Add program that is supposed to do CW

11 files changed, 1125 insertions, 0 deletions

diff --git a/src/cw-example/FreeRTOS b/src/cw-example/FreeRTOS
new file mode 120000
index 0000000..51f4e96
--- /dev/null
+++ b/src/cw-example/FreeRTOS
@@ -0,0 +1 @@
+../FreeRTOS
\ No newline at end of file
diff --git a/src/cw-example/FreeRTOSConfig.h b/src/cw-example/FreeRTOSConfig.h
new file mode 100644
index 0000000..0096216
--- /dev/null
+++ b/src/cw-example/FreeRTOSConfig.h
@@ -0,0 +1,165 @@
+/*

+    FreeRTOS V8.0.0:rc2 - Copyright (C) 2014 Real Time Engineers Ltd. 

+    All rights reserved

+

+    VISIT http://www.FreeRTOS.org TO ENSURE YOU ARE USING THE LATEST VERSION.

+

+    ***************************************************************************

+     *                                                                       *

+     *    FreeRTOS provides completely free yet professionally developed,    *

+     *    robust, strictly quality controlled, supported, and cross          *

+     *    platform software that has become a de facto standard.             *

+     *                                                                       *

+     *    Help yourself get started quickly and support the FreeRTOS         *

+     *    project by purchasing a FreeRTOS tutorial book, reference          *

+     *    manual, or both from: http://www.FreeRTOS.org/Documentation        *

+     *                                                                       *

+     *    Thank you!                                                         *

+     *                                                                       *

+    ***************************************************************************

+

+    This file is part of the FreeRTOS distribution.

+

+    FreeRTOS is free software; you can redistribute it and/or modify it under

+    the terms of the GNU General Public License (version 2) as published by the

+    Free Software Foundation >>!AND MODIFIED BY!<< the FreeRTOS exception.

+

+    >>! NOTE: The modification to the GPL is included to allow you to distribute

+    >>! a combined work that includes FreeRTOS without being obliged to provide

+    >>! the source code for proprietary components outside of the FreeRTOS

+    >>! kernel.

+

+    FreeRTOS is distributed in the hope that it will be useful, but WITHOUT ANY

+    WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS

+    FOR A PARTICULAR PURPOSE.  Full license text is available from the following

+    link: http://www.freertos.org/a00114.html

+

+    1 tab == 4 spaces!

+

+    ***************************************************************************

+     *                                                                       *

+     *    Having a problem?  Start by reading the FAQ "My application does   *

+     *    not run, what could be wrong?"                                     *

+     *                                                                       *

+     *    http://www.FreeRTOS.org/FAQHelp.html                               *

+     *                                                                       *

+    ***************************************************************************

+

+    http://www.FreeRTOS.org - Documentation, books, training, latest versions,

+    license and Real Time Engineers Ltd. contact details.

+

+    http://www.FreeRTOS.org/plus - A selection of FreeRTOS ecosystem products,

+    including FreeRTOS+Trace - an indispensable productivity tool, a DOS

+    compatible FAT file system, and our tiny thread aware UDP/IP stack.

+

+    http://www.OpenRTOS.com - Real Time Engineers ltd license FreeRTOS to High

+    Integrity Systems to sell under the OpenRTOS brand.  Low cost OpenRTOS

+    licenses offer ticketed support, indemnification and middleware.

+

+    http://www.SafeRTOS.com - High Integrity Systems also provide a safety

+    engineered and independently SIL3 certified version for use in safety and

+    mission critical applications that require provable dependability.

+

+    1 tab == 4 spaces!

+*/

+

+

+#ifndef FREERTOS_CONFIG_H

+#define FREERTOS_CONFIG_H

+

+/*-----------------------------------------------------------

+ * Application specific definitions.

+ *

+ * These definitions should be adjusted for your particular hardware and

+ * application requirements.

+ *

+ * THESE PARAMETERS ARE DESCRIBED WITHIN THE 'CONFIGURATION' SECTION OF THE

+ * FreeRTOS API DOCUMENTATION AVAILABLE ON THE FreeRTOS.org WEB SITE.

+ *

+ * See http://www.freertos.org/a00110.html.

+ *----------------------------------------------------------*/

+

+/* Ensure stdint is only used by the compiler, and not the assembler. */

+//#ifdef __ICCARM__

+	#include <stdint.h>

+	extern uint32_t SystemCoreClock;

+//#endif

+

+#define configUSE_PREEMPTION			1

+#define configUSE_IDLE_HOOK				0 // Default: 1

+#define configUSE_TICK_HOOK				0 // Default: 1

+#define configCPU_CLOCK_HZ				( SystemCoreClock )

+#define configTICK_RATE_HZ				( ( portTickType ) 1000 )

+#define configMAX_PRIORITIES			( 5 )

+#define configMINIMAL_STACK_SIZE		( ( unsigned short ) 130 )

+#define configTOTAL_HEAP_SIZE			( ( size_t ) ( 75 * 1024 ) )

+#define configMAX_TASK_NAME_LEN			( 10 )

+#define configUSE_TRACE_FACILITY		1

+#define configUSE_16_BIT_TICKS			0

+#define configIDLE_SHOULD_YIELD			1

+#define configUSE_MUTEXES				1

+#define configQUEUE_REGISTRY_SIZE		8

+#define configCHECK_FOR_STACK_OVERFLOW	0 // Default: 2

+#define configUSE_RECURSIVE_MUTEXES		1

+#define configUSE_MALLOC_FAILED_HOOK	0 // Default: 1

+#define configUSE_APPLICATION_TASK_TAG	0

+#define configUSE_COUNTING_SEMAPHORES	1

+#define configGENERATE_RUN_TIME_STATS	0

+

+/* Co-routine definitions. */

+#define configUSE_CO_ROUTINES 		0

+#define configMAX_CO_ROUTINE_PRIORITIES ( 2 )

