diff --git a/sigma_delta.h b/sigma_delta.h
deleted file mode 100644
index 6ed66191d5..0000000000
--- a/sigma_delta.h
+++ /dev/null
@@ -1,72 +0,0 @@
-/* 
- sigma_delta.h - esp8266 sigma-delta source
-
- Copyright (c) 2014 Ivan Grokhotkov. 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
- */
- 
- /*
-/******************************************************************************
- * Info Sigma delta module
-
-This module controls the esp8266 internal sigma delta source
-Each pin can be connected to the sigma delta source
-The target duty and frequency can be modified via the register GPIO_SIGMA_DELTA
-
-THE TARGET FREQUENCY IS DEFINED AS:
-
-FREQ = 80,000,000/prescaler * target /256  HZ,     0<target<128
-FREQ = 80,000,000/prescaler * (256-target) /256  HZ,     128<target<256
-target: duty ,0-255
-prescaler: clk_div,0-255
-so the target and prescale will both affect the freq.
-
-Usage :
-1. sigma_delta_enable() : activate the sigma delta source with default prescalar (0) & target (0)
-2. sigma_delta_attachPin(pin), any pin 0..15, TBC if gpio16 supports sigma-delta source
-     This will set the pin to NORMAL output mode (pinMode(pin,OUTPUT))
-3. sigma_delta_setPrescaler(uint8_t) : reduce the output frequencies
-4. sigma_delta_setTarget(uint8_t) : set the output signal duty cycle, duty cycle = target/256
-
-5. sigma_delta_detachPin(pin), this will revert the pin to NORMAL output mode & GPIO source. 
-The sigma delta source remains on until :
-6. sigma_delta_disable()
-
-*******************************************************************************/
-
-#ifndef SIGMA_DELTA_H
-#define SIGMA_DELTA_H
-
-#ifdef __cplusplus
-extern "C" {
-#endif
-
-void sigma_delta_enable(void);
-void sigma_delta_disable(void);
-void sigma_delta_attachPin(uint8_t pin);
-void sigma_delta_detachPin(uint8_t pin);
-bool sigma_delta_isPinAttached(uint8_t pin);
-uint8_t sigma_delta_getTarget(void);
-void sigma_delta_setTarget(uint8_t target);
-uint8_t sigma_delta_getPrescaler(void);
-void sigma_delta_setPrescaler(uint8_t prescaler);
-
-#ifdef __cplusplus
-}
-#endif
-
-#endif//SIGMA_DELTA_H