fix for USB serial hangup after suspend/resume

pico_tnc/ax25.c

@@ -31,12 +31,13 @@ SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 #include <stdio.h>
 #include "pico/stdlib.h"
 
-#ifdef RASPBERRYPI_PICO
+#include "ax25.h"
+
+//#ifdef RASPBERRYPI_PICO
+#ifdef PICO_DEFAULT_UART
 
 #include "hardware/dma.h"
 
-#include "ax25.h"
-
 #define OUT_INV (1 << 11)
 #define OUT_REV (1 << 10)
 
@@ -78,11 +79,12 @@ int ax25_fcs(uint32_t crc, const uint8_t *data, int size)
 
 #else
 
+#warning using C standard routine
+
 #define CRC16_POLY 0x10811 /* G(x) = 1 + x^5 + x^12 + x^16 */
 
-int ax25_fcs(int crc, const uint8_t packet[], int length)
+int ax25_fcs(uint32_t crc, const uint8_t packet[], int length)
 {
-    uint32_t crc;
     int i, j;
 
     if (length <= 0) return -1; // packet too short

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) {