stm32: Add PulseOut support

Matches the implementations of the NRF and Atmel ports. TIM7 is used as it does not have a tied pin. Contains some register micromanagement since HAL support for the TIM7 timer is limited.

ports/stm32f4/common-hal/pulseio/PWMOut.c

@@ -163,7 +163,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
         } else if (var_freq_mismatch) {
             mp_raise_ValueError(translate("Cannot vary frequency on a timer that is already in use"));
         } else {
-            mp_raise_ValueError(translate("Invalid pins"));
+            mp_raise_ValueError(translate("Invalid pins for PWMOut"));
         }
     }
 

ports/stm32f4/common-hal/pulseio/PulseOut.c

@@ -35,21 +35,172 @@
 #include "shared-bindings/pulseio/PWMOut.h"
 #include "supervisor/shared/translate.h"
 
+#include "stm32f4xx_hal.h"
+#include "common-hal/microcontroller/Pin.h"
+#include "tick.h"
+
+// A single timer is shared amongst all PulseOut objects under the assumption that
+// the code is single threaded.
+STATIC uint8_t refcount = 0;
+
+STATIC uint16_t *pulse_array = NULL;
+STATIC volatile uint16_t pulse_array_index = 0;
+STATIC uint16_t pulse_array_length;
+
+//Timer is shared, must be accessible by interrupt
+STATIC TIM_HandleTypeDef t7_handle;
+pulseio_pulseout_obj_t *curr_pulseout = NULL;
+
+STATIC void turn_on(pulseio_pulseout_obj_t *pulseout) {
+    // Turn on PWM
+    HAL_TIM_PWM_Start(&(pulseout->pwmout->handle), pulseout->pwmout->channel);
+}
+
+STATIC void turn_off(pulseio_pulseout_obj_t *pulseout) {
+    // Turn off PWM
+    HAL_TIM_PWM_Stop(&(pulseout->pwmout->handle), pulseout->pwmout->channel);
+    // Make sure pin is low.
+    HAL_GPIO_WritePin(pin_port(pulseout->pwmout->tim->pin->port), 
+                      pin_mask(pulseout->pwmout->tim->pin->number), 0);
+}
+
+STATIC void start_timer(void) {
+    // Set the new period
+    t7_handle.Init.Period = pulse_array[pulse_array_index] - 1;
+    HAL_TIM_Base_Init(&t7_handle);
+
+    // TIM7 has limited HAL support, set registers manually
+    t7_handle.Instance->SR = 0; // Prevent the SR from triggering an interrupt
+    t7_handle.Instance->CR1 |= TIM_CR1_CEN; // Resume timer
+    t7_handle.Instance->CR1 |= TIM_CR1_URS; // Disable non-overflow interrupts
+    __HAL_TIM_ENABLE_IT(&t7_handle, TIM_IT_UPDATE);
+
+}
+
+STATIC void pulseout_event_handler(void) {
+    if (curr_pulseout->pwmout == NULL) {
+        return; //invalid interrupt
+    }
+
+    HAL_GPIO_WritePin(pin_port(2),pin_mask(6), 1);
+    HAL_GPIO_WritePin(pin_port(2),pin_mask(6), 0);
+
+    pulse_array_index++;
+
+    // No more pulses. Turn off output and don't restart.
+    if (pulse_array_index >= pulse_array_length) {
+        turn_off(curr_pulseout);
+        return;
+    }
+
+    // Alternate on and off, starting with on.
+    if (pulse_array_index % 2 == 0) {
+        turn_on(curr_pulseout);
+    } else {
+        turn_off(curr_pulseout);
+    }
+
+    // Count up to the next given value.
+    start_timer();
+}
 
