Ну у меня все по максимуму Nano2.0, атавизм от использования Nano1.2. Хотя и скорость UART поднята до 250000. Так же включен контроль потока. Но для этого нужно, чтобы и экран этот контроль понимал.
//
@section serial
// The ASCII buffer for serial input
#define MAX_CMD_SIZE 96
#define BUFSIZE 32
// 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.
// For debug-echo: 128 bytes for the optimal speed.
// Other output doesn't need to be that speedy.
// :[0, 2, 4, 8, 16, 32, 64, 128, 256]
#define TX_BUFFER_SIZE 256
// 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 2048
#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