+

+/* Software timer definitions. */

+#define configUSE_TIMERS				1

+#define configTIMER_TASK_PRIORITY		( 2 )

+#define configTIMER_QUEUE_LENGTH		10

+#define configTIMER_TASK_STACK_DEPTH	( configMINIMAL_STACK_SIZE * 2 )

+

+/* Set the following definitions to 1 to include the API function, or zero

+to exclude the API function. */

+#define INCLUDE_vTaskPrioritySet		1

+#define INCLUDE_uxTaskPriorityGet		1

+#define INCLUDE_vTaskDelete				1

+#define INCLUDE_vTaskCleanUpResources	1

+#define INCLUDE_vTaskSuspend			1

+#define INCLUDE_vTaskDelayUntil			1

+#define INCLUDE_vTaskDelay				1

+

+/* Cortex-M specific definitions. */

+#ifdef __NVIC_PRIO_BITS

+	/* __BVIC_PRIO_BITS will be specified when CMSIS is being used. */

+	#define configPRIO_BITS       		__NVIC_PRIO_BITS

+#else

+	#define configPRIO_BITS       		4        /* 15 priority levels */

+#endif

+

+/* The lowest interrupt priority that can be used in a call to a "set priority"

+function. */

+#define configLIBRARY_LOWEST_INTERRUPT_PRIORITY			0xf

+

+/* The highest interrupt priority that can be used by any interrupt service

+routine that makes calls to interrupt safe FreeRTOS API functions.  DO NOT CALL

+INTERRUPT SAFE FREERTOS API FUNCTIONS FROM ANY INTERRUPT THAT HAS A HIGHER

+PRIORITY THAN THIS! (higher priorities are lower numeric values. */

+#define configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY	5

+

+/* Interrupt priorities used by the kernel port layer itself.  These are generic

+to all Cortex-M ports, and do not rely on any particular library functions. */

+#define configKERNEL_INTERRUPT_PRIORITY 		( configLIBRARY_LOWEST_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )

+/* !!!! configMAX_SYSCALL_INTERRUPT_PRIORITY must not be set to zero !!!!

+See http://www.FreeRTOS.org/RTOS-Cortex-M3-M4.html. */

+#define configMAX_SYSCALL_INTERRUPT_PRIORITY 	( configLIBRARY_MAX_SYSCALL_INTERRUPT_PRIORITY << (8 - configPRIO_BITS) )

+	

+/* Normal assert() semantics without relying on the provision of an assert.h

+header file. */

+#define configASSERT( x ) if( ( x ) == 0 ) { taskDISABLE_INTERRUPTS(); for( ;; ); }	

