ESP32: Per-pin PWM/LEDC frequency and resolution

CHANGELOG.md

@@ -97,6 +97,10 @@
   - Starts with mode as `:output` instead of `:output_pwm`, conserving PWM channels.
   - Mode doesn't change until first call to `#pwm_write`.
   - Calling only `#digital_write` explicitly will keep it in "digital mode".
+  - Set resolution and frequency per `PWMOutput` instance (pin), instead of per `Board`:
+    - `#initialize` hash now accepts `frequency:` and `resolution:` keys.
+    - Or call `#pwm_enable` explicitly with `frequency:` and `resolution:` kwargs.
+    - Only on ESP32 for now. Defaults to 1 kHz and 8-bit when not given.
 
 - `SPI::Peripheral`:
   - Split into `SPI:Peripheral::SinglePin` and `Spi::Peripheral::MultiPin` to allow modeling more complex peripherals.
@@ -124,6 +128,8 @@
 
 ### Board Interface Changes
 
+- `Board#set_pin_mode` now takes a third argument, an `options={}` hash. Only used keys are `resolution:` and `frequency:` for setting PWM resolution. Only works on ESP32 boards so far.
+
 - Added `Board#set_pin_debounce`
   - Implemented for Linux GPIO alerts in `Denko::PiBoard` (denko-piboard gem).
   - Sets a time (in microseconds) that level changes on a pin must be stable for, before an update happens.

examples/pulse_io/pwm_output.rb

@@ -0,0 +1,27 @@
+#
+# Example configuring PWM frequency and resolution. Only on ESP32 for now.
+# Capture output with logic analyzer or oscilloscope to verify accuracy.
+#
+require 'bundler/setup'
+require 'denko'
+
+board = Denko::Board.new(Denko::Connection::Serial.new)
+pwm = Denko::PulseIO::PWMOutput.new(board: board, pin: 2)
+
+# Resolution test: ~1% duty at 1 kHz / 10-bit.
+# On and off approx. 10us and 990us respectively.
+pwm.pwm_enable(frequency: 1_000, resolution: 10)
+pwm.write 10 # of 1023
+sleep 0.5
+pwm.digital_write 0
+
+sleep 0.5
+
+# Frequency test: ~50% duty at 10 kHz / 8-bit.
+# On and off both approx. 50us.
+pwm.pwm_enable(frequency: 10_000, resolution: 8)
+pwm.write 127 # of 255
+sleep 0.5
+pwm.digital_write 0
+
+board.finish_write

src/lib/Denko.h

@@ -27,10 +27,10 @@ class Denko {
     void dacWrite    (byte p, int v,  boolean echo=true);  //cmd = 4
     int  aRead       (byte p);                             //cmd = 5
     void setListener (byte p, boolean enabled, byte analog, byte exponent, boolean local=true); //cmd = 6
-    
+
     // Read value of micros() every loop.
     unsigned long currentTime;
-    
+
     // Counts 1ms ticks based on currentTime. Rolls over every 256ms.
     byte tickCount;
 
@@ -46,7 +46,7 @@ class Denko {
     void findLastActiveListener();
 
     #ifdef ESP32
-      // Use 8 bits for PWM width to match everything else.
+      // 8-bit global PWM resolution by default, to match other boards. Reconfigurable.
       uint8_t esp32AnalogWRes = 8;
       void ledcDetachAll();
     #endif
@@ -119,7 +119,7 @@ class Denko {
     void showLEDArray       (); //cmd = 19
 
     // Bit Bang SPI
-    void spiBBtransfer         (uint8_t clock, uint8_t input, uint8_t output, uint8_t select, uint8_t settings, 
+    void spiBBtransfer         (uint8_t clock, uint8_t input, uint8_t output, uint8_t select, uint8_t settings,
                                 uint8_t rLength, uint8_t wLength, byte *data);                                                          //cmd = 21
     byte spiBBtransferByte     (uint8_t clock, uint8_t input, uint8_t output, uint8_t select,
                                 uint8_t mode, uint8_t bitOrder, byte data);
@@ -132,7 +132,7 @@ class Denko {
     void spiTransfer           (uint32_t clockRate, uint8_t select, uint8_t settings, uint8_t rLength, uint8_t wLength, byte *data);    //cmd = 26
     void spiAddListener        ();                                                                                                      //cmd = 27
     void spiReadListener       (uint8_t i);
- 
+
     // SPI Listeners (both hardware and bit bang)
     void spiRemoveListener     ();                                                                                                      //cmd = 28
     void spiUpdateListeners    ();
@@ -221,7 +221,7 @@ class Denko {
 
