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earlephilhowerearlephilhower
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Add support for hardware Sigma Delta generator
Provides a simple interface to attach/detach pins to the sigma-delta generator, and get/set the 2 parameters prescaler & target. Working example that fades the onboard LED is provided. Code and sample by @stefaandesmet2003.
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‎cores/esp8266/core_esp8266_sigma_delta.c

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/*
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core_esp8266_sigma_delta.c - sigma delta library for esp8266
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Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
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This file is part of the esp8266 core for Arduino environment.
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This library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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This library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "Arduino.h" // using pinMode
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// definitions in esp8266_peri.h style
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#define GPSD ESP8266_REG(0x368) // GPIO_SIGMA_DELTA register @ 0x600000368
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#define GPSDT 0 // target, 8 bits
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#define GPSDP 8 // prescaler, 8 bits
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#define GPSDE 16 // enable
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void sigmaDeltaSetPrescaler(uint8_t prescaler); // avoids compiler warning
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/******************************************************************************
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* FunctionName : sigmaDeltaEnable
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* Description : enable the internal sigma delta source
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* Parameters : none
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaEnable()
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{
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GPSD = (0 << GPSDT) | (0 << GPSDP) | (1 << GPSDE); //SIGMA_DELTA_TARGET(0) | SIGMA_DELTA_PRESCALER(0) | SIGMA_DELTA_ENABLE(ENABLED)
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaDisable
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* Description : stop the internal sigma delta source
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* Parameters : none
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaDisable()
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{
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GPSD = (0 << GPSDT) | (0 << GPSDP) | (0 << GPSDE); //SIGMA_DELTA_TARGET(0) | SIGMA_DELTA_PRESCALER(0) | SIGMA_DELTA_ENABLE(DISABLED)
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaAttachPin
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* Description : connects the sigma delta source to a physical output pin
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* Parameters : pin (0..15), channel = unused, for compatibility with ESP32
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaAttachPin(uint8_t pin, uint8_t channel)
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{
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(void) channel;
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// make the chosen pin an output pin
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pinMode (pin, OUTPUT);
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if (pin < 16) {
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// set its source to the sigma delta source
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GPC(pin) |= (1 << GPCS); //SOURCE 0:GPIO_DATA,1:SigmaDelta
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}
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaDetachPin
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* Description : disconnects the sigma delta source from a physical output pin
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* Parameters : pin (0..16)
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaDetachPin(uint8_t pin)
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{
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if (pin < 16) {
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// set its source to the sigma delta source
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GPC(pin) &= ~(1 << GPCS); //SOURCE 0:GPIO_DATA,1:SigmaDelta
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}
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaIsPinAttached
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* Description : query if pin is attached
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* Parameters : pin (0..16)
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* Returns : bool
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*******************************************************************************/
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bool ICACHE_FLASH_ATTR sigmaDeltaIsPinAttached(uint8_t pin)
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{
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if (pin < 16) {
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// set its source to the sigma delta source
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return (GPC(pin) & (1 << GPCS)); //SOURCE 0:GPIO_DATA,1:SigmaDelta
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}
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else
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return false;
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaSetup
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* Description : start the sigma delta generator with the chosen parameters
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* Parameters : channel = unused (for compatibility with ESP32),
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* freq : 1220-312500 (lowest frequency in the output signal's spectrum)
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* Returns : uint32_t the actual frequency, closest to the input parameter
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*******************************************************************************/
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uint32_t ICACHE_FLASH_ATTR sigmaDeltaSetup(uint8_t channel, uint32_t freq)
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{
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(void) channel;
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uint32_t prescaler = ((uint32_t)10000000/(freq*32)) - 1;
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if(prescaler > 0xFF) {
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prescaler = 0xFF;
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}
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sigmaDeltaEnable();
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sigmaDeltaSetPrescaler ((uint8_t) prescaler);
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return 10000000/((prescaler + 1) * 32);
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaWrite
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* Description : set the duty cycle for the sigma-delta source
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* Parameters : uint8 duty, 0-255, duty cycle = target/256,
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* channel = unused, for compatibility with ESP32
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaWrite(uint8_t channel, uint8_t duty)
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{
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uint32_t reg = GPSD;
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(void) channel;
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reg = (reg & ~(0xFF << GPSDT)) | ((duty & 0xFF) << GPSDT);
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GPSD = reg;
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaRead
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* Description : get the duty cycle for the sigma-delta source
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* Parameters : channel = unused, for compatibility with ESP32
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* Returns : uint8_t duty cycle value 0..255
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*******************************************************************************/
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uint8_t ICACHE_FLASH_ATTR sigmaDeltaRead(uint8_t channel)
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{
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(void) channel;
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return (uint8_t)((GPSD >> GPSDT) & 0xFF);
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaSetPrescaler
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* Description : set the clock divider for the sigma-delta source
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* Parameters : uint8 prescaler, 0-255, divides the 80MHz base clock by this amount
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* Returns : none
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*******************************************************************************/
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void ICACHE_FLASH_ATTR sigmaDeltaSetPrescaler(uint8_t prescaler)
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{
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uint32_t reg = GPSD;
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reg = (reg & ~(0xFF << GPSDP)) | ((prescaler & 0xFF) << GPSDP);
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GPSD = reg;
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}
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/******************************************************************************
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* FunctionName : sigmaDeltaGetPrescaler
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* Description : get the prescaler value from the GPIO_SIGMA_DELTA register
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* Parameters : none
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* Returns : uint8 prescaler, CLK_DIV , 0-255
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*******************************************************************************/
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uint8_t ICACHE_FLASH_ATTR sigmaDeltaGetPrescaler(void)
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{
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return (uint8_t)((GPSD >> GPSDP) & 0xFF);
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}