+	

+/* Definitions that map the FreeRTOS port interrupt handlers to their CMSIS

+standard names. */

+#define vPortSVCHandler SVC_Handler

+#define xPortPendSVHandler PendSV_Handler

+#define xPortSysTickHandler SysTick_Handler

+

+#endif /* FREERTOS_CONFIG_H */

+

diff --git a/src/cw-example/Makefile b/src/cw-example/Makefile
new file mode 100644
index 0000000..aa8926d
--- /dev/null
+++ b/src/cw-example/Makefile
@@ -0,0 +1,119 @@
+###
+# GNU ARM Embedded Toolchain
+CC=arm-none-eabi-gcc
+LD=arm-none-eabi-ld
+AR=arm-none-eabi-ar
+AS=arm-none-eabi-as
+CP=arm-none-eabi-objcopy
+OD=arm-none-eabi-objdump
+SIZE=arm-none-eabi-size
+
+###
+# Directory Structure
+BINDIR=bin
+SRCDIR=.
+
+###
+# Find source files
+ASOURCES=$(shell find -L $(SRCDIR) -name '*.s')
+CSOURCES+=$(shell find -L $(SRCDIR) -name '*.c')
+# Find header directories
+INC=$(shell find -L . -name '*.h' -exec dirname {} \; | uniq)
+INCLUDES=$(INC:%=-I%)
+# Create object list
+OBJECTS=$(ASOURCES:%.s=%.o)
+OBJECTS+=$(CSOURCES:%.c=%.o)
+# Define output files ELF & IHEX
+BINELF=outp.elf
+BINHEX=outp.hex
+
+###
+# MCU FLAGS
+MCFLAGS=-mcpu=cortex-m4 -mthumb -mlittle-endian \
+-mfpu=fpv4-sp-d16 -mfloat-abi=softfp -mthumb-interwork
+# COMPILE FLAGS
+DEFS=-DUSE_STDPERIPH_DRIVER -DSTM32F4XX -DARM_MATH_CM4 -D__FPU_PRESENT=1
+CFLAGS  =-Wall -ggdb -std=c99 -c $(MCFLAGS) $(DEFS) $(INCLUDES)
+# LINKER FLAGS
+LDSCRIPT= bsp/stm32_flash.ld
+LDFLAGS =-T $(LDSCRIPT) --specs=nosys.specs $(MCFLAGS)
+
+###
+# Optimizations
+OPT?='O1 O2 O3 O4 O6 O7' # O5 disabled by default, because it breaks code
+
+ifneq ($(findstring release-memopt,$(MAKECMDGOALS)),)
+ifneq ($(filter O1,$(OPT)),)
+CXXFLAGS+=-fno-exceptions # Uncomment to disable exception handling
+DEFS+=-DNO_EXCEPTIONS # The source code has to comply with this rule
+endif
+
+ifneq ($(filter O2,$(OPT)),)
+CFLAGS+=-Os # Optimize for size https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
+CXXFLAGS+=-Os
+LDFLAGS+=-Os # Optimize for size https://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html
+endif
+
+ifneq ($(filter O3,$(OPT)),)
+CFLAGS+=-ffunction-sections -fdata-sections # Place each function or data item into its own section in the output file
+CXXFLAGS+=-ffunction-sections -fdata-sections # -||-
+LDFLAGS+=-Wl,-gc-sections # Remove isolated unused sections
+endif
+
+ifneq ($(filter O4,$(OPT)),)
+CFLAGS+=-fno-builtin # Disable C++ exception handling
+CXXFLAGS+=-fno-builtin # Disable C++ exception handling
+endif
+
+ifneq ($(filter O5,$(OPT)),)
+CFLAGS+=-flto # Enable link time optimization
+CXXFLAGS+=-flto # Enable link time optimization
+LDFLAGS+=-flto # Enable link time optimization
+endif
+
+ifneq ($(filter O6,$(OPT)),)
+CXXFLAGS+=-fno-rtti # Disable type introspection
+endif
+
+ifneq ($(findstring O7,$(OPT)),)
+LDFLAGS+=--specs=nano.specs # Use size optimized newlib
+endif
+endif
+
+###
+# Build Rules
+.PHONY: all release release-memopt debug clean
+
+all: release
+
+release: $(BINDIR)/$(BINHEX)
+
+release-memopt: release
+
+debug: CFLAGS+=-g
+debug: LDFLAGS+=-g
+debug: release
+
+$(BINDIR)/$(BINHEX): $(BINDIR)/$(BINELF)
+	$(CP) -O ihex $< $@
+
+$(BINDIR)/$(BINELF): $(OBJECTS)
+	$(CC) $(LDFLAGS) $(OBJECTS) -o $@
+	$(SIZE) $(BINDIR)/$(BINELF)
+
+%.o: %.c
+	$(CC) $(CFLAGS) $< -o $@
+
+%.o: %.s
+	$(CC) $(CFLAGS) $< -o $@
+
+clean:
+	rm -f $(OBJECTS) $(BINDIR)/$(BINELF) $(BINDIR)/$(BINHEX)
+
+# Connect to openocd's gdb server on port 3333
+deploy:
+ifeq ($(wildcard /opt/openocd/bin/openocd),)
+	/usr/bin/openocd -f /usr/share/openocd/scripts/board/stm32f4discovery.cfg -c "program bin/"$(BINELF)" verify reset" -c "init" -c "reset halt"
+else
+	/opt/openocd/bin/openocd -f /opt/openocd/share/openocd/scripts/board/stm32f4discovery.cfg -c "program bin/"$(BINELF)" verify reset" -c "init" -c "reset halt"
+endif
diff --git a/src/cw-example/README.md b/src/cw-example/README.md
new file mode 100644
index 0000000..5a75a32
--- /dev/null
+++ b/src/cw-example/README.md
@@ -0,0 +1,2 @@
+An example program that tries to output CW using
+the audio codec on the STM32F4DISCOVERY.
diff --git a/src/cw-example/audio.c b/src/cw-example/audio.c
new file mode 100644
index 0000000..1f16edc
--- /dev/null
+++ b/src/cw-example/audio.c
@@ -0,0 +1,285 @@
+#include "audio.h"
+#include "stm32f4xx_conf.h"
+#include "stm32f4xx.h"
+
+#include <stdlib.h>
+
+static void WriteRegister(uint8_t address, uint8_t value);
+static void StartAudioDMAAndRequestBuffers();
+static void StopAudioDMA();
+
+static AudioCallbackFunction *CallbackFunction;
+static void *CallbackContext;
+static int16_t * volatile NextBufferSamples;
+static volatile int NextBufferLength;
+static volatile int BufferNumber;
