Added an init packet which (for recent DFU OTA protocols) must transferred before the firmware image.

dist/dfu.js

@@ -132,6 +132,17 @@
         });
     }
     
+    /**
+     * Contains basic functionality for performing safety checks on software updates for nRF5 based devices.
+     * Init packet used for pre-checking to ensure the following image is compatible with the device.
+     * Contains information on device type, revision, and supported SoftDevices along with a CRC or hash of firmware image.
+     * 
+     * Not used in mbed bootloader.
+     */
+    function generateInitPacket() {
+        return new Uint8Array([0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0x01, 0x00, 0xFE, 0xFF, 0x00, 0x00]); // Temporary init packet.
+    }
+
     function provision(device, arrayBuffer, imageType) {
         return new Promise(function(resolve, reject) {
             log('function provision(device, arrayBuffer, imageType)');
@@ -289,11 +300,11 @@
 
                     var req_opcode = view.getUint8(1);
                     if (req_opcode === 1 && majorVersion > 6) {
-                        log('write null init packet');
+                        log('write init packet');
 
                         controlChar.writeValue(new Uint8Array([2,0]))
                         .then(() => {
-                            return packetChar.writeValue(new Uint8Array([0]));
+                            return packetChar.writeValue(generateInitPacket());
                         })
                         .then(() => {
                             return controlChar.writeValue(new Uint8Array([2,1]));

example_web.html

@@ -14,6 +14,7 @@
 
     <script>
         var urlMask = "//thegecko.github.io/web-bluetooth-dfu/firmware/NRF51822_{0}_Rob_OTA.hex";
+        var urlMask52 = "https://raw.githubusercontent.com/mjdietzx/web-bluetooth-dfu/develop/firmware/ble_app_hrs_with_dfu_nrf52.hex";
         var resultsEl = document.getElementById("results");
 
         function log(message) {
@@ -35,7 +36,8 @@
 
         function transfer(device) {
             return new Promise(function(resolve, reject) {
-                var url = urlMask.replace("{0}", device.name === "Hi_Rob" ? "Bye" : "Hi");
+                //var url = urlMask.replace("{0}", device.name === "Hi_Rob" ? "Bye" : "Hi");
+                var url = urlMask52; // nRF52832 application (example BLE heart rate from Nordic SDK) for DFU OTA update.
 
                 download(url)
                 .then(hex => {