In rxBits(), check for no new intermediate ISR data, inserting extraneous stop bits breaks rx.

Fixes plerup#210.

Author: dok-net

library.json

@@ -1,6 +1,6 @@
 {
     "name": "EspSoftwareSerial",
-    "version": "6.12.5",
+    "version": "6.12.6",
     "description": "Implementation of the Arduino software serial for ESP8266/ESP32.",
     "keywords": [
         "serial", "io", "softwareserial"

library.properties

@@ -1,5 +1,5 @@
 name=EspSoftwareSerial
-version=6.12.5
+version=6.12.6
 author=Dirk Kaar, Peter Lerup
 maintainer=Dirk Kaar <dok@dok-net.net>
 sentence=Implementation of the Arduino software serial for ESP8266/ESP32.

src/SoftwareSerial.cpp

@@ -427,11 +427,13 @@ void SoftwareSerial::rxBits() {
 
     m_isrBuffer->for_each(m_isrBufferForEachDel);
 
-    // stop bit can go undetected if leading data bits are at same level
-    // and there was also no next start bit yet, so one byte may be pending.
+    // A stop bit can go undetected if leading data bits are at same level
+    // and there was also no next start bit yet, so one word may be pending.
+    // Check that there was no new ISR data received in the meantime, inserting an
+    // extraneous stop level bit out of sequence breaks rx.
     if (m_rxCurBit > -1 && m_rxCurBit < m_pduBits - m_stopBits) {
         const uint32_t detectionCycles = (m_pduBits - m_stopBits - m_rxCurBit) * m_bitCycles;
-        if (ESP.getCycleCount() - m_isrLastCycle > detectionCycles) {
+        if (!m_isrBuffer->available() && ESP.getCycleCount() - m_isrLastCycle > detectionCycles) {
             // Produce faux stop bit level, prevents start bit maldetection
             // cycle's LSB is repurposed for the level bit
             rxBits(((m_isrLastCycle + detectionCycles) | 1) ^ m_invert);