From f237657e5ebc592c2a8f37546c19a421ee5f37f8 Mon Sep 17 00:00:00 2001
From: sommersoft <sommersoft@gmail.com>
Date: Fri, 23 Mar 2018 18:41:27 +0000
Subject: [PATCH] extended buffer check to usb_cdc_background

---
 ports/atmel-samd/usb.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/ports/atmel-samd/usb.c b/ports/atmel-samd/usb.c
index c95ec06b78..6148c56ae6 100644
--- a/ports/atmel-samd/usb.c
+++ b/ports/atmel-samd/usb.c
@@ -331,6 +331,9 @@ bool usb_connected(void) {
 void usb_cdc_background() {
     //
     if (mp_interrupt_char != -1 && cdc_enabled() && !pending_read) {
-        start_read();
+        // Make sure we have space in the buffer
+        if (usb_rx_count < 64) {
+            start_read();
+        }        
     }
 }