Reorganize drivers and utility modules into lib/ subdirectory and update server and upload scripts

lib/download_util.py

@@ -0,0 +1,68 @@
+import os
+import urequests
+from sd_util import SDCardManager
+
+def download_file(url, dest_filename, use_sd=True):
+    """Downloads a file from a URL over the network in memory-efficient chunks.
+    
+    If use_sd is True, it automatically mounts the microSD card and saves to /sd/dest_filename.
+    Otherwise, it saves to the local flash storage.
+    
+    Returns:
+        str: The full path to the downloaded file on success, None on failure.
+    """
+    dest_path = dest_filename
+    sd_manager = None
+    
+    if use_sd:
+        sd_manager = SDCardManager(mount_point='/sd')
+        if not sd_manager.mount():
+            print("Download Error: Could not mount SD card.")
+            return None
+        dest_path = f"/sd/{dest_filename}"
+        
+    print(f"Starting download from: {url} -> {dest_path}")
+    
+    try:
+        res = urequests.get(url, stream=True)
+    except Exception as e:
+        print(f"HTTP Connection failed: {e}")
+        return None
+        
+    if res.status_code != 200:
+        print(f"HTTP Error: Received status code {res.status_code}")
+        res.close()
+        return None
+        
+    try:
+        # Read from socket stream in chunks to avoid OutOfMemory errors
+        chunk_size = 4096
+        total_downloaded = 0
+        
+        with open(dest_path, 'wb') as f:
+            while True:
+                # Read chunk from the raw socket connection stream
+                chunk = res.raw.read(chunk_size)
+                if not chunk:
+                    break
+                f.write(chunk)
+                total_downloaded += len(chunk)
+                
+                # Dynamic logging
+                if total_downloaded % (chunk_size * 25) == 0:
+                     print(f"Downloaded {total_downloaded // 1024} KB...")
+                     
+        print(f"Download complete! Saved {total_downloaded} bytes to '{dest_path}'.")
+        return dest_path
+        
+    except Exception as e:
+        print(f"Error writing to file: {e}")
+        # Clean up partial file on failure
+        try:
+            os.remove(dest_path)
+        except:
+            pass
+        return None
+        
+    finally:
+        res.close()