add I2S core

cores/esp8266/i2s.h

@@ -0,0 +1,53 @@
+/* 
+  i2s.h - Software I2C library for esp8266
+
+  Copyright (c) 2015 Hristo Gochkov. All rights reserved.
+  This file is part of the esp8266 core for Arduino environment.
+ 
+  This library is free software; you can redistribute it and/or
+  modify it under the terms of the GNU Lesser General Public
+  License as published by the Free Software Foundation; either
+  version 2.1 of the License, or (at your option) any later version.
+
+  This library is distributed in the hope that it will be useful,
+  but WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public
+  License along with this library; if not, write to the Free Software
+  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
+*/
+#ifndef I2S_h
+#define I2S_h
+
+/*
+How does this work? Basically, to get sound, you need to:
+- Connect an I2S codec to the I2S pins on the ESP.
+- Start up a thread that's going to do the sound output
+- Call i2s_begin()
+- Call i2s_set_rate() with the sample rate you want.
+- Generate sound and call i2s_write_sample() with 32-bit samples.
+The 32bit samples basically are 2 16-bit signed values (the analog values for
+the left and right channel) concatenated as (Rout<<16)+Lout
+
+i2s_write_sample will block when you're sending data too quickly, so you can just
+generate and push data as fast as you can and I2sPushSample will regulate the
+speed.
+*/
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+void i2s_begin();
+void i2s_end();
+void i2s_set_rate(uint32_t rate);
+bool i2s_write_sample(uint32_t sample);
+bool i2s_write_lr(int16_t left, int16_t right);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif