Merge io_interfaces repo into helpers

README.md

@@ -32,9 +32,9 @@ Debug serial output macros.
 
 Configuration:
 * `#define STA_DEBUG_SERIAL_ENABLE`: Enable module
-* `#define STA_DEBUG_SERIAL_DISABLE`: Forces module off when defined
-* `DEBUG`: Automatically enables module when defined
-* `NDEBUG`: Forces module off when defined
+* `#define STA_DEBUG_SERIAL_FORCE`: Ignore debug defines and always enable output
+* `DEBUG`: Enables output when defined
+* `NDEBUG`: Disables output when defined (overrides DEBUG)
 
 The `sta::DebugSerial` instance must be provided.
 
@@ -78,4 +78,37 @@ Configuration:
 * `#define STA_HAL_DELAY_US_TIM <tim_handle>`: 1 MHz TIM instance used by `sta::delayUs`
 
 TIM time base must be started before using `sta::delayUs` by calling `sta::initHAL`.
-When using the startup system task this is handled automatically.
+When using the startup system task this is handled automatically.
+
+
+## Interfaces
+
+The intention of these interfaces is to provide an abstraction layer for commonly used
+resources. Libraries using these interfaces can be reused on different platforms
+by simply implementing the required interfaces for the selected platform.
+
+Interfaces for the following resources are provided:
+* GPIO pin
+* Mutex
+* Signal
+* SPI
+* UART
+
+
+## HAL implementations
+
+Implementations using the HAL are provided for the following interfaces:
+* GpioPin
+* SpiInterface, SpiDevice
+* UART
+
+To enable these implementations follow the instructions from the individual headers.
+
+
+## Atomic implementations
+
+Implementations using atomic variables are provided for the following interfaces:
+* Mutex
+* Signal
+
+To enable these implementations define `STA_ATOMIC_ENABLE` in `<sta/config.hpp>`.

include/sta/atomic/mutex.hpp

@@ -0,0 +1,39 @@
+/**
+ * @brief Atomic mutex implementation.
+ *
+ * Configuration:
+ *     STA_ATOMIC_ENABLE: Enable module
+ */
+#ifndef STA_ATOMIC_MUTEX_HPP
+#define STA_ATOMIC_MUTEX_HPP
+
+#include <sta/config.hpp>
+#ifdef STA_ATOMIC_ENABLE
+
+#include <sta/mutex.hpp>
+
+#include <atomic>
+
+
+namespace sta
+{
+	/**
+	 * @brief Implementation of `Mutex` interface using `std::atomic_flag`.
+	 */
+	class AtomicMutex : public Mutex
+	{
+	public:
+		AtomicMutex();
+
+		void acquire() override;
+		void release() override;
+
+	private:
+		std::atomic_flag lock_; /**< Atomic flag used as lock */
+	};
+} // namespace sta
+
+
+#endif // STA_ATOMIC_ENABLE
+
+#endif // STA_ATOMIC_MUTEX_HPP

include/sta/atomic/signal.hpp

@@ -0,0 +1,41 @@
+/**
+ * @brief Atomic signal implementation.
+ *
+ * Configuration:
+ *     STA_ATOMIC_ENABLE: Enable module
+ */
+#ifndef STA_ATOMIC_SIGNAL_HPP
+#define STA_ATOMIC_SIGNAL_HPP
+
+#include <sta/config.hpp>
+#ifdef STA_ATOMIC_ENABLE
+
+#include <sta/signal.hpp>
+
+#include <atomic>
+
+
+namespace sta
+{
+	/**
+	 * @brief Implementation of `Signal` interface using `std::atomic`.
+	 */
+	class AtomicSignal : public Signal
+	{
+	public:
+		AtomicSignal();
+
+		void notify() override;
+		bool peek() override;
+		bool test() override;
+		void wait() override;
+
+	private:
+		std::atomic<bool> signal_;  /**< Atomic bool used as signal */
+	};
+} // namespace sta
+
+
+#endif // STA_ATOMIC_ENABLE
+
+#endif // STA_ATOMIC_SIGNAL_HPP

include/sta/gpio_pin.hpp

@@ -0,0 +1,35 @@
+/**
+ * @brief GPIO pin interface definitions.
+ */
+#ifndef STA_GPIO_PIN_HPP
+#define STA_GPIO_PIN_HPP
+
+
+namespace sta
+{
+	/**
+	 * @brief GPIO pin state
+	 */
+	enum class GpioPinState
+	{
+		LOW,
+		HIGH
+	};
+
+	/**
+	 * @brief Interface for GPIO pins.
+	 */
+	class GpioPin
+	{
+	public:
+		/**
+		 * @brief Set pin output state.
+		 *
+		 * @param state     Output state
+		 */
+		virtual void setState(GpioPinState state) = 0;
+	};
+} // namespace sta
+
+
+#endif // STA_GPIO_PIN_HPP