+static volatile bool DMARunning;
+
+void InitializeAudio(int plln, int pllr, int i2sdiv, int i2sodd) {
+    GPIO_InitTypeDef  GPIO_InitStructure;
+
+    // Intitialize state.
+    CallbackFunction = NULL;
+    CallbackContext = NULL;
+    NextBufferSamples = NULL;
+    NextBufferLength = 0;
+    BufferNumber = 0;
+    DMARunning = false;
+
+    // Turn on peripherals.
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOB, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOC, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_DMA1, ENABLE);
+
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_I2C1, ENABLE);
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_SPI3, ENABLE);
+
+    // Configure reset pin.
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_Init(GPIOD, &GPIO_InitStructure);
+
+    // Configure I2C SCL and SDA pins.
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_6 | GPIO_Pin_9;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_OD;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_Init(GPIOB, &GPIO_InitStructure);
+
+    GPIO_PinAFConfig(GPIOB, GPIO_PinSource6, GPIO_AF_I2C1);
+    GPIO_PinAFConfig(GPIOB, GPIO_PinSource9, GPIO_AF_I2C1);
+
+    // Configure I2S MCK, SCK, SD pins.
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_7 | GPIO_Pin_10 | GPIO_Pin_12;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_Init(GPIOC, &GPIO_InitStructure);
+
+    GPIO_PinAFConfig(GPIOC, GPIO_PinSource7, GPIO_AF_SPI3);
+    GPIO_PinAFConfig(GPIOC, GPIO_PinSource10, GPIO_AF_SPI3);
+    GPIO_PinAFConfig(GPIOC, GPIO_PinSource12, GPIO_AF_SPI3);
+
+    // Configure I2S WS pin.
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_4;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_50MHz;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_Init(GPIOA, &GPIO_InitStructure);
+
+    GPIO_PinAFConfig(GPIOA, GPIO_PinSource4, GPIO_AF_SPI3);
+
+    // Reset the codec.
+    GPIOD ->BSRRH = 1 << 4;
+    for (volatile int i = 0; i < 0x4fff; i++) {
+        __asm__ volatile("nop");
+    }
+    GPIOD ->BSRRL = 1 << 4;
+
+    // Reset I2C.
+    RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C1, ENABLE);
+    RCC_APB1PeriphResetCmd(RCC_APB1Periph_I2C1, DISABLE);
+
+    // Configure I2C.
+    uint32_t pclk1 = 42000000;
+
+    I2C1 ->CR2 = pclk1 / 1000000; // Configure frequency and disable interrupts and DMA.
+    I2C1 ->OAR1 = I2C_OAR1_ADDMODE | 0x33;
+
+    // Configure I2C speed in standard mode.
+    const uint32_t i2c_speed = 100000;
+    int ccrspeed = pclk1 / (i2c_speed * 2);
+    if (ccrspeed < 4) {
+        ccrspeed = 4;
+    }
+    I2C1 ->CCR = ccrspeed;
+    I2C1 ->TRISE = pclk1 / 1000000 + 1;
+
+    I2C1 ->CR1 = I2C_CR1_ACK | I2C_CR1_PE; // Enable and configure the I2C peripheral.
+
+    // Configure codec.
+    WriteRegister(0x02, 0x01); // Keep codec powered off.
+    WriteRegister(0x04, 0xaf); // SPK always off and HP always on.
+
+    WriteRegister(0x05, 0x81); // Clock configuration: Auto detection.
+    WriteRegister(0x06, 0x04); // Set slave mode and Philips audio standard.
+
+    SetAudioVolume(0xff);
+
+    // Power on the codec.
+    WriteRegister(0x02, 0x9e);
+
+    // Configure codec for fast shutdown.
+    WriteRegister(0x0a, 0x00); // Disable the analog soft ramp.
+    WriteRegister(0x0e, 0x04); // Disable the digital soft ramp.
+
+    WriteRegister(0x27, 0x00); // Disable the limiter attack level.
+    WriteRegister(0x1f, 0x0f); // Adjust bass and treble levels.
+
+    WriteRegister(0x1a, 0x0a); // Adjust PCM volume level.
+    WriteRegister(0x1b, 0x0a);
+
+    // Disable I2S.
+    SPI3 ->I2SCFGR = 0;
+
+    // I2S clock configuration
+    RCC ->CFGR &= ~RCC_CFGR_I2SSRC; // PLLI2S clock used as I2S clock source.
+    RCC ->PLLI2SCFGR = (pllr << 28) | (plln << 6);
+
+    // Enable PLLI2S and wait until it is ready.
+    RCC ->CR |= RCC_CR_PLLI2SON;
+    while (!(RCC ->CR & RCC_CR_PLLI2SRDY ))
+        ;
+
+    // Configure I2S.
+    SPI3 ->I2SPR = i2sdiv | (i2sodd << 8) | SPI_I2SPR_MCKOE;
+    SPI3 ->I2SCFGR = SPI_I2SCFGR_I2SMOD | SPI_I2SCFGR_I2SCFG_1
+        | SPI_I2SCFGR_I2SE; // Master transmitter, Phillips mode, 16 bit values, clock polarity low, enable.
+
+}
+
+void AudioOn() {
+    WriteRegister(0x02, 0x9e);
+    SPI3 ->I2SCFGR = SPI_I2SCFGR_I2SMOD | SPI_I2SCFGR_I2SCFG_1
+        | SPI_I2SCFGR_I2SE; // Master transmitter, Phillips mode, 16 bit values, clock polarity low, enable.
+}
+
+void AudioOff() {
+    WriteRegister(0x02, 0x01);
+    SPI3 ->I2SCFGR = 0;
+}
+
+void SetAudioVolume(int volume) {
+    WriteRegister(0x20, (volume + 0x19) & 0xff);
+    WriteRegister(0x21, (volume + 0x19) & 0xff);
+}
+
