working code for sigma delta generator

cores/esp8266/core_esp8266_sigma_delta.c

@@ -0,0 +1,154 @@
+/*
+/******************************************************************************
+ * 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()
+
+*******************************************************************************/
+
+#include "Arduino.h" // using pinMode
+
+// definitions in esp8266_peri.h style
+#define GPSD  ESP8266_REG(0x368) // GPIO_SIGMA_DELTA register @ 0x600000368
+#define GPSDT 0  // target, 8 bits
+#define GPSDP 8  // prescaler, 8 bits
+#define GPSDE 16 // enable
+
+/******************************************************************************
+ * FunctionName : sigma_delta_start
+ * Description  : enable the internal sigma delta source
+ * Parameters   : none
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_enable()
+{
+  GPSD = (0 << GPSDT) | (0 << GPSDP) | (1 << GPSDE); //SIGMA_DELTA_TARGET(0) | SIGMA_DELTA_PRESCALER(0) | SIGMA_DELTA_ENABLE(ENABLED)
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_disable
+ * Description  : stop the internal sigma delta source
+ * Parameters   : none
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_disable()
+{
+  GPSD = (0 << GPSDT) | (0 << GPSDP) | (0 << GPSDE); //SIGMA_DELTA_TARGET(0) | SIGMA_DELTA_PRESCALER(0) | SIGMA_DELTA_ENABLE(DISABLED)
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_attachPin
+ * Description  : connects the sigma delta source to a physical output pin
+ * Parameters   : pin (0..15)
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_attachPin(uint8_t pin)
+{
+  // make the chosen pin an output pin
+  pinMode (pin, OUTPUT);
+  if (pin < 16) {
+    // set its source to the sigma delta source
+    GPC(pin) |= (1 << GPCS); //SOURCE 0:GPIO_DATA,1:SigmaDelta
+  }
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_detachPin
+ * Description  : disconnects the sigma delta source from a physical output pin
+ * Parameters   : pin (0..16)
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_detachPin(uint8_t pin)
+{
+  if (pin < 16) {
+    // set its source to the sigma delta source
+    GPC(pin) &=  ~(1 << GPCS); //SOURCE 0:GPIO_DATA,1:SigmaDelta
+  }
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_isPinAttached
+ * Description  : query if pin is attached
+ * Parameters   : pin (0..16)
+ * Returns      : bool
+*******************************************************************************/
+bool ICACHE_FLASH_ATTR sigma_delta_isPinAttached(uint8_t pin)
+{
+  if (pin < 16) {
+    // set its source to the sigma delta source
+     return (GPC(pin) & (1 << GPCS)); //SOURCE 0:GPIO_DATA,1:SigmaDelta
+  }
+  else
+    return false;
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_getTarget
+ * Description  : get the target value from the GPIO_SIGMA_DELTA register
+ * Parameters   : none
+ * Returns      : uint8_t target value 0..255
+*******************************************************************************/
+uint8_t ICACHE_FLASH_ATTR sigma_delta_getTarget(void)
+{
+  return (uint8_t)((GPSD >> GPSDT) & 0xFF);
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_setTarget
+ * Description  : set the target (duty cycle) for the sigma-delta source
+ * Parameters   : uint8 target, 0-255, duty cycle = target/256
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_setTarget(uint8_t target)
+{
+  uint32_t reg = GPSD;
+
+  reg = (reg & ~(0xFF << GPSDT)) | ((target & 0xFF) << GPSDT);
+  GPSD = reg;
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_getPrescaler
+ * Description  : get the prescaler value from the GPIO_SIGMA_DELTA register
+ * Parameters   : none
+ * Returns      : uint8 prescaler, CLK_DIV , 0-255
+*******************************************************************************/
+uint8_t ICACHE_FLASH_ATTR sigma_delta_getPrescaler(uint8_t prescaler)
+{
+  return (uint8_t)((GPSD >> GPSDP) & 0xFF);
+}
+
+/******************************************************************************
+ * FunctionName : sigma_delta_setPrescaler
+ * Description  : set the clock divider for the sigma-delta source
+ * Parameters   : uint8 prescaler, 0-255, divides the 80MHz base clock by this amount
+ * Returns      : none
+*******************************************************************************/
+void ICACHE_FLASH_ATTR sigma_delta_setPrescaler(uint8_t prescaler)
+{
+  uint32_t reg = GPSD;
+
+  reg = (reg & ~(0xFF << GPSDP)) | ((prescaler & 0xFF) << GPSDP);
+  GPSD = reg;
+}