include/sta/hal/clocks.hpp

@@ -0,0 +1,60 @@
+/**
+ * @brief Helper macros for HAL clock queries.
+ */
+#ifndef STA_HAL_CLOCKS_HPP
+#define STA_HAL_CLOCKS_HPP
+
+#include <sta/config.hpp>
+#include <sta/hal.hpp>
+
+
+/**
+ * @brief Get function returning PCLK frequency.
+ *
+ * @param n Index of peripheral clock
+ */
+#define STA_HAL_GET_PCLK_FREQ_FN(n)             HAL_RCC_GetPCLK ## n ## Freq
+
+
+// Internal helper for macro expansion
+#define _STA_HAL_GET_PCLK_FREQ_FN(n)            STA_HAL_GET_PCLK_FREQ_FN(n)
+// Get instance to PCLK index map macro
+#define _STA_PCLK_IDX_MAP(type, idx)            STA_ ## type ## _ ## idx ## _PCLK_IDX
+// Get HAL handle to PCLK index map macro
+#define _STA_HAL_PCLK_IDX_MAP(handle)           STA_HAL_ ## handle ## _PCLK_IDX
+
+
+/**
+ * @brief Get function returning frequency of PCLK used by TIM.
+ *
+ * @param n         TIM index
+ */
+#define STA_HAL_GET_TIM_PCLK_FREQ_FN(n)         _STA_HAL_GET_PCLK_FREQ_FN(_STA_PCLK_IDX_MAP(TIM, n))
+/**
+ * @brief Get function returning frequency of PCLK used by SPI interface.
+ *
+ * @param n         SPI interface index
+ */
+#define STA_HAL_GET_SPI_PCLK_FREQ_FN(n)         _STA_HAL_GET_PCLK_FREQ_FN(_STA_PCLK_IDX_MAP(SPI, n))
+/**
+ * @brief Get function returning frequency of PCLK used by I2C interface.
+ *
+ * @param n         I2C interface index
+ */
+#define STA_HAL_GET_I2C_PCLK_FREQ_FN(n)         _STA_HAL_GET_PCLK_FREQ_FN(_STA_PCLK_IDX_MAP(I2C, n))
+/**
+ * @brief Get function returning frequency of PCLK used by USART interface.
+ *
+ * @param n         USART interface index
+ */
+#define STA_HAL_GET_USART_PCLK_FREQ_FN(n)       _STA_HAL_GET_PCLK_FREQ_FN(_STA_PCLK_IDX_MAP(USART, n))
+
+/**
+ * @brief Get function returning frequency of PCLK used by HAL instance.
+ *
+ * @param handle    Instance handle
+ */
+#define STA_HAL_GET_HANDLE_PCLK_FREQ_FN(handle) _STA_HAL_GET_PCLK_FREQ_FN(_STA_HAL_PCLK_IDX_MAP(handle))
+
+
+#endif // STA_HAL_CLOCKS_HPP

include/sta/hal/gpio_pin.hpp

@@ -0,0 +1,49 @@
+/**
+ * @brief Wrapper for HAL GPIO pins.
+ *
+ * Configuration:
+ *     STA_HAL_GPIO_ENABLE: Enable module
+ */
+#ifndef STA_HAL_GPIO_PIN_HPP
+#define STA_HAL_GPIO_PIN_HPP
+
+#include <sta/config.hpp>
+#ifdef STA_HAL_GPIO_ENABLE
+
+#include <sta/gpio_pin.hpp>
+#include <sta/hal.hpp>
+
+
+namespace sta
+{
+	/**
+	 * @brief Container for HAL GPIO Pin objects.
+	 */
+	class HalGpioPin : public GpioPin
+	{
+	public:
+		HalGpioPin(GPIO_TypeDef * port, uint16_t pin);
+
+		void setState(GpioPinState state) override;
+
+		GPIO_TypeDef * getPort() const;
+		uint16_t getPin() const;
+		uint8_t getIndex() const;
+
+	private:
+		GPIO_TypeDef * port_;   /**< GPIO port */
+		uint16_t pin_;          /**< GPIO pin */
+	};
+}
+
+/**
+ * @brief Create HalGpioPin object from pin label.
+ *
+ * @param label     Pin label
+ */
+#define STA_HAL_GPIO_PIN(label) sta::HalGpioPin{label##_GPIO_Port, label##_Pin}
+
+
+#endif // STA_HAL_GPIO_ENABLE
+
+#endif // STA_HAL_GPIO_PIN_HPP

include/sta/hal/spi.hpp

@@ -0,0 +1,108 @@
+/**
+ * @brief Implementations for `SpiInterface` and `SpiDevice` using HAL.
+ *
+ * Configuration:
+ *     STA_HAL_SPI_ENABLE: Enable module
+ *
+ * Requires **HAL_GPIO** module.
+ */
+#ifndef STA_HAL_SPI_HPP
+#define STA_HAL_SPI_HPP
+
+#include <sta/config.hpp>
+#ifdef STA_HAL_SPI_ENABLE
+
+#ifndef STA_HAL_GPIO_ENABLE
+#error "HAL GPIO required"
+#endif // !STA_HAL_GPIO_ENABLE
+
+#include <sta/hal.hpp>
+#include <sta/spi_device.hpp>
+#include <sta/hal/clocks.hpp>
+#include <sta/hal/gpio_pin.hpp>
+
+
+namespace sta
+{
+	/**
+	 * @brief Get peripheral clock frequency.
+	 *
+	 * @return Clock frequency
+	 */
+	using HalSpiPCLKFreqFn = uint32_t (*)();
+
+	/**
+	 * @brief Info related to HAL SPI interface.
+	 */
+	struct HalSpiInterfaceInfo
+	{
+		SPI_HandleTypeDef * handle;         /**< Interface handle */
+		HalSpiPCLKFreqFn    getPCLKFreq;    /**< Getter for peripheral clock used by interface */
+	};
+
+
+	/**
+	 * @brief Implementation of `SpiInterface` interface using HAL.
+	 */
+	class HalSpiInterface : public SpiInterface
+	{
+	public:
+		/**
+		 * @param info      SPI interface info
+		 * @param mutex     Mutex object for managing access. Pass nullptr for no access control
+		 */
+		HalSpiInterface(const HalSpiInterfaceInfo & info, Mutex * mutex = nullptr);
+
+		void transfer(uint8_t value) override;
+		void transfer16(uint16_t value) override;
+		void transfer(const uint8_t * buffer, size_t size) override;
+		void transfer(const uint8_t * txBuffer, uint8_t * rxBuffer, size_t size) override;
+		void receive(uint8_t * buffer, size_t size) override;
+
+		void fill(uint8_t value, size_t count) override;
+
+		const SpiSettings & settings() const override;
+
+	private:
+		HalSpiInterfaceInfo info_;  /**< SPI interface info */
+	};
+
+
+	/**
+	 * @brief Implementation of `SpiDevice` interface using HAL.
+	 */
+	class HalSpiDevice : public SpiDevice
+	{
+	public:
+		/**
+		 * @param intf      SPI interface
+		 * @param csPin     Device CS pin
+		 */
+		HalSpiDevice(SpiInterface * intf, HalGpioPin csPin);
+
+		void select() override;
+		void deselect() override;
+
+	private:
+		HalGpioPin csPin_;  /**< Device CS pin */
+	};
+} // namespace sta
+
+
+/**
+ * @brief Get SPI interface info struct for HAL handle.
+ *
+ * Requires STA_HAL_<handle>_PCLK_IDX to be defined for the MCU.
+ * MCU mappings are found in `core` -> sta/mcu/.hpp files.
+ *
+ * Check the MCUs Reference Manual RCC register documentation to see which
+ * peripheral clock is used.
+ *
+ * @param handle    SPI interface handle
+ */
+#define STA_HAL_SPI_INFO(handle) sta::HalSpiInterfaceInfo{&handle, STA_HAL_GET_HANDLE_PCLK_FREQ_FN(handle)}
+
+
+#endif // STA_HAL_SPI_ENABLE
+
+#endif // STA_HAL_SPI_HPP

