diff --git a/arch/arm/src/lc823450/lc823450_allocateheap2.c b/arch/arm/src/lc823450/lc823450_allocateheap2.c
index 2cebe4ba0d9..5e33fbcb705 100644
--- a/arch/arm/src/lc823450/lc823450_allocateheap2.c
+++ b/arch/arm/src/lc823450/lc823450_allocateheap2.c
@@ -166,7 +166,7 @@ void up_allocate_heap(FAR void **heap_start, size_t *heap_size)
   /* Return the heap settings */
 
   *heap_start = (uintptr_t *)&_eronly; /* please see ld.script */
-  *heap_size  = SRAM1_END - (int)heap_start;
+  *heap_size  = SRAM1_END - (int)*heap_start;
 
   /* Colorize the heap for debug */
 
@@ -230,6 +230,14 @@ void up_allocate_kheap(FAR void **heap_start, size_t *heap_size)
 #if CONFIG_MM_REGIONS > 1
 void up_addregion(void)
 {
-# error "TODO"
+  FAR void *region_start;
+  size_t region_size;
+
+  /* NOTE: add 1KB to avoid conflicts of initial stack */
+
+  region_start = (uintptr_t *)&_ebss + 1024;
+  region_size  = 0x02040000 - (int)region_start;
+
+  umm_addregion(region_start, region_size);
 }
 #endif
diff --git a/configs/lc823450-xgevk/rndis/defconfig b/configs/lc823450-xgevk/rndis/defconfig
index 23a27696aa1..e3f46b5c0d6 100644
--- a/configs/lc823450-xgevk/rndis/defconfig
+++ b/configs/lc823450-xgevk/rndis/defconfig
@@ -52,9 +52,9 @@ CONFIG_I2CTOOL_MAXBUS=1
 CONFIG_I2C_RESET=y
 CONFIG_I2S=y
 CONFIG_INTELHEX_BINARY=y
-CONFIG_IOB_BUFSIZE=128
+CONFIG_IOB_BUFSIZE=64
 CONFIG_IOB_NBUFFERS=64
-CONFIG_IOB_NCHAINS=10
+CONFIG_IOB_NCHAINS=20
 CONFIG_LC823450_I2C0=y
 CONFIG_LC823450_I2C1=y
 CONFIG_LC823450_I2S0=y