cores/esp8266/sigma_delta.h

@@ -18,15 +18,112 @@
  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()
+
+copy this code as example :
+
+#include "sigma_delta.h"
+
+void setup() {
+
+  Serial.begin(115200);
+  pinMode(BUILTIN_LED,OUTPUT); // blinkie & sigma-delta mix
+  
+  uint32 pin = 4; //D2
+  sigma_delta_enable();
+  //sigma_delta_disable();
+  sigma_delta_attachPin(BUILTIN_LED);
+  sigma_delta_attachPin(4); // D2
+  
+  sigma_delta_setPrescaler(255);
+
+  Serial.println();
+  Serial.println("Start Sigma Delta Example\n");
+  Serial.println("Attached gpio4 to the sigma delta source\n");
+  Serial.printf("Current target = %i, prescaler = %i\n",sigma_delta_getTarget(),sigma_delta_getPrescaler());
+}
+
+void loop() {
+ 
+  uint8_t target, iRepeat;
+  
+  Serial.println("Attaching the built in led to the sigma delta source now\n");
+  Serial.printf("Current target = %i, prescaler = %i\n",sigma_delta_getTarget(),sigma_delta_getPrescaler());
+  sigma_delta_attachPin(BUILTIN_LED);
+  
+  Serial.println("dimming builtin led...\n");
+  for (iRepeat=0;iRepeat<10;iRepeat++)
+  {
+    for (target=0; target<255;target=target+5)
+    {
+      sigma_delta_setTarget(target);
+      delay(10);
+    }
+    
+    for (target=255; target>0;target=target-5)
+    {
+      sigma_delta_setTarget(target);
+      delay(10);
+    }
+    
+  }
+  Serial.println("detaching builtin led & playing a blinkie\n");
+  sigma_delta_detachPin(BUILTIN_LED);
+  for (iRepeat=0;iRepeat<20;iRepeat++)
+  {
+    digitalWrite(BUILTIN_LED,!digitalRead(BUILTIN_LED));
+    delay(500);
+  }
+    
+}
+
+*******************************************************************************/
 
 #ifndef SIGMA_DELTA_H
 #define SIGMA_DELTA_H
 
-#include <stdint.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);
 
-void sigma_delta_close(uint32_t gpio);
-void set_sigma_target(uint8_t target);
-void set_sigma_prescale(uint8_t prescale);
-void set_sigma_duty_312KHz(uint8_t duty);
+#ifdef __cplusplus
+}
+#endif
 
 #endif//SIGMA_DELTA_H

libraries/esp8266/examples/SigmaDeltaDemo/SigmaDeltaDemo.ino

@@ -0,0 +1,84 @@
+/*
+  Sigma Delta Generator example
+  
+  This example demonstrates the use of the ESP8266 internal hardware sigma delta source.
+  Each GPIO pin or multiple pins can be connected to the one sigma delta source.
+  THE sigma delta output frequency is defined by the ESP8266 hardware as:
+
+  FREQ = 80,000,000/prescaler * target /256  HZ,          0<target<128
+  FREQ = 80,000,000/prescaler * (256-target) /256  HZ,    128<target<256
+  with :
+  target: 0-255, defines the 8-bit duty cycle of the output signal, , duty cycle = target/256
+  prescaler: 0-255, reduce the output frequencies
+  
+  so both the target and prescaler will affect the freq.
+  
+  Differences with Arduino library analogWrite :
+  - the arduino analogWrite pwm uses a hardware timer and ISR to generate the pwm signal. The sigma delta pwm doesn't need a hardware timer. 
+    The FRC1 timer can then be used for other purposes.
+  - the arduino analogWrite pwm produces a more or less fixed frequency around 900Hz. The sigma delta source produces a variable output frequency, 
+    that depends on the duty cycle. Example, with prescaler = 10, the output frequency varies between 31,kHz and 4MHz
+  - the sigma delta source produces much higher frequencies. This allows the output to be easily smoothed by a RC-filter and realise a decent 8-bit DAC
+  - the arduino analogWrite pwm has a higher resolution, default 12-bit, and up to 16-bit resolution. The sigma delta source has only 8-bit resolution
+    
+  The example doesn't require additional hardware.
+  
+  With an RC-filter (for example R=17k & C=100nF), a 'DC' output signal can be obtained with voltage between 0 and 3.3V
+  For higher value capacitors, it might be necessary to add a high-speed buffer between the esp8266 output and RC-filter to limit the current ac load on the 
+  pin output driver.
+
+*/
+#include "sigma_delta.h"
+
+void setup() {
+
+  Serial.begin(115200);
+  pinMode(BUILTIN_LED,OUTPUT); // blinkie & sigma-delta mix
+
+  uint32 pin = 4; //D2
+  sigma_delta_enable();
+  //sigma_delta_disable();
+  sigma_delta_attachPin(BUILTIN_LED);
+  sigma_delta_attachPin(4); // D2
+
+  sigma_delta_setPrescaler(255);
+
+  Serial.println();
+  Serial.println("Start Sigma Delta Example\n");
+  Serial.println("Attached gpio4 to the sigma delta source\n");
+  Serial.printf("Current target = %i, prescaler = %i\n",sigma_delta_getTarget(),sigma_delta_getPrescaler());
+}
+
+void loop() {
+
+  uint8_t target, iRepeat;
+
+  Serial.println("Attaching the built in led to the sigma delta source now\n");
+  Serial.printf("Current target = %i, prescaler = %i\n",sigma_delta_getTarget(),sigma_delta_getPrescaler());
+  sigma_delta_attachPin(BUILTIN_LED);
+
+  Serial.println("dimming builtin led...\n");
+  for (iRepeat=0;iRepeat<10;iRepeat++)
+  {
+    for (target=0; target<255;target=target+5)
+    {
+      sigma_delta_setTarget(target);
+      delay(10);
+    }
+
+    for (target=255; target>0;target=target-5)
+    {
+      sigma_delta_setTarget(target);
+      delay(10);
+    }
+
+  }
+  Serial.println("detaching builtin led & playing a blinkie\n");
+  sigma_delta_detachPin(BUILTIN_LED);
+  for (iRepeat=0;iRepeat<20;iRepeat++)
+  {
+    digitalWrite(BUILTIN_LED,!digitalRead(BUILTIN_LED));
+    delay(500);
+  }
+
+}