include/sta/hal/uart.hpp

@@ -0,0 +1,43 @@
+/**
+ * @brief Implementation of UART using HAL.
+ *
+ * Configuration:
+ *     STA_HAL_UART_ENABLE:         Enable module
+ *     STA_HAL_UART_DEBUG_SERIAL:   Create global `sta::DebugSerial` object using this UART instance
+ */
+#ifndef STA_HAL_UART_HPP
+#define STA_HAL_UART_HPP
+
+#include <sta/config.hpp>
+#ifdef STA_HAL_UART_ENABLE
+
+#include <sta/hal.hpp>
+#include <sta/uart.hpp>
+
+
+namespace sta
+{
+	/**
+	 * @brief Implementation of `UART` interface using HAL.
+	 */
+	class HalUART : public UART
+	{
+	public:
+		/**
+		 * @param handle    UART handle
+		 */
+		HalUART(UART_HandleTypeDef * handle);
+
+		using UART::print;
+
+		void write(const uint8_t * buffer, size_t size) override;
+
+	private:
+		UART_HandleTypeDef * handle_;   /**< UART handle */
+	};
+} // namespace sta
+
+
+#endif // STA_HAL_UART_ENABLE
+
+#endif // STA_HAL_UART_HPP

include/sta/mutex.hpp

@@ -0,0 +1,30 @@
+/**
+ * @brief Mutex interface definition.
+ */
+#ifndef STA_MUTEX_HPP
+#define STA_MUTEX_HPP
+
+
+namespace sta
+{
+	/**
+	 * @brief Interface for mutex objects.
+	 */
+	class Mutex
+	{
+	public:
+		/**
+		 * @brief Block until mutex has been acquired
+		 */
+		virtual void acquire() = 0;
+		/**
+		 * @brief Release mutex
+		 */
+		virtual void release() = 0;
+
+		static Mutex * ALWAYS_FREE; /**< Fake mutex that can always be acquired */
+	};
+} // namespace sta
+
+
+#endif // STA_MUTEX_HPP

include/sta/signal.hpp

@@ -0,0 +1,40 @@
+/**
+ * @brief Signal interface definition.
+ */
+#ifndef STA_SIGNAL_HPP
+#define STA_SIGNAL_HPP
+
+
+namespace sta
+{
+	/**
+	 * @brief Interface for signal objects.
+	 */
+	class Signal
+	{
+	public:
+		/**
+		 * @brief Enter signaled state.
+		 */
+		virtual void notify() = 0;
+		/**
+		 * @brief Check signal state w/o changing it.
+		 *
+		 * @return True if in signaled state
+		 */
+		virtual bool peek() = 0;
+		/**
+		 * @brief Check signal state.
+		 *
+		 * @return True if in signaled state
+		 */
+		virtual bool test() = 0;
+		/**
+		 * @brief Wait until signaled state is entered.
+		 */
+		virtual void wait() = 0;
+	};
+} // namespace sta
+
+
+#endif // STA_SIGNAL_HPP

include/sta/spi_device.hpp

@@ -0,0 +1,109 @@
+/**
+ * @brief SPI interface definitions.
+ */
+#ifndef STA_SPI_DEVICE_HPP
+#define STA_SPI_DEVICE_HPP
+
+#include <sta/spi_interface.hpp>
+
+#include <cstdint>
+#include <cstddef>
+
+
+namespace sta
+{
+	/**
+	 * @brief Interface for SPI devices.
+	 */
+	class SpiDevice
+	{
+	public:
+		/**
+		 * @param intf  SPI hardware interface
+		 */
+		SpiDevice(SpiInterface * intf);
+
+
+		/**
+		 * @brief Start transmission with device.
+		 *
+		 * Must be called before any I/O operations.
+		 */
+		void beginTransmission();
+		/**
+		 * @brief End transmission with device.
+		 *
+		 * Must be called after last I/O operation.
+		 */
+		void endTransmission();
+
+
+		/**
+		 * @brief Send single byte of data.
+		 *
+		 * @param value     8-bit value
+		 */
+		void transfer(uint8_t value);
+		/**
+		 * @brief Send two bytes of data.
+		 *
+		 * @param value     16-bit value
+		 */
+		void transfer16(uint16_t data);
+		/**
+		 * @brief Send data from buffer.
+		 *
+		 * @param buffer    Source buffer
+		 * @param size      Number of bytes to transfer
+		 */
+		void transfer(const uint8_t * buffer, size_t size);
+		/**
+		 * @brief Send and receive data simultaneously.
+		 *
+		 * @param txBuffer  Send buffer
+		 * @param rxBuffer  Receive buffer
+		 * @param size      Number of bytes to transfer
+		 */
+		void transfer(const uint8_t * txBuffer, uint8_t * rxBuffer, size_t size);
+		/**
+		 * @brief Read incoming data to buffer.
+		 *
+		 * @param buffer    Destination buffer
+		 * @param size      Number of bytes to read
+		 */
+		void receive(uint8_t * buffer, size_t size);
+
+
+		/**
+		 * @brief Send byte value repeatedly.
+		 *
+		 * @param value     8-bit value to repeat
+		 * @param count     Number of repetitions
+		 */
+		void fill(uint8_t value, size_t count);
+
+
+		/**
+		 * @brief Get SPI interface settings.
+		 *
+		 * @return SPI settings
+		 */
+		const SpiSettings & settings() const;
+
+
+		/**
+		 * @brief Activate device via CS pin.
+		 */
+		virtual void select() = 0;
+		/**
+		 * @brief Deactivate device via CS pin.
+		 */
+		virtual void deselect() = 0;
+
+	private:
+		SpiInterface * intf_;   /**< SPI hardware interface */
+	};
+} // namespace sta
+
+
+#endif // STA_SPI_DEVICE_HPP

