diff --git a/Makefile b/Makefile
index 6000ee8f..b9deaced 100644
--- a/Makefile
+++ b/Makefile
@@ -94,14 +94,10 @@ test-app/image_v1_signed.bin: test-app/image.bin
 	@echo "\t[SIGN] $(BOOT_IMG)"
 	$(Q)$(SIGN_TOOL) $(SIGN_OPTIONS) $(BOOT_IMG) $(PRIVATE_KEY) 1
 
-factory.bin: $(BOOT_IMG) wolfboot-align.bin $(PRIVATE_KEY) test-app/image_v1_signed.bin
+factory.bin: $(BOOT_IMG) wolfboot-align.bin $(PRIVATE_KEY) test-app/image_v1_signed.bin $(BINASSEMBLE)
 	@echo "\t[MERGE] $@"
-	$(Q)$(OBJCOPY) --set-start=$(ARCH_OFFSET) \
-		--add-section .signed_image=test-app/image_v1_signed.bin \
-		--change-section-vma .signed_image=$(WOLFBOOT_PARTITION_BOOT_ADDRESS) \
-		--set-section-flags .signed_image=alloc,readonly \
-		wolfboot.elf factory.elf
-	$(Q)$(OBJCOPY) --gap-fill=255 -O binary factory.elf $@
+	$(Q)$(BINASSEMBLE) $@ $(ARCH_FLASH_OFFSET) wolfboot-align.bin \
+                              $(WOLFBOOT_PARTITION_BOOT_ADDRESS) test-app/image_v1_signed.bin
 
