diff --git a/.gitignore b/.gitignore
index 9b46ad2f..6955ac55 100644
--- a/.gitignore
+++ b/.gitignore
@@ -65,6 +65,10 @@ tools/keytools/x64
 tools/keytools/Debug
 tools/keytools/Release
 
+# delta binaries
+tools/delta/bmdiff
+tools/delta/bmpatch
+
 # Vim swap files
 .*.swp
 
diff --git a/Makefile b/Makefile
index d02b654f..88581b05 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ include tools/config.mk
 ## Initializers
 WOLFBOOT_ROOT?=$(PWD)
 CFLAGS:=-D"__WOLFBOOT"
-CFLAGS+=-Werror
+CFLAGS+=-Werror -Wextra
 LSCRIPT:=config/target.ld
 LDFLAGS:=
 LD_START_GROUP:=-Wl,--start-group
diff --git a/include/uart_drv.h b/include/uart_drv.h
new file mode 100644
index 00000000..c250b499
--- /dev/null
+++ b/include/uart_drv.h
@@ -0,0 +1,32 @@
+/* uart_drv.h
+ *
+ * The HAL API definitions for UART driver extension.
+ *
+ * Copyright (C) 2021 wolfSSL Inc.
+ *
+ * This file is part of wolfBoot.
+ *
+ * wolfBoot is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * wolfBoot is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1335, USA
+ */
+
+#ifndef H_HAL_UART_
+#define H_HAL_UART_
+
+#include <stdint.h>
+int uart_tx(const uint8_t c);
+int uart_rx(uint8_t *c);
+int uart_init(uint32_t bitrate, uint8_t data, char parity, uint8_t stop);
+
+#endif /* H_HAL_UART_ */
diff --git a/include/uart_flash.h b/include/uart_flash.h
index 566d16b5..11b38c55 100644
--- a/include/uart_flash.h
+++ b/include/uart_flash.h
@@ -31,15 +31,14 @@
 #ifndef UART_FLASH_DRI_H
 #define UART_FLASH_DRI_H
 #include <stdint.h>
+#include "uart_drv.h"
 
 #ifdef UART_FLASH
     #ifndef UART_FLASH_BITRATE
       #define UART_FLASH_BITRATE 460800
     #endif
-    int uart_init(uint32_t bitrate, uint8_t data, char parity, uint8_t stop);
     void uart_send_current_version(void);
 #else
-    #define uart_init(...) (-1)
     #define uart_send_current_version() do{}while(0)
 #endif /* UART_FLASH */
 
diff --git a/src/delta.c b/src/delta.c
index 28f1400f..ad142aa4 100644
--- a/src/delta.c
+++ b/src/delta.c
@@ -171,7 +171,7 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
         pa_start = (WOLFBOOT_SECTOR_SIZE + 1) * page_start;
         pa = ctx->src_a + pa_start;
         while (((uint32_t)(pa - ctx->src_a) < ctx->size_a ) && (p_off < len)) {
-            if ((ctx->size_a - (pa - ctx->src_a)) < BLOCK_HDR_SIZE)
+            if ((uint32_t)(ctx->size_a - (pa - ctx->src_a)) < BLOCK_HDR_SIZE)
                 break;
             if ((ctx->size_b - ctx->off_b) < BLOCK_HDR_SIZE)
                 break;
@@ -214,7 +214,7 @@ int wb_diff(WB_DIFF_CTX *ctx, uint8_t *patch, uint32_t len)
             while (((uint32_t)(pb - ctx->src_b) < pb_end) && (p_off < len)) {
                 if ((ctx->size_b - ctx->off_b) < BLOCK_HDR_SIZE)
                     break;
-                if (ctx->size_b - (pb - ctx->src_b) < BLOCK_HDR_SIZE)
+                if ((uint32_t)(ctx->size_b - (pb - ctx->src_b)) < BLOCK_HDR_SIZE)
                     break;
                 if (WOLFBOOT_SECTOR_SIZE > (pb - ctx->src_b) - (page_start * WOLFBOOT_SECTOR_SIZE))
                     break;
diff --git a/test-app/app_stm32wb.c b/test-app/app_stm32wb.c
index b6cefbb8..753a8692 100644
--- a/test-app/app_stm32wb.c
+++ b/test-app/app_stm32wb.c
@@ -27,6 +27,7 @@
 #include "led.h"
 #include "hal.h"
 #include "wolfboot/wolfboot.h"
+#include "uart_drv.h"
 
 #ifdef PLATFORM_stm32wb
 char enc_key[] = "0123456789abcdef0123456789abcdef" /* ChaCha key (256 bit) */
diff --git a/tools/delta/Makefile b/tools/delta/Makefile
index 0a2b0b56..e7c446a1 100644
--- a/tools/delta/Makefile
+++ b/tools/delta/Makefile
@@ -1,6 +1,5 @@
 all: bmdiff bmpatch
-
-
+CFLAGS+=-Wall -Werror -Wextra
 bmdiff: delta.o bmdiff.o
 	gcc -o bmdiff delta.o bmdiff.o
 
@@ -10,10 +9,10 @@ bmpatch: delta.o bmdiff.o
 lib: delta.o
 
 delta.o:
-	gcc -c -o delta.o ../../src/delta.c -I../../include -ggdb
+	gcc -c -o delta.o ../../src/delta.c -I../../include -ggdb $(CFLAGS)
 
 bmdiff.o:
-	gcc -c -o bmdiff.o bmdiff.c -I../../include -ggdb
+	gcc -c -o bmdiff.o bmdiff.c -I../../include -ggdb $(CFLAGS)
 
 clean:
 	rm -f bmpatch bmdiff delta.o
diff --git a/tools/delta/bmdiff.c b/tools/delta/bmdiff.c
index e8ecec12..59e2e456 100644
--- a/tools/delta/bmdiff.c
+++ b/tools/delta/bmdiff.c
@@ -56,11 +56,12 @@ int main(int argc, char *argv[])
         return 244;
     }
     if ((argc != 4) && (mode == MODE_DIFF)) {
-            printf("Usage: %s file1 file2 patch\n");
+            printf("Usage: %s file1 file2 patch\n", argv[0]);
             exit(2);
     }
     if ((argc != 3) && (mode == MODE_PATCH)) {
-        printf("Usage: %s file patch (WARNING: patching is done in place and it will overwrite the original source.)\n");
+        printf("Usage: %s file patch (WARNING: patching is done in place and it"
+                "will overwrite the original source.)\n", argv[0]);
         exit(2);
     }
 
diff --git a/tools/keytools/Makefile b/tools/keytools/Makefile
index 6e4854c0..12640cac 100644
--- a/tools/keytools/Makefile
+++ b/tools/keytools/Makefile
@@ -2,7 +2,8 @@
 
 CC      = gcc
 WOLFDIR = ../../lib/wolfssl/
-CFLAGS  = -Wall -I. -DWOLFSSL_USER_SETTINGS -I$(WOLFDIR) -I../../include
+CFLAGS  = -Wall -Wextra -Werror
+CFLAGS  += -I. -DWOLFSSL_USER_SETTINGS -I$(WOLFDIR) -I../../include
 
 # option variables
 DEBUG_FLAGS     = -g -DDEBUG -DDEBUG_SIGNTOOL -DDEBUG_WOLFSSL -DDEBUG_WOLFSSL_VERBOSE