diff --git a/sbus-to-ztex-gateware-migen/blit.c b/sbus-to-ztex-gateware-migen/blit.c
index 088cf6e..168fa56 100644
--- a/sbus-to-ztex-gateware-migen/blit.c
+++ b/sbus-to-ztex-gateware-migen/blit.c
@@ -5,8 +5,14 @@
 */
 
 
-#define HRES 1280 // FIXME : should be generated
+#ifndef HRES
+#define HRES 1280
+#warning "Using default HRES"
+#endif
+#ifndef VRES
 #define VRES 1024
+#warning "Using default VRES"
+#endif
 #define BASE_FB   0x8FE00000 // FIXME : should be generated ; 2+ MiB of SDRAM as framebuffer
 
 #define BASE_ROM 0x00410000 // FIXME : should be generated ; 4-64 KiB of Wishbone ROM ? ; also in the LDS file ; also in the Vex config
@@ -369,7 +375,7 @@ struct cg6_fbc {
 void from_reset(void) __attribute__ ((noreturn)); // nothrow, 
 
 static inline void flush_cache(void) {
-	//asm volatile(".word 0x0000500F\n"); // flush the Dcache so that we get updated data
+	asm volatile(".word 0x0000500F\n"); // flush the Dcache so that we get updated data
 }
 
 typedef unsigned int unsigned_param_type;
diff --git a/sbus-to-ztex-gateware-migen/blit.sh b/sbus-to-ztex-gateware-migen/blit.sh
index abe81f8..298db35 100755
--- a/sbus-to-ztex-gateware-migen/blit.sh
+++ b/sbus-to-ztex-gateware-migen/blit.sh
@@ -1,5 +1,8 @@
 #!/bin/bash -x
 
+HRES=${1:-1280}
+VRES=${2:-1024}
+
 GCCDIR=~/LITEX/riscv64-unknown-elf-gcc-10.1.0-2020.08.2-x86_64-linux-ubuntu14
 GCCPFX=riscv64-unknown-elf-
 GCCLINK=${GCCDIR}/bin/${GCCPFX}gcc
@@ -17,8 +20,8 @@ OPT=-Os #-fno-inline
 ARCH=rv32i_zba_zbb_zbt
 
 if test "x$1" != "xASM"; then
-	$GCC $OPT -S -o blit.s -march=$ARCH -mabi=ilp32 -mstrict-align -fno-builtin-memset -nostdlib -ffreestanding -nostartfiles blit.c
+	$GCC $OPT -S -o blit.s -DHRES=${HRES} -DVRES=${VRES} -march=$ARCH -mabi=ilp32 -mstrict-align -fno-builtin-memset -nostdlib -ffreestanding -nostartfiles blit.c
 fi
-$GCC     $OPT -c -o blit.o -march=$ARCH -mabi=ilp32 -mstrict-align -fno-builtin-memset -nostdlib -ffreestanding -nostartfiles blit.s &&
-$GCCLINK $OPT    -o blit   -march=$ARCH -mabi=ilp32 -T blit.lds  -nostartfiles blit.o &&
+$GCC     $OPT -c -o blit.o -DHRES=${HRES} -DVRES=${VRES} -march=$ARCH -mabi=ilp32 -mstrict-align -fno-builtin-memset -nostdlib -ffreestanding -nostartfiles blit.s &&
+$GCCLINK $OPT    -o blit   -DHRES=${HRES} -DVRES=${VRES} -march=$ARCH -mabi=ilp32 -T blit.lds  -nostartfiles blit.o &&
 $OBJCOPY  -O binary -j .text -j .rodata blit blit.raw