diff --git a/firmware/src/protocol.c b/firmware/src/protocol.c
index a6902d1..f80e0cb 100644
--- a/firmware/src/protocol.c
+++ b/firmware/src/protocol.c
@@ -14,7 +14,7 @@ LOG_MODULE_REGISTER(protocol, LOG_LEVEL_DBG);
 
 #define PROTOCOL_STACK_SIZE 2048
 #define PROTOCOL_PRIORITY 5
-#define BUFFER_SIZE 512
+#define BUFFER_SIZE 4096
 
 static uint8_t buffer[BUFFER_SIZE];
 static volatile uint32_t rx_index = 0;
@@ -25,6 +25,7 @@ static protocol_cmd_t current_command = CMD_INVALID;
 void send_ok()
 {
     const char *response = "OK\n";
+    LOG_DBG("Sending response: %s", response);
     usb_write_buffer((const uint8_t *)response, strlen(response));
 }
 
@@ -32,6 +33,7 @@ void send_error(int32_t error_code)
 {
     char response[32];
     snprintf(response, sizeof(response), "ERR %d\n", error_code);
+    LOG_DBG("Sending response: %s", response);
     usb_write_buffer((const uint8_t *)response, strlen(response));
 }
 
@@ -81,6 +83,7 @@ int put_binary_file(const char *filename, ssize_t filesize, uint32_t expected_cr
     ssize_t bytes_written = 0;
     uint32_t running_crc32 = 0;
     uint32_t retry_count = 0;
+    size_t accumulated = 0;
 
     fs_file_t_init(&file);
     LOG_DBG("Opening file '%s' for writing (expected size: %zd bytes, expected CRC32: 0x%08x)", filename, filesize, expected_crc32);
@@ -96,8 +99,11 @@ int put_binary_file(const char *filename, ssize_t filesize, uint32_t expected_cr
     uint32_t start = k_uptime_get_32();
     while (bytes_written < filesize)
     {
-        size_t to_write = MIN(sizeof(buffer), filesize - bytes_written);
-        ssize_t read = usb_read_buffer(buffer, to_write);
+        /* Nur so viel lesen, wie in den restlichen Puffer passt (oder bis zum Dateiende) */
+        size_t remaining_file = filesize - bytes_written - accumulated;
+        size_t to_read = MIN(sizeof(buffer) - accumulated, remaining_file);
+
+        ssize_t read = usb_read_buffer(buffer + accumulated, to_read);
 
         if (read < 0)
         {
@@ -109,15 +115,13 @@ int put_binary_file(const char *filename, ssize_t filesize, uint32_t expected_cr
         {
             if (retry_count >= 10)
             {
-                LOG_ERR("No data received from USB after multiple attempts (received %zd bytes, expected %zd bytes)", bytes_written, filesize);
+                LOG_ERR("No data received from USB after multiple attempts");
                 fs_close(&file);
                 return -ETIMEDOUT;
             }
 
             usb_resume_rx();
-            // LOG_DBG("No data available from USB, waiting for data... (attempt %u)", retry_count + 1);
-
-            if (bytes_written == 0)
+            if ((bytes_written + accumulated) == 0)
             {
                 usb_wait_for_data(K_SECONDS(30));
             }
@@ -129,30 +133,43 @@ int put_binary_file(const char *filename, ssize_t filesize, uint32_t expected_cr
             continue;
         }
 
-        ssize_t written = fs_write(&file, buffer, read);
-        //ssize_t written = read;
-        if (written < 0)
-        {
-            LOG_ERR("Error writing to file '%s': %d", filename, (int)written);
-            fs_close(&file);
-            return (int)written;
-        }
-        running_crc32 = crc32_ieee_update(running_crc32, buffer, written);
-
-        bytes_written += written;
+        /* Wir haben Daten bekommen: Zähler hochsetzen und USB weiterlauschen lassen */
+        accumulated += read;
         retry_count = 0;
         usb_resume_rx();
+
+        /* SCHREIBEN: Erst auf den Flash schreiben, wenn der Puffer voll ist (4096 Bytes)
+           ODER wenn wir das Ende der Datei erreicht haben. */
+        if (accumulated == sizeof(buffer) || (bytes_written + accumulated) == filesize)
+        {
+            ssize_t written = fs_write(&file, buffer, accumulated);
+            if (written < 0)
+            {
+                LOG_ERR("Error writing to file '%s': %d", filename, (int)written);
+                fs_close(&file);
+                return (int)written;
+            }
+
+            /* CRC erst nach dem erfolgreichen Block-Schreiben berechnen */
+            running_crc32 = crc32_ieee_update(running_crc32, buffer, accumulated);
+            bytes_written += accumulated;
+
+            /* Puffer für die nächste Runde leeren */
+            accumulated = 0;
+        }
     }
+
     uint32_t duration = k_uptime_get_32() - start;
-    uint32_t kb_per_s = (filesize * 1000) / (duration * 1024 +1);
+    uint32_t kb_per_s = (filesize * 1000) / (duration * 1024 + 1);
     LOG_DBG("Received file '%s' (%zd bytes) in %u ms (%u kb/s), CRC32: 0x%08x", filename, filesize, duration, kb_per_s, running_crc32);
     fs_close(&file);
-
+    LOG_DBG("Closed file '%s' after writing", filename);
     if (running_crc32 != expected_crc32)
     {
         LOG_ERR("CRC32 mismatch for file '%s': expected 0x%08x, got 0x%08x", filename, expected_crc32, running_crc32);
         return -EIO;
     }
+    LOG_DBG("File '%s' received successfully with matching CRC32", filename);
     return 0;
 }
 
diff --git a/firmware/src/usb.c b/firmware/src/usb.c
index 260ad9e..1a79342 100644
--- a/firmware/src/usb.c
+++ b/firmware/src/usb.c
@@ -118,9 +118,11 @@ void usb_write_buffer(const uint8_t *buf, size_t len)
         len -= written;
         buf += written;
 
+        uart_irq_tx_enable(cdc_dev);
+        
         if (len > 0)
         {
-            uart_irq_tx_enable(cdc_dev);
+
             if (k_sem_take(&usb_tx_sem, K_MSEC(100)) != 0)
             {
                 LOG_WRN("USB TX timeout - consumer not reading?");