     //
     // Shared SPI listeners that can be used by either hardware or bit bang SPI.
-    // 
+    //
     #if defined(DENKO_SPI) || defined(DENKO_SPI_BB)
       // How many SPI lsiteners.
       #define SPI_LISTENER_COUNT 4
@@ -244,7 +244,7 @@ class Denko {
       uint8_t i2c_bb_quarter_period = 1;
 
       // Internal stuff
-      void    i2c_bb_delay_quarter_period(); 
+      void    i2c_bb_delay_quarter_period();
       void    i2c_bb_delay_half_period();
       void    i2c_bb_sda_high   ();
       void    i2c_bb_sda_low    ();

src/lib/DenkoCoreIO.cpp

@@ -7,7 +7,7 @@ void Denko::setMode(byte p, byte m) {
   // Use the lowest 4 bits of m to set different input/output modes.
   // Also enables/disables peripherals for certain targets.
   //
-  // OUTPUT MODES:  
+  // OUTPUT MODES:
   // 0000 = Digital Output
   // 0010 = PWM Ouptut
   // 0100 = DAC Output
@@ -21,38 +21,49 @@ void Denko::setMode(byte p, byte m) {
   m = m & 0b00001111;
 
   #if defined(ESP32)
-    // Free the LEDC channel if leaving PWM mode.
-    if (m != 0b0010) ledcDetach(p);
-
     // Disable attached DAC if leaving DAC mode.
     #if defined(SOC_DAC_SUPPORTED)
-      if (m != 0b0100) dacDisable(p);
+        if (m != 0b0100) dacDisable(p);
     #endif
+
+    // Attach or detach LEDC channel whether entering or leaving PWM mode.
+    if (m == 0b0010) {
+      // auxMsg[0..3] is frequency, [4..7] is resolution.
+      uint32_t freq = *reinterpret_cast<uint32_t *>(auxMsg);
+      uint8_t  res  = *reinterpret_cast<uint8_t *>(auxMsg + 4);
+      // Fallback to defaults.
+      if (freq == 0) freq = 1000;
+      if (res  == 0) res  = esp32AnalogWRes;
+      ledcAttach(p, freq, res);
+      return;
+    } else {
+      ledcDetach(p);
+    }
   #endif
-      
+
   // On the SAMD21 and RA4M1, mode needs to be INPUT when using the DAC.
   #if defined(__SAMD21G18A__) || defined(_RENESAS_RA_)
     if (m == 0b0100){
       pinMode(p, INPUT);
       return;
     }
   #endif
-  
+
   // Handle INPUT_* states on boards implementing them.
   #ifdef INPUT_PULLDOWN
   if (m == 0b0011) {
     pinMode(p, INPUT_PULLDOWN);
     return;
   }
   #endif
-  
+
   #ifdef INPUT_PULLUP
   if (m == 0b0101) {
     pinMode(p, INPUT_PULLUP);
     return;
   }
   #endif
-  
+
   // Handle OUTPUT_* states on boards implementing them.
   #ifdef OUTPUT_OPEN_DRAIN
   if (m == 0b0110) {
@@ -100,7 +111,7 @@ void Denko::dWrite(byte p, byte v, boolean echo) {
     #endif
     ledcDetach(p);
   #endif
-    
+
   if (v == 0) {
     digitalWrite(p, LOW);
   }
@@ -122,8 +133,6 @@ byte Denko::dRead(byte p) {
 // Write an analog output pin. 0 for LOW, up to 255 for HIGH @ 8-bit resolution.
 void Denko::pwmWrite(byte p, int v, boolean echo) {
   #ifdef ESP32
-    // Try to reattach LEDC each time. Should be cached, and dWrite might detatch it.
-    ledcAttach(p, 1000, esp32AnalogWRes);
     ledcWrite(p, v);
   #else
     analogWrite(p,v);
@@ -145,7 +154,7 @@ void Denko::dacWrite(byte p, int v, boolean echo) {
   #if defined(ESP32) && defined(SOC_DAC_SUPPORTED)
     ::dacWrite(p, v);
   #endif
-    
+
   #if defined(__SAM3X8E__) || defined(__SAMD21G18A__) || defined(_RENESAS_RA_)
     analogWrite(p, v);
   #endif