diff --git a/ports/stm32f4/Makefile b/ports/stm32f4/Makefile
index 4b660f244f..2727ea954f 100755
--- a/ports/stm32f4/Makefile
+++ b/ports/stm32f4/Makefile
@@ -121,7 +121,7 @@ LIBS += -lm
 endif
 
 # TinyUSB defines
-CFLAGS += -DHSE_VALUE=8000000 -DCFG_TUSB_MCU=OPT_MCU_STM32F4 -DCFG_TUD_CDC_RX_BUFSIZE=1024 -DCFG_TUD_CDC_TX_BUFSIZE=1024 -DCFG_TUD_MSC_BUFSIZE=4096 -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_MIDI_TX_BUFSIZE=128
+CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_STM32F4 -DCFG_TUD_CDC_RX_BUFSIZE=1024 -DCFG_TUD_CDC_TX_BUFSIZE=1024 -DCFG_TUD_MSC_BUFSIZE=4096 -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_MIDI_TX_BUFSIZE=128
 
 
 ######################################
diff --git a/ports/stm32f4/boards/feather_f405/stm32f4xx_hal_conf.h b/ports/stm32f4/boards/feather_f405/stm32f4xx_hal_conf.h
index a13e5ecfa3..7a1a9428f8 100644
--- a/ports/stm32f4/boards/feather_f405/stm32f4xx_hal_conf.h
+++ b/ports/stm32f4/boards/feather_f405/stm32f4xx_hal_conf.h
@@ -61,7 +61,7 @@
 /* #define HAL_SD_MODULE_ENABLED   */
 /* #define HAL_MMC_MODULE_ENABLED   */
 #define HAL_SPI_MODULE_ENABLED
-/* #define HAL_TIM_MODULE_ENABLED   */
+#define HAL_TIM_MODULE_ENABLED
 #define HAL_UART_MODULE_ENABLED   
 /* #define HAL_USART_MODULE_ENABLED   */
 /* #define HAL_IRDA_MODULE_ENABLED   */
diff --git a/ports/stm32f4/common-hal/pulseio/PWMOut.c b/ports/stm32f4/common-hal/pulseio/PWMOut.c
index 78f7b212d7..ba5fc06c1d 100644
--- a/ports/stm32f4/common-hal/pulseio/PWMOut.c
+++ b/ports/stm32f4/common-hal/pulseio/PWMOut.c
@@ -4,6 +4,8 @@
  * The MIT License (MIT)
  *
  * Copyright (c) 2018 Dan Halbert for Adafruit Industries
+ * Copyright (c) 2019 Lucian Copeland for Adafruit Industries
+ * Utilizes code from Micropython, Copyright (c) 2013-2016 Damien P. George
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to deal
@@ -29,6 +31,32 @@
 #include "common-hal/pulseio/PWMOut.h"
 #include "shared-bindings/pulseio/PWMOut.h"
 #include "supervisor/shared/translate.h"
+#include "stm32f4xx_hal.h"
+
+#define PWM_MAX_FREQ 1000000
+
+// Get the frequency (in Hz) of the source clock for the given timer.
+// On STM32F405/407/415/417 there are 2 cases for how the clock freq is set.
+// If the APB prescaler is 1, then the timer clock is equal to its respective
+// APB clock.  Otherwise (APB prescaler > 1) the timer clock is twice its
+// respective APB clock.  See DM00031020 Rev 4, page 115.
+static uint32_t timer_get_source_freq(uint32_t tim_id) {
+    uint32_t source, clk_div;
+    if (tim_id == 1 || (8 <= tim_id && tim_id <= 11)) {
+        // TIM{1,8,9,10,11} are on APB2
+        source = HAL_RCC_GetPCLK2Freq();
+        clk_div = RCC->CFGR & RCC_CFGR_PPRE2;
+    } else {
+        // TIM{2,3,4,5,6,7,12,13,14} are on APB1
+        source = HAL_RCC_GetPCLK1Freq();
+        clk_div = RCC->CFGR & RCC_CFGR_PPRE1;
+    }
+    if (clk_div != 0) {
+        // APB prescaler for this timer is > 1
+        source *= 2;
+    }
+    return source;
+}
 
 void pwmout_reset(void) {
 }
@@ -44,29 +72,56 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                                                     uint16_t duty,
                                                     uint32_t frequency,
                                                     bool variable_frequency) {
+    //Using PB08: Tim4 Ch3 for testing
+    int tim_num = 10; 
+    int tim_chan = TIM_CHANNEL_1;
 