include/sta/spi_interface.hpp

@@ -0,0 +1,101 @@
+/**
+ * @brief SPI interface definitions.
+ */
+#ifndef STA_SPI_INTERFACE_HPP
+#define STA_SPI_INTERFACE_HPP
+
+#include <sta/mutex.hpp>
+#include <sta/spi_settings.hpp>
+
+#include <cstdint>
+#include <cstddef>
+
+
+namespace sta
+{
+	/**
+	 * @brief Interface for SPI hardware.
+	 */
+	class SpiInterface
+	{
+	public:
+		/**
+		 * @param settings  SPI interface settings
+		 * @param mutex     Mutex object for managing shared access. Pass nullptr for no access control
+		 */
+		SpiInterface(Mutex * mutex = nullptr);
+
+
+		/**
+		 * @brief Send single byte of data.
+		 *
+		 * @param value     8-bit value
+		 */
+		virtual void transfer(uint8_t value) = 0;
+		/**
+		 * @brief Send two bytes of data.
+		 *
+		 * @param value     16-bit value
+		 */
+		virtual void transfer16(uint16_t value) = 0;
+		/**
+		 * @brief Send data from buffer.
+		 *
+		 * @param buffer    Source buffer
+		 * @param size      Number of bytes to transfer
+		 */
+		virtual void transfer(const uint8_t * buffer, size_t size) = 0;
+		/**
+		 * @brief Send and receive data simultaneously.
+		 *
+		 * @param txBuffer  Send buffer
+		 * @param rxBuffer  Receive buffer
+		 * @param size      Number of bytes to transfer
+		 */
+		virtual void transfer(const uint8_t * txBuffer, uint8_t * rxBuffer, size_t size) = 0;
+		/**
+		 * @brief Read incoming data to buffer.
+		 *
+		 * @param buffer    Destination buffer
+		 * @param size      Number of bytes to read
+		 */
+		virtual void receive(uint8_t * buffer, size_t size) = 0;
+
+
+		/**
+		 * @brief Send byte value repeatedly.
+		 *
+		 * @param value     8-bit value to repeat
+		 * @param count     Number of repetitions
+		 */
+		virtual void fill(uint8_t value, size_t count) = 0;
+
+
+		/**
+		 * @brief Get SPI interface settings.
+		 *
+		 * @return SPI settings
+		 */
+		virtual const SpiSettings & settings() const = 0;
+
+
+		/**
+		 * @brief Acquire usage rights to use the interface.
+		 *
+		 * Must be called before any I/O operations are executed.
+		 */
+		virtual void acquire();
+		/**
+		 * @brief Release usage rights for interface.
+		 *
+		 * Must be called after last I/O operation.
+		 */
+		virtual void release();
+
+	private:
+		Mutex * mutex_;	        /**< Mutex object */
+	};
+} // namespace sta
+
+
+#endif // STA_SPI_INTERFACE_HPP

include/sta/spi_settings.hpp

@@ -0,0 +1,112 @@
+/**
+ * @brief SPI setting types.
+ */
+#ifndef STA_SPI_SETTINGS_HPP
+#define STA_SPI_SETTINGS_HPP
+
+#include <cstdint>
+
+
+namespace sta
+{
+	/**
+	 * @brief SPI clock polarity.
+	 */
+	enum class SpiClkPolarity
+	{
+		LOW,
+		HIGH
+	};
+
+	/**
+	 * @brief SPI clock phase.
+	 */
+	enum class SpiClkPhase
+	{
+		EDGE_1,
+		EDGE_2
+	};
+
+	/**
+	 * @brief SPI clock mode.
+	 */
+	enum class SpiMode
+	{
+		MODE_0,
+		MODE_1,
+		MODE_2,
+		MODE_3
+	};
+
+	/**
+	 * @brief SPI data size.
+	 */
+	enum class SpiDataSize
+	{
+		SIZE_8,
+		SIZE_16
+	};
+
+	/**
+	 * @brief SPI bit order.
+	 */
+	enum class SpiBitOrder
+	{
+		MSB,
+		LSB
+	};
+
+	/**
+	 * @brief Spi baud rate prescaler.
+	 */
+	enum class SpiBaudRatePrescaler
+	{
+		DIV_2,
+		DIV_4,
+		DIV_8,
+		DIV_16,
+		DIV_32,
+		DIV_64,
+		DIV_128,
+		DIV_256
+	};
+
+
+	/**
+	 * @brief SPI settings.
+	 */
+	struct SpiSettings
+	{
+		SpiMode     mode;       /**< SPI clock mode */
+		SpiDataSize dataSize;   /**< SPI data size */
+		SpiBitOrder bitOrder;   /**< SPI bit order */
+		uint32_t    clkSpeed;   /**< SPI clock speed */
+	};
+
+
+	/**
+	 * @brief Get SPI clock polarity from clock mode.
+	 *
+	 * @param mode  SPI clock mode
+	 * @return      SPI clock polarity
+	 */
+	SpiClkPolarity getSpiClkPolarity(SpiMode mode);
+	/**
+	 * @brief Get SPI clock phase from clock mode.
+	 *
+	 * @param mode  SPI clock mode
+	 * @return      SPI clock phase
+	 */
+	SpiClkPhase    getSpiClkPhase(SpiMode mode);
+	/**
+	 * @brief Get SPI clock mode from clock phase and polarity.
+	 *
+	 * @param polarity  SPI clock polarity
+	 * @param phase     SPI clock phase
+	 * @return          SPI clock mode
+	 */
+	SpiMode        getSpiMode(SpiClkPolarity polarity, SpiClkPhase phase);
+} // namespace sta
+
+
+#endif // STA_SPI_SETTINGS_HPP

include/sta/uart.hpp

@@ -0,0 +1,198 @@
+/**
+ * @brief UART interface definition.
+ */
+#ifndef STA_UART_HPP
+#define STA_UART_HPP
+
+#include <cstddef>
+#include <cstdint>
+
+
+namespace sta
+{
+	/**
+	 * @brief Integer representation.
+	 */
+	enum class IntegerBase
+	{
+		DEC,    /**< Decimal */
+		BIN,    /**< Binary */
+		HEX     /**< Hexadecimal */
+	};
+
+	/**
+	 * @brief Interface for UART.
+	 */
+	class UART
+	{
+	public:
+		/**
+		 * @brief Print single character.
+		 *
+		 * @param c     Character to print
+		 */
+		void print(char c);
+		/**
+		 * @brief Print boolean value.
+		 *
+		 * @param b     Boolean value
+		 */
+		void print(bool b);
+		/**
+		 * @brief Print floating point value.
+		 *
+		 * @param d     Floating point value
+		 */
+		void print(double d);
+		/**
+		 * @brief Print integer in selected base.
+		 *
+		 * @param num   8-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void print(uint8_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base.
+		 *
+		 * @param num   16-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void print(uint16_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base.
+		 *
+		 * @param num   32-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void print(uint32_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base.
+		 *
+		 * @param num   Integer
+		 * @param base  Integer base
+		 */
+		void print(size_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print c-string.
+		 *
+		 * @param str   Null terminated string
+		 */
+		void print(const char * str);
+		/**
+		 * @brief Print string.
+		 *
+		 * @param str       String buffer
+		 * @parma length    String length
+		 */
+		void print(const char * str, size_t length);
+
+
+		/**
+		 * @brief Print new-line.
+		 */
+		void println();
+		/**
+		 * @brief Print single character followed by a new-line.
+		 *
+		 * @param c     Character to print
+		 */
+		void println(char c);
+		/**
+		 * @brief Print boolean value followed by a new-line.
+		 *
+		 * @param b     Boolean value
+		 */
+		void println(bool b);
+		/**
+		 * @brief Print floating point value followed by a new-line.
+		 *
+		 * @param d     Floating point value
+		 */
+		void println(double d);
+		/**
+		 * @brief Print integer in selected base followed by a new-line.
+		 *
+		 * @param num   8-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void println(uint8_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base followed by a new-line.
+		 *
+		 * @param num   16-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void println(uint16_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base followed by a new-line.
+		 *
+		 * @param num   32-bit unsigned integer
+		 * @param base  Integer base
+		 */
+		void println(uint32_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print integer in selected base followed by a new-line.
+		 *
+		 * @param num   Integer
+		 * @param base  Integer base
+		 */
+		void println(size_t num, IntegerBase base = IntegerBase::DEC);
+		/**
+		 * @brief Print c-string followed by a new-line.
+		 *
+		 * @param str   Null terminated string
+		 */
+		void println(const char * str);
+		/**
+		 * @brief Print string followed by a new-line.
+		 *
+		 * @param str       String buffer
+		 * @parma length    String length
+		 */
+		void println(const char * str, size_t length);
+
+
+		/**
+		 * @brief Write buffer to UART.
+		 *
+		 * @param buffer    Source buffer
+		 * @param size      Number of bytes in buffer
+		 */
+		virtual void write(const uint8_t * buffer, size_t size) = 0;
+
+	private:
+		/**
+		 * @brief Print unsigned integer in selected base.
+		 *
+		 * @param value     Unsigned integer value
+		 * @param base      Integer base
+		 * @param fmt       printf format string for base 10
+		 * @param size      Size of value in bytes
+		 */
+		void printBase(uintmax_t value, IntegerBase base, const char * fmt, size_t size);
+		/**
+		 * @brief Print unsigned integer in base 10.
+		 *
+		 * @param value     Unsigned integer value
+		 * @param fmt       printf format string
+		 */
+		void printDec(uintmax_t value, const char * fmt);
+		/**
+		 * @brief Print unsigned integer in base 2.
+		 *
+		 * @param value     Unsigned integer value
+		 * @param digits    Number of digits to print
+		 */
+		void printBin(uintmax_t value, size_t digits);
+		/**
+		 * @brief Print unsigned integer in base 16.
+		 *
+		 * @param value     Unsigned integer value
+		 * @param digits    Number of digits to print
+		 */
+		void printHex(uintmax_t value, size_t digits);
+	};
+} // namespace sta
+
+
+#endif // STA_UART_HPP

src/atomic/mutex.cpp

@@ -0,0 +1,23 @@
+#include <sta/atomic/mutex.hpp>
+#ifdef STA_ATOMIC_ENABLE
+
+
+namespace sta
+{
+	AtomicMutex::AtomicMutex()
+		: lock_{ATOMIC_FLAG_INIT}
+	{}
+
+	void AtomicMutex::acquire()
+	{
+		while (lock_.test_and_set());
+	}
+
+	void AtomicMutex::release()
+	{
+		lock_.clear();
+	}
+} // namespace sta
+
+
+#endif // STA_ATOMIC_ENABLE

src/atomic/signal.cpp

@@ -0,0 +1,33 @@
+#include <sta/atomic/signal.hpp>
+#ifdef STA_ATOMIC_ENABLE
+
+
+namespace sta
+{
+	AtomicSignal::AtomicSignal()
+		: signal_{false}
+	{}
+
+	void AtomicSignal::notify()
+	{
+		signal_.store(true);
+	}
+
+	bool AtomicSignal::peek()
+	{
+		return signal_.load();
+	}
+
+	bool AtomicSignal::test()
+	{
+		return signal_.exchange(false);
+	}
+
+	void AtomicSignal::wait()
+	{
+		while (!signal_.exchange(false));
+	}
+} // namespace sta
+
+
+#endif // STA_ATOMIC_ENABLE

src/hal/gpio_pin.cpp

@@ -0,0 +1,38 @@
+#include <sta/hal/gpio_pin.hpp>
+
+#ifdef STA_HAL_GPIO_ENABLE
+
+#include <sta/assert.hpp>
+
+
+namespace sta
+{
+	HalGpioPin::HalGpioPin(GPIO_TypeDef * port, uint16_t pin)
+		: port_{port}, pin_{pin}
+	{
+		STA_ASSERT(port != nullptr);
+	}
+
+	void HalGpioPin::setState(GpioPinState state)
+	{
+		HAL_GPIO_WritePin(port_, pin_, (state == GpioPinState::LOW) ? GPIO_PIN_RESET : GPIO_PIN_SET);
+	}
+
+	GPIO_TypeDef * HalGpioPin::getPort() const
+	{
+		return port_;
+	}
+
+	uint16_t HalGpioPin::getPin() const
+	{
+		return pin_;
+	}
+
+	uint8_t HalGpioPin::getIndex() const
+	{
+		return GPIO_GET_INDEX(port_);
+	}
+} // namespace sta
+
+
+#endif // STA_HAL_GPIO_ENABLE

src/hal/spi.cpp

@@ -0,0 +1,194 @@
+#include <sta/hal/spi.hpp>
+
+#ifdef STA_HAL_SPI_ENABLE
+
+#include <sta/assert.hpp>
+#include <sta/endian.hpp>
+#include <sta/lang.hpp>
+
+
+#ifdef STA_MCU_LITTLE_ENDIAN
+#  define STA_HAL_SPI_REVERSE_BIT_ORDER SpiBitOrder::MSB
+#elif STA_MCU_BIG_ENDIAN
+#  define STA_HAL_SPI_REVERSE_BIT_ORDER SpiBitOrder::LSB
+#else // !STA_MCU_LITTLE_ENDIAN && !STA_MCU_BIG_ENDIAN
+#  ifdef STA_HAL_SPI_REVERSE_BIT_ORDER
+#    warning "Internal STA_HAL_SPI_REVERSE_BIT_ORDER macro manually defined! Better now what you are doing!!!"
+#  else // !STA_HAL_SPI_REVERSE_BIT_ORDER
+#    error "Unknown endian-ness. Define STA_MCU_LITTLE_ENDIAN or STA_MCU_BIG_ENDIAN in <sta/config.hpp>"
+# endif // !STA_HAL_SPI_REVERSE_BIT_ORDER
+#endif // !STA_MCU_LITTLE_ENDIAN && !STA_MCU_BIG_ENDIAN
+
+
+namespace sta
+{
+	static SpiSettings getHalSpiSettings(SPI_HandleTypeDef * handle, uint32_t pclkFreq)
+	{
+		SpiSettings settings;
+
+		settings.mode        = getSpiMode(
+			(handle->Init.CLKPolarity == SPI_POLARITY_LOW) ? SpiClkPolarity::LOW : SpiClkPolarity::HIGH,
+			(handle->Init.CLKPhase == SPI_PHASE_1EDGE) ? SpiClkPhase::EDGE_1 : SpiClkPhase::EDGE_2
+		);
+		settings.dataSize    = (handle->Init.DataSize == SPI_DATASIZE_8BIT) ? SpiDataSize::SIZE_8 : SpiDataSize::SIZE_16;
+		settings.bitOrder    = (handle->Init.FirstBit == SPI_FIRSTBIT_MSB) ? SpiBitOrder::MSB : SpiBitOrder::LSB;
+
+		uint32_t prescaler = 1;
+		switch (handle->Init.BaudRatePrescaler)
+		{
+		case SPI_BAUDRATEPRESCALER_2:
+			prescaler = 2;
+			break;
+		case SPI_BAUDRATEPRESCALER_4:
+			prescaler = 4;
+			break;
+		case SPI_BAUDRATEPRESCALER_8:
+			prescaler = 8;
+			break;
+		case SPI_BAUDRATEPRESCALER_16:
+			prescaler = 16;
+			break;
+		case SPI_BAUDRATEPRESCALER_32:
+			prescaler = 32;
+			break;
+		case SPI_BAUDRATEPRESCALER_64:
+			prescaler = 64;
+			break;
+		case SPI_BAUDRATEPRESCALER_128:
+			prescaler = 128;
+			break;
+		case SPI_BAUDRATEPRESCALER_256:
+			prescaler = 256;
+			break;
+		default:
+			// Unreachable case
+			STA_ASSERT_MSG(false, "Case for SPI_BAUDRATEPRESCALER not handled");
+			STA_UNREACHABLE();
+		}
+
+		// SPI clock speed is based of PCLK
+		settings.clkSpeed = pclkFreq / prescaler;
+
+		return settings;
+	}
+
+
+	HalSpiInterface::HalSpiInterface(const HalSpiInterfaceInfo & info, Mutex * mutex /* = nullptr */)
+		: SpiInterface(mutex), info_{info}
+	{
+		STA_ASSERT(info.handle != nullptr);
+		STA_ASSERT(info.getPCLKFreq != nullptr);
+	}
+
+
+	void HalSpiInterface::transfer(uint8_t value)
+	{
+		if (settings().dataSize == SpiDataSize::SIZE_8)
+		{
+			HAL_SPI_Transmit(info_.handle, &value, 1, HAL_MAX_DELAY);
+		}
+		else
+		{
+			// Required since tx buffer is cast to uint16_t * internally
+			uint16_t dummy = value;
+			HAL_SPI_Transmit(info_.handle, reinterpret_cast<uint8_t *>(&dummy), 1, HAL_MAX_DELAY);
+		}
+	}
+
+	void HalSpiInterface::transfer16(uint16_t value)
+	{
+		static_assert(sizeof(value) == 2, "Unexpected uint16_t size");
+
+		uint16_t size = 1;
+
+		// Send as two bytes if data size is 8-bit
+		if (settings().dataSize == SpiDataSize::SIZE_8)
+		{
+			size = 2;
+
+			if (settings().bitOrder == STA_HAL_SPI_REVERSE_BIT_ORDER)
+			{
+				// Reverse byte order from internal representation
+				value = STA_UINT16_SWAP_BYTE_ORDER(value);
+			}
+		}
+
+		HAL_SPI_Transmit(info_.handle, reinterpret_cast<uint8_t *>(&value), size, HAL_MAX_DELAY);
+	}
+
+	void HalSpiInterface::transfer(const uint8_t * buffer, size_t size)
+	{
+		STA_ASSERT(buffer != nullptr);
+		STA_ASSERT(size != 0);
+
+		HAL_SPI_Transmit(info_.handle, const_cast<uint8_t *>(buffer), size, HAL_MAX_DELAY);
+	}
+
+	void HalSpiInterface::transfer(const uint8_t * txBuffer, uint8_t * rxBuffer, size_t size)
+	{
+		STA_ASSERT(txBuffer != nullptr);
+		STA_ASSERT(rxBuffer != nullptr);
+		STA_ASSERT(size != 0);
+
+		HAL_SPI_TransmitReceive(info_.handle, const_cast<uint8_t *>(txBuffer), rxBuffer, size, HAL_MAX_DELAY);
+	}
+
+	void HalSpiInterface::receive(uint8_t * buffer, size_t size)
+	{
+		STA_ASSERT(buffer != nullptr);
+
+		HAL_SPI_Receive(info_.handle, buffer, size, HAL_MAX_DELAY);
+	}
+
+
+	void HalSpiInterface::fill(uint8_t value, size_t count)
+	{
+		STA_ASSERT(count != 0);
+
+		if (settings().dataSize == SpiDataSize::SIZE_8)
+		{
+			for (size_t i = 0; i < count; ++i)
+			{
+				HAL_SPI_Transmit(info_.handle, &value, 1, HAL_MAX_DELAY);
+			}
+		}
+		else
+		{
+			// Required since tx buffer is cast to uint16_t * internally
+			uint16_t dummy = value;
+			for (size_t i = 0; i < count; ++i)
+			{
+				HAL_SPI_Transmit(info_.handle, reinterpret_cast<uint8_t *>(&dummy), 1, HAL_MAX_DELAY);
+			}
+		}
+	}
+
+
+	const SpiSettings & HalSpiInterface::settings() const
+	{
+		// Cache settings
+		static SpiSettings settings = getHalSpiSettings(info_.handle, info_.getPCLKFreq());
+
+		return settings;
+	}
+
+
+
+
+	HalSpiDevice::HalSpiDevice(SpiInterface * intf, HalGpioPin csPin)
+		: SpiDevice(intf), csPin_{csPin}
+	{}
+
+	void HalSpiDevice::select()
+	{
+		csPin_.setState(GpioPinState::LOW);
+	}
+
+	void HalSpiDevice::deselect()
+	{
+		csPin_.setState(GpioPinState::HIGH);
+	}
+} // namespace sta
+
+
+#endif // STA_HAL_SPI_ENABLE

src/hal/uart.cpp

@@ -0,0 +1,44 @@
+#include <sta/hal/uart.hpp>
+
+#ifdef STA_HAL_UART_ENABLE
+
+#include <sta/assert.hpp>
+
+
+namespace sta
+{
+	HalUART::HalUART(UART_HandleTypeDef * handle)
+		: handle_{handle}
+	{
+		STA_ASSERT(handle != nullptr);
+	}
+
+
+	void HalUART::write(const uint8_t * buffer, size_t size)
+	{
+		STA_ASSERT(buffer != nullptr);
+
+		HAL_UART_Transmit(handle_, const_cast<uint8_t *>(buffer), size, HAL_MAX_DELAY);
+	}
+} // namespace sta
+
+
+#ifdef STA_HAL_UART_DEBUG_SERIAL
+
+// Get extern declaration for DebugSerial because const namespace level variables have internal linkage by default
+#include <sta/debug_serial.hpp>
+
+#include <usart.h>
+
+namespace sta
+{
+	HalUART gHalDebugSerial(&STA_HAL_UART_DEBUG_SERIAL);
+
+	// Used by <sta/debug.hpp>
+	UART * const DebugSerial = &gHalDebugSerial;
+} // namespace sta
+
+#endif // STA_HAL_UART_DEBUG_SERIAL
+
+
+#endif // STA_HAL_UART_ENABLE

src/mutex.cpp

@@ -0,0 +1,20 @@
+#include <sta/mutex.hpp>
+
+
+namespace sta
+{
+	/**
+	 * @brief Dummy mutex implementation with no access control.
+	 */
+	class DummyMutex : public Mutex
+	{
+	public:
+		void acquire() override {}
+		void release() override {}
+	};
+
+	static DummyMutex dummyMutex;
+
+
+	Mutex * Mutex::ALWAYS_FREE = &dummyMutex;
+} // namespace sta

src/spi_device.cpp

@@ -0,0 +1,76 @@
+#include <sta/spi_device.hpp>
+
+#include <sta/assert.hpp>
+
+
+namespace sta
+{
+	SpiDevice::SpiDevice(SpiInterface * intf)
+		: intf_{intf}
+	{
+		STA_ASSERT(intf != nullptr);
+	}
+
+	void SpiDevice::beginTransmission()
+	{
+		// Acquire SPI access and activate device
+		intf_->acquire();
+		select();
+	}
+
+	void SpiDevice::endTransmission()
+	{
+		// Deactivate device and release SPI access
+		deselect();
+		intf_->release();
+	}
+
+
+	// Forward I/O operations to SPI interface
+
+	void SpiDevice::transfer(uint8_t data)
+	{
+		intf_->transfer(data);
+	}
+
+	void SpiDevice::transfer16(uint16_t data)
+	{
+		intf_->transfer16(data);
+	}
+
+	void SpiDevice::transfer(const uint8_t * buffer, size_t size)
+	{
+		STA_ASSERT(buffer != nullptr);
+
+		intf_->transfer(buffer, size);
+	}
+
+	void SpiDevice::transfer(const uint8_t * txBuffer, uint8_t * rxBuffer, size_t size)
+	{
+		STA_ASSERT(txBuffer != nullptr);
+		STA_ASSERT(rxBuffer != nullptr);
+		STA_ASSERT(size != 0);
+
+		intf_->transfer(txBuffer, rxBuffer, size);
+	}
+
+	void SpiDevice::receive(uint8_t * buffer, size_t size)
+	{
+		STA_ASSERT(buffer != nullptr);
+
+		intf_->receive(buffer, size);
+	}
+
+	void SpiDevice::fill(uint8_t value, size_t count)
+	{
+		STA_ASSERT(count != 0);
+
+		intf_->fill(value, count);
+	}
+
+
+	const SpiSettings & SpiDevice::settings() const
+	{
+		return intf_->settings();
+	}
+} // namespace sta

src/spi_interface.cpp

@@ -0,0 +1,21 @@
+#include <sta/spi_interface.hpp>
+
+
+namespace sta
+{
+	SpiInterface::SpiInterface(Mutex * mutex /* = nullptr */)
+		: mutex_{mutex}
+	{}
+
+	void SpiInterface::acquire()
+	{
+		if (mutex_ != nullptr)
+			mutex_->acquire();
+	}
+
+	void SpiInterface::release()
+	{
+		if (mutex_ != nullptr)
+			mutex_->release();
+	}
+} // namespace sta

src/spi_settings.cpp

@@ -0,0 +1,72 @@
+#include <sta/spi_settings.hpp>
+
+#include <sta/assert.hpp>
+#include <sta/lang.hpp>
+
+
+namespace sta
+{
+	SpiClkPolarity getSpiClkPolarity(SpiMode mode)
+	{
+		switch (mode)
+		{
+		case SpiMode::MODE_0:
+		case SpiMode::MODE_1:
+			return SpiClkPolarity::LOW;
+
+		case SpiMode::MODE_2:
+		case SpiMode::MODE_3:
+			return SpiClkPolarity::HIGH;
+
+		default:
+			// Unreachable case
+			STA_ASSERT_MSG(false, "Case for SpiMode enum not handled");
+			STA_UNREACHABLE();
+		}
+	}
+
+	SpiClkPhase getSpiClkPhase(SpiMode mode)
+	{
+		switch (mode)
+		{
+		case SpiMode::MODE_0:
+		case SpiMode::MODE_2:
+			return SpiClkPhase::EDGE_1;
+
+		case SpiMode::MODE_1:
+		case SpiMode::MODE_3:
+			return SpiClkPhase::EDGE_2;
+
+		default:
+			// Unreachable case
+			STA_ASSERT_MSG(false, "Case for SpiMode enum not handled");
+			STA_UNREACHABLE();
+		}
+	}
+
+	SpiMode getSpiMode(SpiClkPolarity polarity, SpiClkPhase phase)
+	{
+		if (polarity == SpiClkPolarity::LOW)
+		{
+			if (phase == SpiClkPhase::EDGE_1)
+			{
+				return SpiMode::MODE_0;
+			}
+			else
+			{
+				return SpiMode::MODE_1;
+			}
+		}
+		else
+		{
+			if (phase == SpiClkPhase::EDGE_1)
+			{
+				return SpiMode::MODE_2;
+			}
+			else
+			{
+				return SpiMode::MODE_3;
+			}
+		}
+	}
+} // namespace sta

src/uart.cpp

@@ -0,0 +1,203 @@
+#include <sta/uart.hpp>
+
+#include <sta/printf.hpp>
+
+#include <cstring>
+#include <cinttypes>
+
+
+
+namespace sta
+{
+	void UART::print(char c)
+	{
+		print(&c, 1);
+	}
+
+	void UART::print(bool b)
+	{
+		print(b ? "true" : "false");
+	}
+
+	void UART::print(double d)
+	{
+		char buffer[64];
+		snprintf(buffer, sizeof(buffer), "%f", d);
+		print(buffer);
+	}
+
+	void UART::print(uint8_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		printBase(num, base, "%" PRIu8, sizeof(num));
+	}
+
+	void UART::print(uint16_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		printBase(num, base, "%" PRIu16, sizeof(num));
+	}
+
+	void UART::print(uint32_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		printBase(num, base, "%" PRIu32, sizeof(num));
+	}
+
+	void UART::print(size_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		printBase(num, base, "%z", sizeof(num));
+	}
+
+	void UART::print(const char * str)
+	{
+		print(str, strlen(str));
+	}
+
+	void UART::print(const char * str, size_t length)
+	{
+		write(reinterpret_cast<const uint8_t *>(str), length);
+	}
+
+
+	void UART::println()
+	{
+		print("\r\n", 2);
+	}
+
+	void UART::println(char c)
+	{
+		print(&c, 1);
+		println();
+	}
+
+	void UART::println(bool b)
+	{
+		print(b);
+		println();
+	}
+
+	void UART::println(double d)
+	{
+		print(d);
+		println();
+	}
+
+	void UART::println(uint8_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		print(num, base);
+		println();
+	}
+
+	void UART::println(uint16_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		print(num, base);
+		println();
+	}
+
+	void UART::println(uint32_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		print(num, base);
+		println();
+	}
+
+	void UART::println(size_t num, IntegerBase base /* = IntegerBase::DEC */)
+	{
+		print(num, base);
+		println();
+	}
+
+	void UART::println(const char * str)
+	{
+		println(str, strlen(str));
+	}
+
+	void UART::println(const char * str, size_t length)
+	{
+		print(str, length);
+		println();
+	}
+
+
+
+	void UART::printBase(uintmax_t num, IntegerBase base, const char * fmt, size_t size)
+	{
+		switch (base)
+		{
+		case IntegerBase::DEC:
+			printDec(num, fmt);
+			break;
+
+		case IntegerBase::BIN:
+			// Digits in base 2 = size in bytes * 8
+			printBin(num, size * 8);
+			break;
+
+		case IntegerBase::HEX:
+			// Digits in base 16 = size in bytes * 2
+			printHex(num, size * 2);
+			break;
+
+		default:
+			print("<invalid_base>");
+		}
+	}
+
+	void UART::printDec(uintmax_t num, const char * fmt)
+	{
+		char buffer[64];
+		snprintf(buffer, sizeof(buffer), fmt, static_cast<uint32_t>(num));
+		print(buffer);
+	}
+
+	void UART::printBin(uintmax_t value, size_t digits)
+	{
+		// Need 8 digits for every byte
+		char buffer[sizeof(value) * 8];
+
+		// Check bounds
+		if (digits > sizeof(buffer))
+		{
+			print("<bin_value_too_big>");
+			return;
+		}
+		// Nothing to do
+		if (digits == 0)
+			return;
+
+		for (size_t i = 0; i < digits; ++i)
+		{
+			// Convert bit to '0' or '1'
+			// First digit in buffer is MSB in value, so shift from high to low
+			buffer[i] = '0' + ((value >> (digits - 1 - i)) & 0x1);
+		}
+
+		print(buffer, digits);
+	}
+
+	void UART::printHex(uintmax_t value, size_t digits)
+	{
+		// Need 2 digits for every byte
+		char buffer[sizeof(value) * 2];
+
+		// Check bounds
+		if (digits > sizeof(buffer))
+		{
+			print("<hex_value_too_big>");
+			return;
+		}
+		// Nothing to do
+		if (digits == 0)
+			return;
+
+		for (size_t i = 0; i < digits; ++i)
+		{
+			// Convert 4 bits to hex
+			// First digit in buffer is 4 MSBs in value, so shift from high to low
+			uint8_t hex = ((value >> ((digits - 1 - i) * 4)) & 0xF);
+			if (hex > 9)
+				buffer[i] = 'A' + (hex - 10);
+			else
+				buffer[i] = '0' + hex;
+		}
+
+		print(buffer, digits);
+	}
+} // namespace sta