Add simple I2S input example code

Author: earlephilhower

cores/esp8266/core_esp8266_i2s.c

@@ -45,16 +45,16 @@ extern void ets_wdt_disable(void);
 // placed onto the list when they're filled by DMA
 
 typedef struct slc_queue_item {
-  uint32_t blocksize : 12;
-  uint32_t datalen   : 12;
-  uint32_t unused    :  5;
-  uint32_t sub_sof   :  1;
-  volatile uint32_t eof       :  1;
-  volatile uint32_t owner     :  1;
-  uint32_t *buf_ptr;
-  uint32_t *next_link_ptr;
+  uint32_t                blocksize : 12;
+  uint32_t                datalen   : 12;
+  uint32_t                unused    :  5;
+  uint32_t                sub_sof   :  1;
+  uint32_t                eof       :  1;
+  volatile uint32_t       owner     :  1; // DMA can change this value
+  uint32_t *              buf_ptr;
+  struct slc_queue_item * next_link_ptr;
   // This is my own way of tracking item ID
-  volatile uint32_t myid;
+  volatile uint32_t       myid;
 } slc_queue_item_t;
 
 typedef struct i2s_state {
@@ -210,7 +210,7 @@ static void ICACHE_FLASH_ATTR _alloc_channel(i2s_state_t *ch) {
     ch->slc_items[x].datalen = SLC_BUF_LEN * 4;
     ch->slc_items[x].blocksize = SLC_BUF_LEN * 4;
     ch->slc_items[x].buf_ptr = (uint32_t*)&ch->slc_buf_pntr[x][0];
-    ch->slc_items[x].next_link_ptr = (uint32_t*)((x<(SLC_BUF_CNT-1))?(&ch->slc_items[x+1]):(&ch->slc_items[0]));
+    ch->slc_items[x].next_link_ptr = (x<(SLC_BUF_CNT-1))?(&ch->slc_items[x+1]):(&ch->slc_items[0]);
     ch->slc_items[x].myid = 0;
   }
 }

libraries/esp8266/examples/I2SInput/I2SInput.ino

@@ -0,0 +1,48 @@
+/*
+   I2S stereo microphone (input) example 
+   Run using the Arduion Serial Plotter to see waveform.
+   Released to the Public Domain by Earle F. Philhower, III
+*/
+
+#include <ESP8266WiFi.h>
+#include <i2s.h>
+
+void dump()
+{
+  Serial.printf("I2SC:    %08x\n", I2SC);
+  Serial.printf("I2SFC:   %08x\n", I2SFC);
+  Serial.printf("I2SCC:   %08x\n", I2SCC);
+  Serial.printf("I2SRXEN: %08x\n", I2SRXEN);
+  Serial.printf("SLCC0:   %08x\n", SLCC0);
+  Serial.printf("SLCRXDC: %08x\n", SLCRXDC);
+  Serial.printf("SLCTXL:  %08x\n", SLCTXL);
+  Serial.printf("SLCIE:   %08x\n", SLCIE);
+}
+
+void setup() {
+  Serial.begin(115200);
+  WiFi.forceSleepBegin();
+  delay(500);
+
+  i2s_rxtx_begin(true, false); // Enable I2S RX
+  i2s_set_rate(11025);
+  dump();
+
+  delay(1000);
+  
+  while (1) {
+    uint32_t l, r;
+    i2s_read_sample(&l, &r, true);
+    int16_t lh = l>>16;
+    int16_t rh = r>>16;
+    char withScale[256];
+    sprintf(withScale, "%d %d", lh, rh);
+    Serial.println(withScale);
+    yield();
+  }
+}
+
+void loop() {
+}
+
+