-    __HAL_RCC_TIM4_CLK_ENABLE();
+    GPIO_InitTypeDef GPIO_InitStruct = {0};
+    GPIO_InitStruct.Pin = pin_mask(pin->number);
+    GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
+    GPIO_InitStruct.Pull = GPIO_PULLUP;
+    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH;
+    GPIO_InitStruct.Alternate = 3;//2; //2 is timer 4
+    HAL_GPIO_Init(pin_port(pin->port), &GPIO_InitStruct);
+
+    //__HAL_RCC_TIM4_CLK_ENABLE();
+    __HAL_RCC_TIM10_CLK_ENABLE();
+
+    uint32_t source_freq = timer_get_source_freq(tim_num);
+    uint32_t period = PWM_MAX_FREQ/frequency;
+    mp_printf(&mp_plat_print, "SysCoreClock: %d\n", SystemCoreClock);
+    mp_printf(&mp_plat_print, "Source Freq: %d\n", source_freq);
+    mp_printf(&mp_plat_print, "Timer Freq: %d\n", source_freq/(source_freq / PWM_MAX_FREQ));
+    mp_printf(&mp_plat_print, "Actual Freq: %d\n", (source_freq/(source_freq / PWM_MAX_FREQ))/period);
+    mp_printf(&mp_plat_print, "Period: %d\n", (PWM_MAX_FREQ/frequency));
 
     TIM_HandleTypeDef tim = {0};
-    tim.Instance = TIM4;
-    tim.Init.Period = LED_PWM_TIM_PERIOD - 1;
-    tim.Init.Prescaler = timer_get_source_freq(pwm_cfg->tim_id) / 1000000 - 1; // TIM runs at 1MHz
+    tim.Instance = TIM10;
+    tim.Init.Period = period - 1;
+    tim.Init.Prescaler = (source_freq / PWM_MAX_FREQ) - 1; // TIM runs at 16MHz
     tim.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1;
     tim.Init.CounterMode = TIM_COUNTERMODE_UP;
     tim.Init.RepetitionCounter = 0;
-    HAL_TIM_PWM_Init(&tim);
+    if(HAL_TIM_PWM_Init(&tim) == HAL_OK) {
+        mp_printf(&mp_plat_print, "Tim Init Success\n");
+    }
 
     // PWM configuration
     TIM_OC_InitTypeDef oc_init;
     oc_init.OCMode = TIM_OCMODE_PWM1;
-    oc_init.Pulse = 0; // off
-    oc_init.OCPolarity = MICROPY_HW_LED_INVERTED ? TIM_OCPOLARITY_LOW : TIM_OCPOLARITY_HIGH;
+    oc_init.Pulse = (period*duty)/100 - 1;
+    oc_init.OCPolarity = TIM_OCPOLARITY_LOW;
     oc_init.OCFastMode = TIM_OCFAST_DISABLE;
-    oc_init.OCNPolarity = TIM_OCNPOLARITY_HIGH; // needed for TIM1 and TIM8
+    oc_init.OCNPolarity = TIM_OCNPOLARITY_LOW; // needed for TIM1 and TIM8
     oc_init.OCIdleState = TIM_OCIDLESTATE_SET; // needed for TIM1 and TIM8
     oc_init.OCNIdleState = TIM_OCNIDLESTATE_SET; // needed for TIM1 and TIM8
-    HAL_TIM_PWM_ConfigChannel(&tim, &oc_init, pwm_cfg->tim_channel);
-    HAL_TIM_PWM_Start(&tim, pwm_cfg->tim_channel);
+    if(HAL_TIM_PWM_ConfigChannel(&tim, &oc_init, tim_chan) == HAL_OK) {
+        mp_printf(&mp_plat_print, "Channel Config Success\n");
+    }
+    if(HAL_TIM_PWM_Start(&tim, tim_chan) == HAL_OK) {
+        mp_printf(&mp_plat_print, "Start Success\n");
+    }
+
     return PWMOUT_OK;
 }
 
diff --git a/ports/stm32f4/mpconfigport.mk b/ports/stm32f4/mpconfigport.mk
index ffe586898e..bce68f99f4 100644
--- a/ports/stm32f4/mpconfigport.mk
+++ b/ports/stm32f4/mpconfigport.mk
@@ -20,6 +20,7 @@ CIRCUITPY_DIGITALIO = 1
 CIRCUITPY_ANALOGIO = 1
 CIRCUITPY_MICROCONTROLLER = 1
 CIRCUITPY_BUSIO = 1
+CIRCUITPY_PULSEIO = 1
 CIRCUITPY_OS = 1
 CIRCUITPY_STORAGE = 1
 CIRCUITPY_RANDOM = 1