+void OutputAudioSample(int16_t sample) {
+    while (!(SPI3 ->SR & SPI_SR_TXE ))
+        ;
+    SPI3 ->DR = sample;
+}
+
+void OutputAudioSampleWithoutBlocking(int16_t sample) {
+    SPI3 ->DR = sample;
+}
+
+void PlayAudioWithCallback(AudioCallbackFunction *callback, void *context) {
+    StopAudioDMA();
+
+    NVIC_EnableIRQ(DMA1_Stream7_IRQn);
+    NVIC_SetPriority(DMA1_Stream7_IRQn, 4);
+
+    SPI3 ->CR2 |= SPI_CR2_TXDMAEN; // Enable I2S TX DMA request.
+
+    CallbackFunction = callback;
+    CallbackContext = context;
+    BufferNumber = 0;
+
+    if (CallbackFunction)
+        CallbackFunction(CallbackContext, BufferNumber);
+}
+
+void StopAudio() {
+    StopAudioDMA();
+    SPI3 ->CR2 &= ~SPI_CR2_TXDMAEN; // Disable I2S TX DMA request.
+    NVIC_DisableIRQ(DMA1_Stream7_IRQn);
+    CallbackFunction = NULL;
+}
+
+void ProvideAudioBuffer(void *samples, int numsamples) {
+    while (!ProvideAudioBufferWithoutBlocking(samples, numsamples))
+        __asm__ volatile ("wfi");
+}
+
+bool ProvideAudioBufferWithoutBlocking(void *samples, int numsamples) {
+    if (NextBufferSamples)
+        return false;
+
+    NVIC_DisableIRQ(DMA1_Stream7_IRQn);
+
+    NextBufferSamples = samples;
+    NextBufferLength = numsamples;
+
+    if (!DMARunning)
+        StartAudioDMAAndRequestBuffers();
+
+    NVIC_EnableIRQ(DMA1_Stream7_IRQn);
+
+    return true;
+}
+
+static void WriteRegister(uint8_t address, uint8_t value) {
+    while (I2C1 ->SR2 & I2C_SR2_BUSY )
+        ;
+
+    I2C1 ->CR1 |= I2C_CR1_START; // Start the transfer sequence.
+    while (!(I2C1 ->SR1 & I2C_SR1_SB ))
+        ; // Wait for start bit.
+
+    I2C1 ->DR = 0x94;
+    while (!(I2C1 ->SR1 & I2C_SR1_ADDR ))
+        ; // Wait for master transmitter mode.
+    I2C1 ->SR2;
+
+    I2C1 ->DR = address; // Transmit the address to write to.
+    while (!(I2C1 ->SR1 & I2C_SR1_TXE ))
+        ; // Wait for byte to move to shift register.
+
+    I2C1 ->DR = value; // Transmit the value.
+
+    while (!(I2C1 ->SR1 & I2C_SR1_BTF ))
+        ; // Wait for all bytes to finish.
+    I2C1 ->CR1 |= I2C_CR1_STOP; // End the transfer sequence.
+}
+
+static void StartAudioDMAAndRequestBuffers() {
+    // Configure DMA stream.
+    DMA1_Stream7 ->CR = (0 * DMA_SxCR_CHSEL_0 ) | // Channel 0
+        (1 * DMA_SxCR_PL_0 ) | // Priority 1
+        (1 * DMA_SxCR_PSIZE_0 ) | // PSIZE = 16 bit
+        (1 * DMA_SxCR_MSIZE_0 ) | // MSIZE = 16 bit
+        DMA_SxCR_MINC | // Increase memory address
+        (1 * DMA_SxCR_DIR_0 ) | // Memory to peripheral
+        DMA_SxCR_TCIE; // Transfer complete interrupt
+    DMA1_Stream7 ->NDTR = NextBufferLength;
+    DMA1_Stream7 ->PAR = (uint32_t) &SPI3 ->DR;
+    DMA1_Stream7 ->M0AR = (uint32_t) NextBufferSamples;
+    DMA1_Stream7 ->FCR = DMA_SxFCR_DMDIS;
+    DMA1_Stream7 ->CR |= DMA_SxCR_EN;
+
+    // Update state.
+    NextBufferSamples = NULL;
+    BufferNumber ^= 1;
+    DMARunning = true;
+
+    // Invoke callback if it exists to queue up another buffer.
+    if (CallbackFunction)
+        CallbackFunction(CallbackContext, BufferNumber);
+}
+
+static void StopAudioDMA() {
+    DMA1_Stream7 ->CR &= ~DMA_SxCR_EN; // Disable DMA stream.
+    while (DMA1_Stream7 ->CR & DMA_SxCR_EN )
+        ; // Wait for DMA stream to stop.
+
+    DMARunning = false;
+}
+
+void DMA1_Stream7_IRQHandler() {
+    DMA1 ->HIFCR |= DMA_HIFCR_CTCIF7; // Clear interrupt flag.
+
+    if (NextBufferSamples) {
+        StartAudioDMAAndRequestBuffers();
+    } else {
+        DMARunning = false;
+    }
+}
diff --git a/src/cw-example/audio.h b/src/cw-example/audio.h
new file mode 100644
index 0000000..31cb0fe
--- /dev/null
+++ b/src/cw-example/audio.h
@@ -0,0 +1,47 @@
+#ifndef __AUDIO_H__
+#define __AUDIO_H__
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef void AudioCallbackFunction(void *context,int buffer);
+
+#define Audio8000HzSettings 256,5,12,1
+#define Audio16000HzSettings 213,2,13,0
+#define Audio32000HzSettings 213,2,6,1
+#define Audio48000HzSettings 258,3,3,1
+#define Audio96000HzSettings 344,2,3,1
+#define Audio22050HzSettings 429,4,9,1
+#define Audio44100HzSettings 271,2,6,0
+#define AudioVGAHSyncSettings 419,2,13,0 // 31475.3606. Actual VGA timer is 31472.4616.
+
+// Initialize and power up audio hardware. Use the above defines for the parameters.
+// Can probably only be called once.
+void InitializeAudio(int plln,int pllr,int i2sdiv,int i2sodd);
+
+// Power up and down the audio hardware.
+void AudioOn();
+void AudioOff();
+
+// Set audio volume in steps of 0.5 dB. 0xff is +12 dB.
+void SetAudioVolume(int volume);
+
+// Output one audio sample directly to the hardware without using DMA.
+void OutputAudioSample(int16_t sample);
+void OutputAudioSampleWithoutBlocking(int16_t sample);
+
+// Start and stop audio playback using DMA.
+// Callback is optional, and called whenever a new buffer is needed.
+void PlayAudioWithCallback(AudioCallbackFunction *callback,void *context);
+void StopAudio();
+
+// Provide a new buffer to the audio DMA. Output is double buffered, so
+// at least two buffers must be maintained by the program. It is not allowed
+// to overwrite the previously provided buffer until after the next callback
+// invocation.
+// Buffers must reside in DMA1-accessible memory, that is, the 128k RAM bank,
+// or flash.
+void ProvideAudioBuffer(void *samples,int numsamples);
+bool ProvideAudioBufferWithoutBlocking(void *samples,int numsamples);
+
+#endif
diff --git a/src/cw-example/bin/.git_keep b/src/cw-example/bin/.git_keep
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/src/cw-example/bin/.git_keep
diff --git a/src/cw-example/bsp b/src/cw-example/bsp
new file mode 120000
index 0000000..5d9120a
--- /dev/null
+++ b/src/cw-example/bsp
@@ -0,0 +1 @@
+../bsp
\ No newline at end of file
diff --git a/src/cw-example/cw.c b/src/cw-example/cw.c
new file mode 100644
index 0000000..23f8717
--- /dev/null
+++ b/src/cw-example/cw.c
@@ -0,0 +1,259 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Matthias P. Braendli
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+*/
+
+#include "cw.h"
+#include "arm_math.h"
+#include "audio.h"
+
+/* Kernel includes. */
+#include "FreeRTOS.h"
+#include "queue.h"
+#include "semphr.h"
+
+#define ON_BUFFER_SIZE 1024
+
+struct cw_out_message_s {
+    // Contains a sequence of ones and zeros corresponding to
+    // TX on/TX off CW data to be sent
+    uint8_t on_buffer[ON_BUFFER_SIZE];
+    size_t  on_buffer_end;
+
+    int     freq;
+    int     dit_duration;
+};
+
+// The queue contains above structs
+QueueHandle_t cw_queue;
+static int    cw_samplerate;
+
+// The message being currently handled by cw_fill_buffer
+static struct cw_out_message_s cw_fill_msg_current;
+// Set to 1 if the cw_fill_buffer function is currently handling
+// msg_current. 0 if it has to wait for a new message.
+static int    cw_fill_msg_status;
+
+// Keep track of number of audio samples that were already
+// generated from the current message
+static int    cw_fill_audio_sent;
+
+
+void cw_init(unsigned int samplerate)
+{
+    cw_samplerate = samplerate;
+
+    cw_fill_msg_status = 0;
+
+    cw_queue = xQueueCreate(15, sizeof(struct cw_out_message_s));
+    if (cw_queue == 0) {
+        while(1); /* fatal error */
+    }
+}
+
+const uint8_t cw_mapping[60] = { // {{{
+    // Read bits from right to left
+
+    0b110101, //+ ASCII 43
+    0b110101, //, ASCII 44
+    0b1011110, //- ASCII 45
+
+    0b1010101, //., ASCII 46
+    0b110110, // / ASCII 47
+
+    0b100000, // 0, ASCII 48
+    0b100001, // 1
+    0b100011,
+    0b100111,
+    0b101111,
+    0b111111,
+    0b111110,
+    0b111100,
+    0b111000,
+    0b110000, // 9, ASCII 57
+
+    // The following are mostly invalid, but
+    // required to fill the gap in ASCII between
+    // numerals and capital letters
+    0b10, // :
+    0b10, // ;
+    0b10, // <
+    0b10, // =
+    0b10, // >
+    0b1110011, // ?
+    0b1101001, //@
+
+    0b101, // A  ASCII 65
+    0b11110,
+    0b11010,
+    0b1110,
+    0b11,
+    0b11011,
+    0b1100,
+    0b11111,
+    0b111,
+    0b10001,
+    0b1010,
+    0b11101,
+    0b100, //M
+    0b110,
+    0b1000,
+    0b11001,
+    0b10100,
+    0b1101,
+    0b1111,
+    0b10,
+    0b1011,
+    0b10111,
+    0b1001,
+    0b10110,
+    0b10010,
+    0b11100, // Z
+
+    0b101010, //Start, ASCII [
+    0b1010111, // SK , ASCII '\'
+}; //}}}
+
+void cw_symbol(uint8_t sym, struct cw_out_message_s *msg)
+{
+    uint8_t p = 0;
+    uint8_t val = cw_mapping[sym];
+
+    while((val >> p) != 0b1) {
+
+        if (((val >> p) & 0b1) == 0b1) {
+            if (msg->on_buffer_end + 2 < ON_BUFFER_SIZE) {
+                // tone(1)
+                msg->on_buffer[msg->on_buffer_end++] = 1;
+
+                // silence(1)
+                msg->on_buffer[msg->on_buffer_end++] = 0;
+            }
+        }
+        else {
+            if (msg->on_buffer_end + 4 < ON_BUFFER_SIZE) {
+                // tone(3)
+                msg->on_buffer[msg->on_buffer_end++] = 1;
+                msg->on_buffer[msg->on_buffer_end++] = 1;
+                msg->on_buffer[msg->on_buffer_end++] = 1;
+
+                // silence(1)
+                msg->on_buffer[msg->on_buffer_end++] = 0;
+            }
+        }
+
+        p++;
+    }
+
+    // silence(4)
+    if (msg->on_buffer_end + 4 < ON_BUFFER_SIZE) {
