Save debug log even when no SCSI requests are coming in

Normally we wait for the STATUS phase to be able to save
log file without disturbing SCSI processing. But this can
cause the very last log messages not be saved to file.

This commit changes behavior only when debug log is enabled.
Log will be saved after 2 seconds when no new SCSI requests are coming.
Shouldn't affect functional behavior, but to limit any performance impacts it is
limited to debug mode.

src/BlueSCSI.cpp

@@ -626,6 +626,7 @@ extern "C" void bluescsi_setup(void)
 extern "C" void bluescsi_main_loop(void)
 {
   static uint32_t sd_card_check_time = 0;
+  static uint32_t last_request_time = 0;
 
   platform_reset_watchdog();
 
@@ -643,9 +644,15 @@ extern "C" void bluescsi_main_loop(void)
     scsiLogPhaseChange(scsiDev.phase);
 
     // Save log periodically during status phase if there are new messages.
-    if (scsiDev.phase == STATUS)
+    // In debug mode, also save every 2 seconds if no SCSI requests come in.
+    // SD card writing takes a while, during which the code can't handle new
+    // SCSI requests, so normally we only want to save during a phase where
+    // the host is waiting for us. But for debugging issues where no requests
+    // come through or a request hangs, it's useful to force saving of log.
+    if (scsiDev.phase == STATUS || (g_log_debug && (uint32_t)(millis() - last_request_time) > 2000))
     {
       save_logfile();
+      last_request_time = millis();
     }
   }