[HAL] Add tones support for the RPi Pico (#1239)

* Add tones support for RPi Pico

* Add dependencies to CMakeLists

* Address review

examples/NonArduino/Pico/CMakeLists.txt

@@ -23,11 +23,11 @@ add_executable(${PROJECT_NAME}
 )
 
 # Pull in common dependencies
-target_link_libraries(${PROJECT_NAME} pico_stdlib hardware_spi hardware_gpio hardware_timer RadioLib)
+target_link_libraries(${PROJECT_NAME} pico_stdlib hardware_spi hardware_gpio hardware_timer pico_multicore hardware_pwm RadioLib)
 
 
 pico_enable_stdio_usb(${PROJECT_NAME} 1)
 pico_enable_stdio_uart(${PROJECT_NAME} 0)
 
 # Create map/bin/hex file etc.
-pico_add_extra_outputs(${PROJECT_NAME})
+pico_add_extra_outputs(${PROJECT_NAME})

examples/NonArduino/Pico/PicoHal.h

@@ -8,6 +8,45 @@
 #include <pico/stdlib.h>
 #include "hardware/spi.h"
 #include "hardware/timer.h"
+#include "hardware/pwm.h"
+#include "hardware/clocks.h"
+#include "pico/multicore.h"
+
+uint32_t toneLoopPin;
+unsigned int toneLoopFrequency;
+unsigned long toneLoopDuration;
+
+// pre-calculated pulse-widths for 1200 and 2200Hz
+// we do this to save calculation time (see https://github.com/khoih-prog/RP2040_PWM/issues/6)
+#define SLEEP_1200 416.666
+#define SLEEP_2200 227.272
+
+// === NOTE ===
+// The tone(...) implementation uses the second core on the RPi Pico. This is to diminish as much 
+// jitter in the output tones as possible.
+
+void toneLoop(){
+  gpio_set_dir(toneLoopPin, GPIO_OUT);
+
+  uint32_t sleep_dur;
+  if (toneLoopFrequency == 1200) {
+    sleep_dur = SLEEP_1200;
+  } else if (toneLoopFrequency == 2200) {
+    sleep_dur = SLEEP_2200;
+  } else {
+    sleep_dur = 500000 / toneLoopFrequency;
+  }
+
+
+  // tone bitbang
+  while(1){
+    gpio_put(toneLoopPin, 1);
+    sleep_us(sleep_dur);
+    gpio_put(toneLoopPin, 0);
+    sleep_us(sleep_dur);
+    tight_loop_contents();
+  }
+}
 
 // create a new Raspberry Pi Pico hardware abstraction 
 // layer using the Pico SDK
@@ -21,8 +60,7 @@ public:
     _spiSpeed(spiSpeed),
     _misoPin(misoPin),
     _mosiPin(mosiPin),
-    _sckPin(sckPin) {
+    _sckPin(sckPin){}
-    }
 
   void init() override {
     stdio_init_all();
@@ -110,6 +148,19 @@ public:
     return (this->micros() - start);
   }
 
+  void tone(uint32_t pin, unsigned int frequency, unsigned long duration = 0) override {
+    // tones on the Pico are generated using bitbanging. This process is offloaded to the Pico's second core
+    multicore_reset_core1();
+    toneLoopPin = pin;
+    toneLoopFrequency = frequency;
+    toneLoopDuration = duration;
+    multicore_launch_core1(toneLoop);
+  }
+
+  void noTone(uint32_t pin) override {
+    multicore_reset_core1();
+  }
+
   void spiBegin() {
     spi_init(_spiChannel, _spiSpeed);
     spi_set_format(_spiChannel, 8, SPI_CPOL_0, SPI_CPHA_0, SPI_MSB_FIRST);
@@ -125,6 +176,10 @@ public:
     spi_write_read_blocking(_spiChannel, out, in, len);
   }
 
+  void yield() override {
+  	tight_loop_contents();
+  }
+
   void spiEndTransaction() {}
 
   void spiEnd() {
@@ -140,4 +195,4 @@ private:
   uint32_t _sckPin;
 };
 
-#endif
+#endif