i2s: adds i2s_rxtxdrive_begin(enableRx, enableTx, driveRxClocks, driveTxClocks) (esp8266#7748)

Two parameters are added to allow using only i2s-in/out-data pin.
This is necessary when i2so-bck and i2so-ws are repurposed
especially because they overlap with SPI GPIO.

Author: d-a-v

cores/esp8266/core_esp8266_i2s.cpp

@@ -64,6 +64,7 @@ typedef struct i2s_state {
   // Callback function should be defined as 'void ICACHE_RAM_ATTR function_name()',
   // and be placed in IRAM for faster execution. Avoid long computational tasks in this
   // function, use it to set flags and process later.
+  bool             driveClocks;
 } i2s_state_t;
 
 // RX = I2S receive (i.e. microphone), TX = I2S transmit (i.e. DAC)
@@ -493,6 +494,10 @@ float i2s_get_real_rate(){
 }
 
 bool i2s_rxtx_begin(bool enableRx, bool enableTx) {
+  return i2s_rxtxdrive_begin(enableRx, enableTx, true, true);
+}
+
+bool i2s_rxtxdrive_begin(bool enableRx, bool enableTx, bool driveRxClocks, bool driveTxClocks) {
   if (tx || rx) {
     i2s_end(); // Stop and free any ongoing stuff
   }
@@ -503,22 +508,28 @@ bool i2s_rxtx_begin(bool enableRx, bool enableTx) {
       // Nothing to clean up yet
       return false; // OOM Error!
     }
-    pinMode(I2SO_WS, FUNCTION_1);
+    tx->driveClocks = driveTxClocks;
     pinMode(I2SO_DATA, FUNCTION_1);
-    pinMode(I2SO_BCK, FUNCTION_1);
+    if (driveTxClocks) {
+      pinMode(I2SO_WS, FUNCTION_1);
+      pinMode(I2SO_BCK, FUNCTION_1);
+    }
   }
   if (enableRx) {
     rx = (i2s_state_t*)calloc(1, sizeof(*rx));
     if (!rx) {
       i2s_end(); // Clean up any TX or pin changes
       return false; // OOM error!
     }
-    pinMode(I2SI_WS, OUTPUT);
-    pinMode(I2SI_BCK, OUTPUT);
+    rx->driveClocks = driveRxClocks;
     pinMode(I2SI_DATA, INPUT);
+    if (driveRxClocks) {
+      pinMode(I2SI_WS, OUTPUT);
+      pinMode(I2SI_BCK, OUTPUT);
+      PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTCK_U, FUNC_I2SI_BCK);
+      PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTMS_U, FUNC_I2SI_WS);
+    }
     PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTDI_U, FUNC_I2SI_DATA);
-    PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTCK_U, FUNC_I2SI_BCK);
-    PIN_FUNC_SELECT(PERIPHS_IO_MUX_MTMS_U, FUNC_I2SI_WS);
   }
 
   if (!i2s_slc_begin()) {
@@ -579,15 +590,19 @@ void i2s_end() {
 
   if (tx) {
     pinMode(I2SO_DATA, INPUT);
-    pinMode(I2SO_BCK, INPUT);
-    pinMode(I2SO_WS, INPUT);
+    if (tx->driveClocks) {
+      pinMode(I2SO_BCK, INPUT);
+      pinMode(I2SO_WS, INPUT);
+    }
     free(tx);
     tx = NULL;
   }
   if (rx) {
     pinMode(I2SI_DATA, INPUT);
-    pinMode(I2SI_BCK, INPUT);
-    pinMode(I2SI_WS, INPUT);
+    if (rx->driveClocks) {
+      pinMode(I2SI_BCK, INPUT);
+      pinMode(I2SI_WS, INPUT);
+    }
     free(rx);
     rx = NULL;
   }

cores/esp8266/i2s.h

@@ -21,6 +21,8 @@
 #ifndef I2S_h
 #define I2S_h
 
+#define I2S_HAS_BEGIN_RXTX_DRIVE_CLOCKS 1
+
 /*
 How does this work? Basically, to get sound, you need to:
 - Connect an I2S codec to the I2S pins on the ESP.
@@ -42,6 +44,7 @@ extern "C" {
 
 void i2s_begin(); // Enable TX only, for compatibility
 bool i2s_rxtx_begin(bool enableRx, bool enableTx); // Allow TX and/or RX, returns false on OOM error
+bool i2s_rxtxdrive_begin(bool enableRx, bool enableTx, bool driveRxClocks, bool driveTxClocks);
 void i2s_end();
 void i2s_set_rate(uint32_t rate);//Sample Rate in Hz (ex 44100, 48000)
 void i2s_set_dividers(uint8_t div1, uint8_t div2);//Direct control over output rate