 wolfboot.elf: include/target.h $(OBJS) $(LSCRIPT) FORCE
 	@echo "\t[LD] $@"
diff --git a/tools/bin-assemble/Makefile b/tools/bin-assemble/Makefile
new file mode 100644
index 00000000..8c2288d8
--- /dev/null
+++ b/tools/bin-assemble/Makefile
@@ -0,0 +1,11 @@
+CC=gcc
+CFLAGS=-Wall -g -ggdb
+EXE=bin-assemble
+
+LIBS=
+
+$(EXE): $(EXE).o
+	$(CC) -o $@ $^ $(CFLAGS) $(LIBS)
+
+clean:
+	rm -f *.o $(EXE)
diff --git a/tools/bin-assemble/bin-assemble.c b/tools/bin-assemble/bin-assemble.c
new file mode 100644
index 00000000..610b11f6
--- /dev/null
+++ b/tools/bin-assemble/bin-assemble.c
@@ -0,0 +1,205 @@
+/* bin-assemble.c
+ *
+ * Copyright (C) 2006-2020 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 02110-1301, USA
+ *
+ *=============================================================================
+ *
+ * assemble binary parts based on address
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <errno.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <unistd.h>
+#include <string.h>
+
+#define BLOCK_SZ 1024
+
+void usage(const char* execname)
+{
+    fprintf(stderr,
+            "%s output [<address> <input>]\n"
+            "assemble binary parts with addresses",
+            execname);
+    exit(1);
+}
+
+typedef struct {
+    const char* fname;
+    size_t      address;
+    size_t      nbytes;
+} binentry_t;
+
+int binentry_address_compare(const void* a, const void* b)
+{
+    const binentry_t* ba = (const binentry_t*)a;
+    const binentry_t* bb = (const binentry_t*)b;
+
+    if (ba->address < bb->address) {
+        return -1;
+    } else if (ba->address > bb->address) {
+        return 1;
+    } else {
+        return 0;
+    }
+}
+
+
+int main(int argc, const char* argv[]) {
+    const char* outname = NULL;
+    size_t i = 0;
+    size_t num_entries = 0;
+    binentry_t* entries = NULL;
+    size_t cur_add = 0;
+    char fill = '\xff';
+    size_t nr = 0;
+    size_t nw = 0;
+    char data[BLOCK_SZ];
+    int err = 0;
+
+    /* require at least 1 input file */
+    if (argc < 4 || (argc % 2) != 0) {
+        usage(argv[0]);
+    }
+
+    outname = argv[1];
+    num_entries = (argc - 2) / 2;
+
+    entries = malloc( sizeof(binentry_t) * num_entries);
+    if (entries == NULL) {
+        fprintf(stderr, "unable to allocate %zu entries\n;", num_entries);
+        return EXIT_FAILURE;
+    }
+
+    for (i=0; i<num_entries; i++) {
+        char* endptr = NULL;
+        struct stat st;
+
+        entries[i].address = strtol(argv[2*i + 2], &endptr, 0);
+        if (*endptr) {
+            fprintf(stderr,
+                    "Remaining characters in adderss field %s\n", endptr);
+        }
+        entries[i].fname = argv[2*i + 3];
+
+        if (stat(entries[i].fname, &st)) {
+            fprintf(stderr, "unable to stat %s: %s\n", entries[i].fname,
+                    strerror(errno));
+            return EXIT_FAILURE;
+        }
+
+        entries[i].nbytes = st.st_size;
+
+#if VERBOSE
+        printf("%s %zu %zu\n",
+               entries[i].fname,
+               entries[i].address,
+               entries[i].nbytes);
+#endif
+    }
+
+    qsort(entries, num_entries, sizeof(binentry_t), binentry_address_compare);
+
+    // check for overlap
+    for (i=1; i<num_entries; i++) {
+        size_t endaddr = entries[i-1].address + entries[i-1].nbytes;
+        if (endaddr > entries[i].address) {
+            fprintf(stderr,
+              "overlap with %s(end address 0x%zx) and %s (start address 0x%zx \n",
+                    entries[i-1].fname, endaddr,
+                    entries[i].fname, entries[i].address);
+            err = 1;
+        }
+        if (err) {
+            return err;
+        }
+
+    }
+
+    // TODO: consider handling stdout "-"
+
+    FILE* fo = fopen(outname, "wb");
+    if (fo == NULL){
+        fprintf(stderr, "opening %s failed %s\n",
+                outname, strerror(errno));
+        return EXIT_FAILURE;
+    }
+
+    cur_add = entries[0].address;
+    for (i=0; i<num_entries; i++) {
+        FILE* fi = fopen(entries[i].fname, "rb");
+        if (fi == NULL){
+            fprintf(stderr, "opening %s failed %s\n",
+                    entries[i].fname, strerror(errno));
+            return EXIT_FAILURE;
+        }
+
+        /* fill until address */
+        while(cur_add < entries[i].address) {
+            nw = fwrite(&fill, 1, 1, fo);
+            if (nw != 1) {
+                fprintf(stderr,
+                  "Failed to write fill bytes at 0x%zu\n",
+                        cur_add);
+                return EXIT_FAILURE;
+            }
+
+            cur_add++;
+        }
+
+        while (!feof(fi)) {
+            nr = fread(data, 1, BLOCK_SZ, fi);
+            nw = fwrite(data, 1, nr, fo);
+            cur_add += nw;
+            if (nr != nw) {
+                fprintf(stderr,
+                  "Failed to wrote %zu bytes of the %zu bytes read from %s\n",
+                        nw, nr, entries[i].fname);
+                return EXIT_FAILURE;
+            }
+
+            if (ferror(fi)) {
+                fprintf(stderr,
+                        "error reading from %s\n",
+                        entries[i].fname);
+                return EXIT_FAILURE;
+            }
+
+            if (ferror(fo)) {
+                fprintf(stderr,
+                        "error writing to %s\n",
+                        entries[i].fname);
+                return EXIT_FAILURE;
+            }
+
+        }
+
+
+        fclose(fi);
+    }
+
+    fclose(fo);
+
+    return 0;
+}
diff --git a/tools/test.mk b/tools/test.mk
index 6e60ee9d..401767a1 100644
--- a/tools/test.mk
+++ b/tools/test.mk
@@ -1,6 +1,7 @@
 TEST_UPDATE_VERSION?=2
 WOLFBOOT_VERSION?=0
 EXPVER=tools/test-expect-version/test-expect-version
+BINASSEMBLE=tools/bin-assemble/bin-assemble
 SPI_CHIP=SST25VF080B
 SPI_OPTIONS=SPI_FLASH=1 WOLFBOOT_PARTITION_SIZE=0x80000 WOLFBOOT_PARTITION_UPDATE_ADDRESS=0x00000 WOLFBOOT_PARTITION_SWAP_ADDRESS=0x80000
 SIGN_ARGS=
@@ -49,7 +50,10 @@ ifeq ($(HASH),SHA3)
 endif
 
 $(EXPVER):
-	make -C tools/test-expect-version
+	$(MAKE) -C $(dir $@)
+
+$(BINASSEMBLE):
+	$(MAKE) -C $(dir $@)
 
 # Testbed actions
 #