 void pulseout_reset() {
+    __HAL_RCC_TIM7_CLK_DISABLE();
+    refcount = 0;
 }
 
 void common_hal_pulseio_pulseout_construct(pulseio_pulseout_obj_t* self,
                                            const pulseio_pwmout_obj_t* carrier) {
-    mp_raise_NotImplementedError(translate("PulseOut not yet supported"));
+    // Add to active PulseOuts
+    refcount++;
+
+    // Calculate a 1 ms period
+    uint32_t source, clk_div;
+    source = HAL_RCC_GetPCLK1Freq(); // TIM7 is on APB1
+    clk_div = RCC->CFGR & RCC_CFGR_PPRE1;
+    // APB quirk, see See DM00031020 Rev 4, page 115.
+    if (clk_div != 0) {
+        // APB prescaler for this timer is > 1
+        source *= 2;
+    }
+
+    uint32_t prescaler = source/1000000; //1us intervals
+
+    __HAL_RCC_TIM7_CLK_ENABLE();
+    HAL_NVIC_SetPriority(TIM7_IRQn, 4, 0);
+    HAL_NVIC_EnableIRQ(TIM7_IRQn);
+
+    // Timers 6 and 7 have no pins, so using them doesn't affect PWM availability
+    t7_handle.Instance = TIM7;
+    t7_handle.Init.Period = 100; //immediately replaced.
+    t7_handle.Init.Prescaler = prescaler - 1;
+    t7_handle.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
+    t7_handle.Init.CounterMode = TIM_COUNTERMODE_UP;
+    t7_handle.Init.AutoReloadPreload = TIM_AUTORELOAD_PRELOAD_DISABLE;
+
+    HAL_TIM_Base_Init(&t7_handle);
+    t7_handle.Instance->SR = 0;
+
+    // The HAL can't work with const, recast required.
+    self->pwmout = (pulseio_pwmout_obj_t*)carrier;
+
+    turn_off(self);
 }
 
 bool common_hal_pulseio_pulseout_deinited(pulseio_pulseout_obj_t* self) {
-    return true;
+    return self->pwmout == NULL;
 }
 
 void common_hal_pulseio_pulseout_deinit(pulseio_pulseout_obj_t* self) {
+    if (common_hal_pulseio_pulseout_deinited(self)) {
+        return;
+    }
+    turn_on(self);
+    self->pwmout = NULL;
+
+    refcount--;
+    if (refcount == 0) {
+        __HAL_RCC_TIM7_CLK_DISABLE();
+    }
 }
 
 void common_hal_pulseio_pulseout_send(pulseio_pulseout_obj_t* self, uint16_t* pulses, uint16_t length) {
+    pulse_array = pulses;
+    pulse_array_index = 0;
+    pulse_array_length = length;
+    curr_pulseout = self;
+
+    turn_on(self);
+
+    // Count up to the next given value.
+    start_timer();
+
+    // Use when debugging, or issues are irrecoverable
+    // uint32_t starttime = supervisor_ticks_ms64();
+    // uint32_t timeout = 10000;
+    while(pulse_array_index < length) {
+        // Do other things while we wait. The interrupts will handle sending the
+        // signal.
+        RUN_BACKGROUND_TASKS;
+
+        // Use when debugging, or issues are irrecoverable
+        // if ((supervisor_ticks_ms64() - starttime ) > timeout ) {
+        //    mp_raise_RuntimeError(translate("Error: Send Timeout"));
+        // }
+    }
+    //turn off timer counter. 
+    t7_handle.Instance->CR1 &= ~TIM_CR1_CEN;
+}
+
+void TIM7_IRQHandler(void)
+{
+    // Detect TIM Update event
+    if (__HAL_TIM_GET_FLAG(&t7_handle, TIM_FLAG_UPDATE) != RESET)
+    {
+        if (__HAL_TIM_GET_IT_SOURCE(&t7_handle, TIM_IT_UPDATE) != RESET)
+        {
+            __HAL_TIM_CLEAR_IT(&t7_handle, TIM_IT_UPDATE);
+            pulseout_event_handler();
+        }
+    }
 }

ports/stm32f4/common-hal/pulseio/PulseOut.h

@@ -34,7 +34,7 @@
 
 typedef struct {
     mp_obj_base_t base;
-    const pulseio_pwmout_obj_t *pwmout;
+    pulseio_pwmout_obj_t *pwmout;
 } pulseio_pulseout_obj_t;
 
 void pulseout_reset(void);

ports/stm32f4/supervisor/port.c

@@ -35,6 +35,7 @@
 #include "common-hal/busio/SPI.h"
 #include "common-hal/busio/UART.h"
 #include "common-hal/pulseio/PWMOut.h"
+#include "common-hal/pulseio/PulseOut.h"
 
 #include "stm32f4/clocks.h"
 #include "stm32f4/gpio.h"
@@ -60,6 +61,7 @@ void reset_port(void) {
     spi_reset();
     uart_reset();
     pwmout_reset();
+    pulseout_reset();
 }
 
 void reset_to_bootloader(void) {