Ensure jshPushIOCharEvent is more stable when the FIFO is full

Author: gfwilliams

ChangeLog

@@ -1,6 +1,7 @@
             nRF5x: Ensure Bluetooth notifications work correctly when two separate connections use the same handle for their characteristics
             nRF5x: Remove handlers from our handlers array when a device is disconnected
             Bangle.js: Fix wrapString when wrapping a non-UTF8 string containing UTF8 characters (fix #2633) 
+            Ensure jshPushIOCharEvent is more stable when the FIFO is full
 
      2v26 : nRF5x: ensure TIMER1_IRQHandler doesn't always wake idle loop up (fix #1900)
             Puck.js: On v2.1 ensure Puck.mag behaves like other variants - just returning the last reading (avoids glitches when used with Puck.magOn)

src/jsdevices.c

@@ -449,8 +449,7 @@ bool CALLED_FROM_INTERRUPT jshPushEvent(IOEventFlags evt, uint8_t *data, unsigne
    * USB and USART data to be coming in at the same time, and it can trip
    * things up if one IRQ interrupts another. */
   jshInterruptOff();
-  int available = IOBUFFERMASK+1-jshGetEventsUsed();
-  if (available < (int)length+2) {
+  if (jshGetIOCharEventsFree() < (int)length+2) {
     jshInterruptOn();
     jshIOEventOverflowed();
     return false; // queue full - dump this event!
@@ -491,7 +490,8 @@ void jshPushIOCharEvents(IOEventFlags channel, char *data, unsigned int count) {
   if (ioLastHead != ioHead &&  // we have a 'last head'
      ioLastHead != ioTail && // it's not something that'll be processed immediately (we're in IRQ so main loop might be in the process right now)
      ioBuffer[(ioLastHead+1)&IOBUFFERMASK] == channel && // same channel
-     ioBuffer[ioLastHead]+count < IOEVENT_MAX_LEN // we have space in this event!
+     ioBuffer[ioLastHead]+count < IOEVENT_MAX_LEN && // we have space in this event!
+     jshGetIOCharEventsFree()>0 // we actually have space in our queue!
      ) {
     // increase event count
     ioBuffer[ioLastHead] += (uint8_t)count;