ESP32 has GPIOs 34-39 that are input only, without internal pull-up. Make them available. (plerup#192)

Author: dok-net

src/SoftwareSerial.cpp

@@ -51,7 +51,7 @@ bool SoftwareSerial::isValidGPIOpin(int8_t pin) {
     return (pin >= 0 && pin <= 16) && !isFlashInterfacePin(pin);
 #elif defined(ESP32)
     return (pin >= 0 && pin <= 5) || (pin >= 12 && pin <= 19) ||
-        (pin >= 21 && pin <= 23) || (pin >= 25 && pin <= 27) || (pin >= 32 && pin < 39);
+        (pin >= 21 && pin <= 23) || (pin >= 25 && pin <= 27) || (pin >= 32 && pin <= 39);
 #else
     return true;
 #endif
@@ -61,12 +61,26 @@ bool SoftwareSerial::isValidRxGPIOpin(int8_t pin) {
     return isValidGPIOpin(pin)
 #if defined(ESP8266)
         && (pin != 16)
-#elif defined(ESP32)
+#endif
+        ;
+}
+
+bool SoftwareSerial::isValidTxGPIOpin(int8_t pin) {
+    return isValidGPIOpin(pin)
+#if defined(ESP32)
         && (pin < 34)
 #endif
         ;
 }
 
+bool SoftwareSerial::hasRxGPIOPullUp(int8_t pin) {
+#if defined(ESP32)
+    return !(pin >= 34 && pin <= 39);
+#else
+    return true;
+#endif
+}
+
 void SoftwareSerial::begin(uint32_t baud, SoftwareSerialConfig config,
     int8_t rxPin, int8_t txPin,
     bool invert, int bufCapacity, int isrBufCapacity) {
@@ -91,10 +105,10 @@ void SoftwareSerial::begin(uint32_t baud, SoftwareSerialConfig config,
             isrBufCapacity : m_buffer->capacity() * (2 + m_dataBits + static_cast<bool>(m_parityMode))));
         if (m_buffer && (!m_parityMode || m_parityBuffer) && m_isrBuffer) {
             m_rxValid = true;
-            pinMode(m_rxPin, INPUT_PULLUP);
+            pinMode(m_rxPin, hasRxGPIOPullUp(m_rxPin) ? INPUT_PULLUP : INPUT);
         }
     }
-    if (isValidGPIOpin(m_txPin)) {
+    if (isValidTxGPIOpin(m_txPin)) {
         m_txValid = true;
         if (!m_oneWire) {
             pinMode(m_txPin, OUTPUT);
@@ -122,7 +136,7 @@ uint32_t SoftwareSerial::baudRate() {
 }
 
 void SoftwareSerial::setTransmitEnablePin(int8_t txEnablePin) {
-    if (isValidGPIOpin(txEnablePin)) {
+    if (isValidTxGPIOpin(txEnablePin)) {
         m_txEnableValid = true;
         m_txEnablePin = txEnablePin;
         pinMode(m_txEnablePin, OUTPUT);
@@ -145,7 +159,7 @@ void SoftwareSerial::enableTx(bool on) {
             digitalWrite(m_txPin, !m_invert);
         }
         else {
-            pinMode(m_rxPin, INPUT_PULLUP);
+            pinMode(m_rxPin, hasRxGPIOPullUp(m_rxPin) ? INPUT_PULLUP : INPUT);
             enableRx(true);
         }
     }

src/SoftwareSerial.h

@@ -215,6 +215,9 @@ class SoftwareSerial : public Stream {
         uint32_t dutyCycle, uint32_t offCycle, bool withStopBit);
     bool isValidGPIOpin(int8_t pin);
     bool isValidRxGPIOpin(int8_t pin);
+    bool isValidTxGPIOpin(int8_t pin);
+    // result is only defined for a valid Rx GPIO pin
+    bool hasRxGPIOPullUp(int8_t pin);
     /* check m_rxValid that calling is safe */
     void rxBits();
     void rxBits(const uint32_t& isrCycle);