+        for (int i = 0; i < 4; i++) {
+            msg->on_buffer[msg->on_buffer_end++] = 0;
+        }
+    }
+}
+
+// Transmit a string in morse code. Supported range:
+// All ASCII between '+' and '\', which includes
+// numerals and capital letters.
+void cw_push_message(const char* text, int dit_duration, int frequency)
+{
+    struct cw_out_message_s msg;
+    msg.freq = frequency;
+    msg.dit_duration = dit_duration;
+
+    const char* sym = text;
+    do {
+        if (*sym < '+' || *sym > '\\') {
+            if (msg.on_buffer_end + 4 < ON_BUFFER_SIZE) {
+                for (int i = 0; i < 4; i++) {
+                    msg.on_buffer[msg.on_buffer_end++] = 0;
+                }
+            }
+        }
+        else {
+            cw_symbol(*sym - '+', &msg);
+        }
+        sym++;
+    } while (*sym != '\0');
+
+    xQueueSendToBack(cw_queue, &msg, 0); /* Send Message */
+}
+
+
+size_t cw_fill_buffer(int16_t *buf, size_t bufsize)
+{
+    if (cw_fill_msg_status == 0) {
+        if (xQueueReceiveFromISR(cw_queue, &cw_fill_msg_current, NULL)) {
+            // Convert msg to audio samples and transmit
+            cw_fill_msg_status = 1;
+            cw_fill_audio_sent = 0;
+        }
+        else {
+            return 0;
+        }
+    }
+
+    const int samples_per_dit = (cw_samplerate * 1000) /
+        cw_fill_msg_current.dit_duration;
+
+    // Angular frequency of NCO
+    const float omega = 2 * FLOAT_PI * cw_fill_msg_current.freq /
+        (float)cw_samplerate;
+
+    // Define start point
+    int start_i = cw_fill_audio_sent / samples_per_dit;
+    int start_t = cw_fill_audio_sent % samples_per_dit;
+
+    for (int i = start_i; i < cw_fill_msg_current.on_buffer_end; i++) {
+
+        for (int t = start_t; t < samples_per_dit; t++) {
+            int16_t s = 0;
+
+            if (cw_fill_msg_current.on_buffer[i]) {
+                s = 32768.0f * arm_sin_f32(omega * t);
+            }
+
+            if (i + 2 >= bufsize) {
+                goto cw_fill_buf_full;
+            }
+
+            // Stereo
+            buf[i++] = s;
+            buf[i++] = s;
+
+            OutputAudioSample(s);
+            OutputAudioSample(s);
+
+            cw_fill_audio_sent += 2;
+        }
+
+        start_t = 0;
+    }
+
+    // We have completed this message
+    cw_fill_msg_status = 0;
+
+cw_fill_buf_full:
+    return bufsize;
+}
+
diff --git a/src/cw-example/cw.h b/src/cw-example/cw.h
new file mode 100644
index 0000000..b090a04
--- /dev/null
+++ b/src/cw-example/cw.h
@@ -0,0 +1,41 @@
+/*
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2015 Matthias P. Braendli
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all
+ * copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+*/
+
+#include <stdint.h>
+#include <stddef.h>
+
+#define FLOAT_PI 3.1415926535897932384f
+
+// Setup the CW generator to create audio samples at the given
+// samplerate.
+void cw_init(unsigned int samplerate);
+
+// Append new CW text to transmit
+// dit_duration in ms
+// frequency in Hz
+void cw_push_message(const char* text, int dit_duration, int frequency);
+
+// Write the waveform into the buffer (stereo)
+size_t cw_fill_buffer(int16_t *buf, size_t bufsize);
+
diff --git a/src/cw-example/main.c b/src/cw-example/main.c
new file mode 100644
index 0000000..ce1f9c6
--- /dev/null
+++ b/src/cw-example/main.c
@@ -0,0 +1,205 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <math.h>
+#include "stm32f4xx_conf.h"
+#include "audio.h"
+
+/* Kernel includes. */
+#include "FreeRTOS.h"
+#include "task.h"
+#include "timers.h"
+#include "semphr.h"
+
+#include "cw.h"
+
+// Private variables
+volatile uint32_t time_var1, time_var2;
+
+// Private function prototypes
+void init();
+
+// Tasks
+static void detect_button_press(void *pvParameters);
+static void audio_task(void *pvParameters);
+
+struct cw_msg_s {
+    const char* msg;
+    int freq;
+    int dit_duration;
+};
+
+int main(void) {
+    init();
+
+    cw_init(16000);
+
+    InitializeAudio(Audio16000HzSettings);
+    SetAudioVolume(128);
+
+    xTaskCreate(
+            detect_button_press,
+            "TaskButton",
+            configMINIMAL_STACK_SIZE,
+            (void*) NULL,
+            tskIDLE_PRIORITY + 2UL,
+            NULL);
+
+    xTaskCreate(
+            audio_task,
+            "TaskAudio",
+            configMINIMAL_STACK_SIZE,
+            (void*) NULL,
+            tskIDLE_PRIORITY + 2UL,
+            NULL);
+
+    /* Start the RTOS Scheduler */
+    vTaskStartScheduler();
+
+    /* HALT */
+    while(1);
+}
+
+
+static void detect_button_press(void *pvParameters)
+{
