diff --git a/include/mgos_ota.h b/include/mgos_ota.h
index a1b7a91..c6c9458 100644
--- a/include/mgos_ota.h
+++ b/include/mgos_ota.h
@@ -6,8 +6,8 @@
 /*
  * OTA API.
  *
- * See https://mongoose-os.com/docs/mongoose-os/userguide/ota.md for more details about
- * Mongoose OS OTA mechanism.
+ * See https://mongoose-os.com/docs/mongoose-os/userguide/ota.md for more
+ * details about Mongoose OS OTA mechanism.
  */
 
 #pragma once
@@ -34,6 +34,7 @@ struct mgos_ota_file_info {
   char name[50];
   uint32_t size;
   uint32_t processed;
+  uint32_t crc32;
   /* Part that corresponds to this file (JSON). */
   struct mg_str part;
 };
diff --git a/include/mgos_ota_backend.h b/include/mgos_ota_backend.h
new file mode 100644
index 0000000..8cfba25
--- /dev/null
+++ b/include/mgos_ota_backend.h
@@ -0,0 +1,86 @@
+/*
+ * Copyright (c) 2014-2018 Cesanta Software Limited
+ * All rights reserved
+ *
+ * Updater backend interface.
+ * A way to implement custom functionality during OTA.
+ * NB: Update can be aborted at any moment, including after finalize
+ * (if one of the backends fails to finalize).
+ */
+
+#pragma once
+
+#include <stdint.h>
+
+#include "common/mbuf.h"
+#include "common/mg_str.h"
+
+#include "mgos_ota.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#ifndef MGOS_UPD_BE_DATA_CHUNK_SIZE
+#define MGOS_UPD_BE_DATA_CHUNK_SIZE 512
+#endif
+
+struct mgos_ota_be_ctx; /* Defined by backend implementation. */
+
+struct mgos_ota_backend_if {
+  /* Create updater context. */
+  struct mgos_ota_be_ctx *(*create_ctx)(void);
+  /* Get status message. */
+  const char *(*get_status_msg)(struct mgos_ota_be_ctx *ctx);
+  /*
+   * Process the firmware manifest.
+   * Manifest info will remain valid for the duration of the update (until
+   * free_ctx).
+   * If returned value is SKIP, this backend will not get any files and move
+   * straight to free_ctx.
+   */
+  enum mgos_ota_result (*begin)(struct mgos_ota_be_ctx *ctx,
+                                const struct mgos_ota_manifest_info *mi);
+  /*
+   * Begin processing a file from the update package.
+   * If returned value is SKIP, there won't be DATA or END calls.
+   */
+  enum mgos_ota_result (*file_begin)(struct mgos_ota_be_ctx *ctx,
+                                     const struct mgos_ota_file_info *fi);
+
+  /*
+   * Process a chunk of file data. Data will be delivered to this function in
+   * MGOS_UPD_BE_DATA_CHUNK_SIZE chunks.
+   * Return number of bytes processed (0 .. data.len)
+   * or < 0 for error. In case of error, message should be provided in
+   * status_msg.
+   */
+  int (*file_data)(struct mgos_ota_be_ctx *ctx,
+                   const struct mgos_ota_file_info *fi, struct mg_str data);
+
+  /*
+   * Finalize a file. Remainder of the data (if any) is passed,
+   * number of bytes of that data processed should be returned. The amount of
+   * data
+   * will be less than MGOS_UPD_BE_DATA_CHUNK_SIZE.
+   * Value equal to data.len is an indication of success,
+   * < 0 + ctx->status_msg on error.
+   */
+  int (*file_end)(struct mgos_ota_be_ctx *ctx,
+                  const struct mgos_ota_file_info *fi, struct mg_str data);
+
+  /*
+   * Finalize the update.
+   * Return >= 0 if ok, < 0 + ctx->status_msg on error.
+   */
+  enum mgos_ota_result (*finalize)(struct mgos_ota_be_ctx *ctx,
+                                   bool *need_reboot);
+
+  void (*free_ctx)(struct mgos_ota_be_ctx *ctx);
+};
+
+void mgos_ota_register_backend(const struct mgos_ota_backend_if *be_if);
+
+#ifdef __cplusplus
+}
+#endif
diff --git a/mos.yml b/mos.yml
index 51e5127..e3f57f7 100644
--- a/mos.yml
+++ b/mos.yml
@@ -3,7 +3,7 @@ description: OTA common bits
 type: lib
 version: 1.0
 
-platforms: [ cc3200, esp32, esp8266, stm32 ]
+platforms: [ cc3200, esp32, esp8266, rs14100, stm32 ]
 
 sources:
   - src
@@ -26,6 +26,17 @@ config_schema:
   - ["update.timeout", "i", 600, {title : "Update will be aborted if it does not finish within this time"}]
   - ["update.commit_timeout", "i", {title : "After applying update, wait for commit up to this long"}]
 
+conds:
+  - when: mos.platform == "rs14100"
+    apply:
+      libs:
+        - origin: https://github.com/mongoose-os-libs/bootloader
+
+  - when: mos.platform == "stm32"
+    apply:
+      libs:
+        - origin: https://github.com/mongoose-os-libs/bootloader
+
 tags:
   - c
   - core
diff --git a/mos_stm32.yml b/mos_stm32.yml
deleted file mode 100644
index e8d593e..0000000
--- a/mos_stm32.yml
+++ /dev/null
@@ -1,2 +0,0 @@
-libs:
-  - origin: https://github.com/mongoose-os-libs/bootloader