Add XON/XOFF options to example configs

Marlin/src/config/examples/delta/FLSUN/kossel_mini/Configuration.h

@@ -108,8 +108,9 @@
  *
  * 250000 works in most cases, but you might try a lower speed if
  * you commonly experience drop-outs during host printing.
+ * You may try up to 1000000 to speed up SD file transfer.
  *
- * :[2400, 9600, 19200, 38400, 57600, 115200, 250000]
+ * :[2400, 9600, 19200, 38400, 57600, 115200, 250000, 500000, 1000000]
  */
 #define BAUDRATE 250000
 

Marlin/src/config/examples/delta/FLSUN/kossel_mini/Configuration_adv.h

@@ -753,7 +753,7 @@
 #define MAX_CMD_SIZE 96
 #define BUFSIZE 4
 
-// Transfer Buffer Size
+// Transmission to Host Buffer Size
 // To save 386 bytes of PROGMEM (and TX_BUFFER_SIZE+3 bytes of RAM) set to 0.
 // To buffer a simple "ok" you need 4 bytes.
 // For ADVANCED_OK (M105) you need 32 bytes.
@@ -762,6 +762,28 @@
 // :[0, 2, 4, 8, 16, 32, 64, 128, 256]
 #define TX_BUFFER_SIZE 0
 
+// Host Receive Buffer Size
+// Without XON/XOFF flow control (see SERIAL_XON_XOFF below) 32 bytes should be enough.
+// To use flow control, set this buffer size to at least 1024 bytes.
+// :[0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048]
+//#define RX_BUFFER_SIZE 1024
+
+#if RX_BUFFER_SIZE >= 1024
+  // Enable to have the controller send XON/XOFF control characters to
+  // the host to signal the RX buffer is becoming full.
+  //#define SERIAL_XON_XOFF
+#endif
+
+#if ENABLED(SDSUPPORT)
+  // Enable this option to collect and display the maximum
+  // RX queue usage after transferring a file to SD.
+  //#define SERIAL_STATS_MAX_RX_QUEUED
+
+  // Enable this option to collect and display the number
+  // of dropped bytes after a file transfer to SD.
+  //#define SERIAL_STATS_DROPPED_RX
+#endif
+
 // Enable an emergency-command parser to intercept certain commands as they
 // enter the serial receive buffer, so they cannot be blocked.
 // Currently handles M108, M112, M410