Fixes #28, verify bootloader message

Author: Bas Visscher

ESPTool/Communication/Communicator.cs

@@ -1,7 +1,10 @@
 using EspDotNet.Config;
 using Microsoft.Extensions.Logging;
 using System;
+using System.Diagnostics;
 using System.IO.Ports;
+using System.Text.RegularExpressions;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;
 
@@ -122,6 +125,12 @@ public async Task ExecutePinSequence(List<PinSequenceStep> sequence, Cancellatio
             }
         }
 
+        public async Task<int> ReadRawAsync(byte[] buffer, CancellationToken token)
+        {
+            return await _serialPort.BaseStream.ReadAsync(buffer, 0, buffer.Length, token);
+        }
+
+
         /// <summary>
         /// Disposes the serial port and associated resources.
         /// </summary>

ESPTool/Tools/BootloaderTool.cs

@@ -1,6 +1,8 @@
 using EspDotNet.Communication;
 using EspDotNet.Config;
 using EspDotNet.Loaders.ESP32BootLoader;
+using System.Text.RegularExpressions;
+using System.Text;
 
 namespace EspDotNet.Tools
 {
@@ -20,6 +22,10 @@ public async Task<ESP32BootLoader> StartAsync(CancellationToken token = default)
             // Start bootloader
             await _communicator.ExecutePinSequence(_bootloaderSequence, token);
 
+            // Check bootloader message
+            if (!await TryReadBootStartup(token))
+                throw new Exception("Booloader message not verified");
+
             // Instantiate loader and synchronize
             var bootloader = new ESP32BootLoader(_communicator);
 
@@ -29,6 +35,21 @@ public async Task<ESP32BootLoader> StartAsync(CancellationToken token = default)
             return bootloader;
         }
 
+        private async Task<bool> TryReadBootStartup(CancellationToken token)
+        {
+            var buffer = new byte[4096];
+            var read = await _communicator.ReadRawAsync(buffer, token);
+            if (read > 0)
+            {
+                var data = new byte[read];
+                Array.Copy(buffer, data, read);
+                Regex regex = new Regex("boot:(0x[0-9a-fA-F]+)(.*waiting for download)?");
+                var result = regex.Match(Encoding.ASCII.GetString(data));
+                return result.Success;
+            }
+            return false;
+        }
+
         private async Task<bool> Synchronize(ESP32BootLoader loader, CancellationToken token)
         {
             for (int tryNo = 0; tryNo < 100; tryNo++)