +130,7 @@ int hciCommandBytes(unsigned char *opcodebytes, unsigned char *data, unsigned ch
     return 0;
 }
 
-int hciCommand(unsigned short ogf, unsigned short ocf, unsigned char *data, unsigned char length)
+int hciCommand(unsigned short ogf, unsigned short ocf, volatile unsigned char *data, unsigned char length)
 {
     unsigned short opcode = ogf << 10 | ocf;
     unsigned char opcodebytes[2] = { lo(opcode), hi(opcode) };