From e6c065588f1a35f94f8bcbdbb8c5bdedc4615265 Mon Sep 17 00:00:00 2001
From: amedes <amedes@dff.mydns.jp>
Date: Mon, 10 Jul 2023 13:36:37 +0900
Subject: [PATCH] fix for USB serial hangup after suspend/resume

---
 pico_tnc/usb_output.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pico_tnc/usb_output.c b/pico_tnc/usb_output.c
index 88383bd..ea5eae8 100644
--- a/pico_tnc/usb_output.c
+++ b/pico_tnc/usb_output.c
@@ -45,6 +45,8 @@ void usb_write(uint8_t const *data, int len)
 {
     int i;
 
+    if (!tud_cdc_connected()) return;
+
     if (!queue_is_empty(&usb_queue)) {
 
         for (i = 0; i < len; i++) {
@@ -73,6 +75,8 @@ void usb_write_char(uint8_t ch)
 {
     int i = 0;
 
+    if (!tud_cdc_connected()) return;
+
     if (!queue_is_empty(&usb_queue)) {
 
         queue_try_add(&usb_queue, &ch);
@@ -93,6 +97,8 @@ void usb_output(void)
 {
     uint8_t data;
 
+    if (!tud_cdc_connected()) return;
+
     if (queue_is_empty(&usb_queue)) return;
 
     while (tud_cdc_write_available() > 0) {