‎cores/esp8266/sigma_delta.h

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License along with this library; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
2020
*/
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/*******************************************************************************
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* Info Sigma delta module
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This module controls the esp8266 internal sigma delta source
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Each pin can be connected to the sigma delta source
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The target duty and frequency can be modified via the register GPIO_SIGMA_DELTA
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THE TARGET FREQUENCY IS DEFINED AS:
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FREQ = 80,000,000/prescaler * target /256 HZ, 0<target<128
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FREQ = 80,000,000/prescaler * (256-target) /256 HZ, 128<target<256
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target: duty cycle,range 0-255
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prescaler: is a clock divider, range 0-255
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so the target and prescale will both affect the freq.
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CPU_FREQ has no influence on the sigma delta frequency.
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Usage :
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1. sigmaDeltaSetup(0,f) : activate the sigma delta source with frequency f and default duty cycle (0)
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2. sigmaDeltaAttachPin(pin), any pin 0..15, TBC if gpio16 supports sigma-delta source
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This will set the pin to NORMAL output mode (pinMode(pin,OUTPUT))
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3. sigmaDeltaWrite(0,dc) : set the output signal duty cycle, duty cycle = dc/256
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*******************************************************************************/
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#ifndef SIGMA_DELTA_H
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#define SIGMA_DELTA_H
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#include <stdint.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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//channel parameter is unused (only for ESP32 compatibility) freq 1220-312500 duty 0-255
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void sigmaDeltaEnable(void);
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void sigmaDeltaDisable(void);
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uint32_t sigmaDeltaSetup(uint8_t channel, uint32_t freq);
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void sigmaDeltaWrite(uint8_t channel, uint8_t duty);
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uint8_t sigmaDeltaRead(uint8_t channel = 0);
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void sigmaDeltaAttachPin(uint8_t pin, uint8_t channel = 0);
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void sigmaDeltaDetachPin(uint8_t pin);
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bool sigmaDeltaIsPinAttached(uint8_t pin);
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// alternative way to control the sigma delta generator frequency
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uint8_t sigmaDeltaGetPrescaler(void);
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void sigmaDeltaSetPrescaler(uint8_t prescaler);
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void sigma_delta_close(uint32_t gpio);
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void set_sigma_target(uint8_t target);
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void set_sigma_prescale(uint8_t prescale);
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void set_sigma_duty_312KHz(uint8_t duty);
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#ifdef __cplusplus
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}
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#endif
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#endif//SIGMA_DELTA_H