+    int message_select = 0;
+    struct cw_msg_s msg1 = { "HB9G 1628M",     400, 100 };
+    struct cw_msg_s msg2 = { "HB9G JN36BK",    500, 100 };
+    struct cw_msg_s msg3 = { "HB9G U 12.5 73", 400, 130 };
+
+    GPIO_SetBits(GPIOD, GPIO_Pin_12);
+
+    while (1) {
+        if (GPIO_ReadInputDataBit(GPIOA,GPIO_Pin_0)>0) {
+
+            while (GPIO_ReadInputDataBit(GPIOA,GPIO_Pin_0) > 0) {
+                vTaskDelay(100 / portTICK_RATE_MS); /* Button Debounce Delay */
+            }
+
+            if (message_select == 0) {
+                GPIO_ResetBits(GPIOD, GPIO_Pin_12);
+                GPIO_SetBits(GPIOD, GPIO_Pin_15);
+                cw_push_message(msg1.msg, msg1.dit_duration, msg1.freq);
+                message_select++;
+            }
+            else if (message_select == 1) {
+                GPIO_SetBits(GPIOD, GPIO_Pin_12);
+                cw_push_message(msg2.msg, msg2.dit_duration, msg2.freq);
+                message_select++;
+            }
+            else if (message_select == 2) {
+                GPIO_ResetBits(GPIOD, GPIO_Pin_15);
+                cw_push_message(msg3.msg, msg3.dit_duration, msg3.freq);
+                message_select = 0;
+            }
+
+            while (GPIO_ReadInputDataBit(GPIOA,GPIO_Pin_0) == 0) {
+                vTaskDelay(100 / portTICK_RATE_MS); /* Button Debounce Delay */
+            }
+
+        }
+    }
+}
+
+#define AUDIO_BUF_LEN 4096
+static int16_t audio_buffer0[AUDIO_BUF_LEN];
+static int16_t audio_buffer1[AUDIO_BUF_LEN];
+static void audio_task(void *pvParameters)
+{
+
+    int select_buffer = 0;
+
+    while (1) {
+        int16_t *samples;
+
+        if (select_buffer == 0) {
+            samples = audio_buffer0;
+            GPIO_SetBits(GPIOD, GPIO_Pin_13);
+            GPIO_ResetBits(GPIOD, GPIO_Pin_14);
+            select_buffer = 1;
+        } else {
+            samples = audio_buffer1;
+            GPIO_SetBits(GPIOD, GPIO_Pin_14);
+            GPIO_ResetBits(GPIOD, GPIO_Pin_13);
+            select_buffer = 0;
+        }
+
+        size_t samples_len = cw_fill_buffer(samples, AUDIO_BUF_LEN);
+
+        if (samples_len == 0) {
+            for (int i = 0; i < AUDIO_BUF_LEN; i++) {
+                samples[i] = 0;
+            }
+
+            samples_len = AUDIO_BUF_LEN;
+        }
+
+        ProvideAudioBufferWithoutBlocking(samples, samples_len);
+
+        taskYIELD();
+    }
+}
+
+void init() {
+    GPIO_InitTypeDef  GPIO_InitStructure;
+    USART_InitTypeDef USART_InitStructure;
+    // ---------- SysTick timer -------- //
+    if (SysTick_Config(SystemCoreClock / 1000)) {
+        // Capture error
+        while (1){};
+    }
+
+    // Enable full access to FPU (Should be done automatically in system_stm32f4xx.c):
+    //SCB->CPACR |= ((3UL << 10*2)|(3UL << 11*2));  // set CP10 and CP11 Full Access
+
+    // GPIOD Periph clock enable
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOD, ENABLE);
+
+    // Configure PD12, PD13, PD14 and PD15 in output pushpull mode
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_12 | GPIO_Pin_13| GPIO_Pin_14| GPIO_Pin_15;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_OUT;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_Init(GPIOD, &GPIO_InitStructure);
+
+    // Init PushButton
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_IN;
+    GPIO_InitStructure.GPIO_Pin =  GPIO_Pin_0;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_NOPULL;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_Init(GPIOA, &GPIO_InitStructure);
+
+
+    // ------ UART ------ //
+
+    // Clock
+    RCC_APB1PeriphClockCmd(RCC_APB1Periph_USART2, ENABLE);
+    RCC_AHB1PeriphClockCmd(RCC_AHB1Periph_GPIOA, ENABLE);
+
+    // IO
+    GPIO_InitStructure.GPIO_Pin = GPIO_Pin_5 | GPIO_Pin_6;
+    GPIO_InitStructure.GPIO_Speed = GPIO_Speed_100MHz;
+    GPIO_InitStructure.GPIO_Mode = GPIO_Mode_AF;
+    GPIO_InitStructure.GPIO_OType = GPIO_OType_PP;
+    GPIO_InitStructure.GPIO_PuPd = GPIO_PuPd_UP;
+    GPIO_Init(GPIOD, &GPIO_InitStructure);
+
+    GPIO_PinAFConfig(GPIOD, GPIO_PinSource5, GPIO_AF_USART1);
+    GPIO_PinAFConfig(GPIOD, GPIO_PinSource6, GPIO_AF_USART1);
+
+    // Conf
+    USART_InitStructure.USART_BaudRate = 115200;
+    USART_InitStructure.USART_WordLength = USART_WordLength_8b;
+    USART_InitStructure.USART_StopBits = USART_StopBits_1;
+    USART_InitStructure.USART_Parity = USART_Parity_No;
+    USART_InitStructure.USART_HardwareFlowControl = USART_HardwareFlowControl_None;
+    USART_InitStructure.USART_Mode = USART_Mode_Tx | USART_Mode_Rx;
+    USART_Init(USART2, &USART_InitStructure);
+
+    // Enable
+    USART_Cmd(USART2, ENABLE);
+}
+