‎libraries/esp8266/examples/SigmaDeltaDemo/SigmaDeltaDemo.ino

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/* Any copyright is dedicated to the Public Domain. */
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#include "sigma_delta.h"
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void setup() {
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Serial.begin(115200);
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pinMode(LED_BUILTIN, OUTPUT); // blinkie & sigma-delta mix
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uint32_t reqFreq = 1000;
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uint32_t realFreq;
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realFreq = sigmaDeltaSetup(0, reqFreq); // chose a low frequency
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Serial.println();
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Serial.println("Start Sigma Delta Example\n");
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Serial.printf("Frequency = %u\n", realFreq);
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}
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void loop() {
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uint8_t duty, iRepeat;
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Serial.println("Attaching the built in led to the sigma delta source now\n");
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Serial.printf("Current duty = %i, prescaler = %i\n", sigmaDeltaRead(), sigmaDeltaGetPrescaler());
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sigmaDeltaAttachPin(LED_BUILTIN);
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Serial.println("Dimming builtin led...\n");
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for (iRepeat = 0; iRepeat < 10; iRepeat++) {
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for (duty = 0; duty < 255; duty = duty + 5) {
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sigmaDeltaWrite(0, duty);
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delay(10);
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}
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for (duty = 255; duty > 0; duty = duty - 5) {
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sigmaDeltaWrite(0, duty);
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delay(10);
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}
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}
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Serial.println("Detaching builtin led & playing a blinkie\n");
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sigmaDeltaDetachPin(LED_BUILTIN);
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for (iRepeat = 0; iRepeat < 20; iRepeat++) {
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digitalWrite(LED_BUILTIN, !digitalRead(LED_BUILTIN));
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delay(500);
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}
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}

‎sigma_delta.h

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/*
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sigma_delta.h - esp8266 sigma-delta source
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Copyright (c) 2014 Ivan Grokhotkov. All rights reserved.
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This file is part of the esp8266 core for Arduino environment.
6+
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This library is free software; you can redistribute it and/or
8+
modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
10+
version 2.1 of the License, or (at your option) any later version.
11+
12+
This library is distributed in the hope that it will be useful,
13+
but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
18+
License along with this library; if not, write to the Free Software
19+
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/*
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/******************************************************************************
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* Info Sigma delta module
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This module controls the esp8266 internal sigma delta source
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Each pin can be connected to the sigma delta source
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The target duty and frequency can be modified via the register GPIO_SIGMA_DELTA
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THE TARGET FREQUENCY IS DEFINED AS:
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FREQ = 80,000,000/prescaler * target /256 HZ, 0<target<128
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FREQ = 80,000,000/prescaler * (256-target) /256 HZ, 128<target<256
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target: duty ,0-255
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prescaler: clk_div,0-255
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so the target and prescale will both affect the freq.
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Usage :
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1. sigma_delta_enable() : activate the sigma delta source with default prescalar (0) & target (0)
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2. sigma_delta_attachPin(pin), any pin 0..15, TBC if gpio16 supports sigma-delta source
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This will set the pin to NORMAL output mode (pinMode(pin,OUTPUT))
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3. sigma_delta_setPrescaler(uint8_t) : reduce the output frequencies
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4. sigma_delta_setTarget(uint8_t) : set the output signal duty cycle, duty cycle = target/256
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5. sigma_delta_detachPin(pin), this will revert the pin to NORMAL output mode & GPIO source.
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The sigma delta source remains on until :
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6. sigma_delta_disable()
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*******************************************************************************/
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#ifndef SIGMA_DELTA_H
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#define SIGMA_DELTA_H
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#ifdef __cplusplus
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extern "C" {
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#endif
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void sigma_delta_enable(void);
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void sigma_delta_disable(void);
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void sigma_delta_attachPin(uint8_t pin);
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void sigma_delta_detachPin(uint8_t pin);
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bool sigma_delta_isPinAttached(uint8_t pin);
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uint8_t sigma_delta_getTarget(void);
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void sigma_delta_setTarget(uint8_t target);
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uint8_t sigma_delta_getPrescaler(void);
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void sigma_delta_setPrescaler(uint8_t prescaler);
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#ifdef __cplusplus
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}
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#endif
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#endif//SIGMA_DELTA_H

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