*
* <b>Low Level API Example:</b>
* \code
- * // Initialise the TWI driver before first use
- * TWI_Init();
+ * // Initialize the TWI driver before first use at 200KHz
+ * TWI_Init(TWI_BIT_PRESCALE_1, TWI_BITLENGTH_FROM_FREQ(1, 200000));
*
* // Start a write session to device at device address 0xA0, internal address 0xDC with a 10ms timeout
- * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_WRITE, 10))
+ * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_WRITE, 10) == TWI_ERROR_NoError)
* {
* TWI_SendByte(0xDC);
*
* }
*
* // Start a read session to device at address 0xA0, internal address 0xDC with a 10ms timeout
- * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_WRITE, 10))
+ * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_WRITE, 10) == TWI_ERROR_NoError)
* {
* TWI_SendByte(0xDC);
* TWI_StopTransmission();
*
- * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_READ, 10))
+ * if (TWI_StartTransmission(0xA0 | TWI_ADDRESS_READ, 10) == TWI_ERROR_NoError)
* {
* uint8_t Byte1, Byte2, Byte3;
*
*
* <b>High Level API Example:</b>
* \code
- * // Initialise the TWI driver before first use
- * TWI_Init();
+ * // Initialize the TWI driver before first use at 200KHz
+ * TWI_Init(TWI_BIT_PRESCALE_1, TWI_BITLENGTH_FROM_FREQ(1, 200000));
*
* // Start a write session to device at device address 0xA0, internal address 0xDC with a 10ms timeout
* uint8_t InternalWriteAddress = 0xDC;
/** TWI slave device address mask for a read session. Mask with a slave device base address to obtain
* the correct TWI bus address for the slave device when reading data from it.
*/
- #define TWI_ADDRESS_READ 0x00
+ #define TWI_ADDRESS_READ 0x01
/** TWI slave device address mask for a write session. Mask with a slave device base address to obtain
* the correct TWI bus address for the slave device when writing data to it.
*/
- #define TWI_ADDRESS_WRITE 0x01
+ #define TWI_ADDRESS_WRITE 0x00
/** Mask to retrieve the base address for a TWI device, which can then be ORed with \ref TWI_ADDRESS_READ
* or \ref TWI_ADDRESS_WRITE to obtain the device's read and write address respectively.
*/
#define TWI_DEVICE_ADDRESS_MASK 0xFE
+ /** Bit length prescaler for \ref TWI_Init(). This mask multiplies the TWI bit length prescaler by 1. */
+ #define TWI_BIT_PRESCALE_1 ((0 << TWPS1) | (0 << TWPS0))
+
+ /** Bit length prescaler for \ref TWI_Init(). This mask multiplies the TWI bit length prescaler by 4. */
+ #define TWI_BIT_PRESCALE_4 ((0 << TWPS1) | (1 << TWPS0))
+
+ /** Bit length prescaler for \ref TWI_Init(). This mask multiplies the TWI bit length prescaler by 16. */
+ #define TWI_BIT_PRESCALE_16 ((1 << TWPS1) | (0 << TWPS0))
+
+ /** Bit length prescaler for \ref TWI_Init(). This mask multiplies the TWI bit length prescaler by 64. */
+ #define TWI_BIT_PRESCALE_64 ((1 << TWPS1) | (1 << TWPS0))
+
+ /** Calculates the length of each bit on the TWI bus for a given target frequency. This may be used with
+ * the \ref TWI_Init() function to convert a bus frequency to a number of clocks for the \c BitLength
+ * parameter.
+ *
+ * \param[in] Prescale Prescaler set on the TWI bus.
+ * \param[in] Frequency Desired TWI bus frequency in Hz.
+ *
+ * \return Bit length in clocks for the given TWI bus frequency at the given prescaler value.
+ */
+ #define TWI_BITLENGTH_FROM_FREQ(Prescale, Frequency) ((((F_CPU / (Prescale)) / (Frequency)) - 16) / 2)
+
/* Enums: */
/** Enum for the possible return codes of the TWI transfer start routine and other dependant TWI functions. */
enum TWI_ErrorCodes_t
{
- TWI_ERROR_NoError = 0, /**< Indicates that the command completed sucessfully. */
+ TWI_ERROR_NoError = 0, /**< Indicates that the command completed successfully. */
TWI_ERROR_BusFault = 1, /**< A TWI bus fault occurred while attempting to capture the bus. */
TWI_ERROR_BusCaptureTimeout = 2, /**< A timeout occurred whilst waiting for the bus to be ready. */
TWI_ERROR_SlaveResponseTimeout = 3, /**< No ACK received at the nominated slave address within the timeout period. */
};
/* Inline Functions: */
- /** Initialises the TWI hardware into master mode, ready for data transmission and reception. This must be
+ /** Initializes the TWI hardware into master mode, ready for data transmission and reception. This must be
* before any other TWI operations.
+ *
+ * The generated SCL frequency will be according to the formula <pre>F_CPU / (16 + 2 * BitLength + 4 ^ Prescale)</pre>.
+ *
+ * \note The value of the \c BitLength parameter should not be set below 10 or invalid bus conditions may
+ * occur, as indicated in the AVR8 microcontroller datasheet.
+ *
+ * \param[in] Prescale Prescaler to use when determining the bus frequency, a \c TWI_BIT_PRESCALE_* value.
+ * \param[in] BitLength Length of the bits sent on the bus.
*/
- static inline void TWI_Init(void) ATTR_ALWAYS_INLINE;
- static inline void TWI_Init(void)
+ static inline void TWI_Init(const uint8_t Prescale, const uint8_t BitLength) ATTR_ALWAYS_INLINE;
+ static inline void TWI_Init(const uint8_t Prescale, const uint8_t BitLength)
{
- TWCR |= (1 << TWEN);
+ TWCR |= (1 << TWEN);
+ TWSR = Prescale;
+ TWBR = BitLength;
}
/** Turns off the TWI driver hardware. If this is called, any further TWI operations will require a call to
TWCR = ((1 << TWINT) | (1 << TWSTO) | (1 << TWEN));
}
- /** Sends a byte to the currently addressed device on the TWI bus.
+ /* Function Prototypes: */
+ /** Begins a master mode TWI bus communication with the given slave device address.
*
- * \param[in] Byte Byte to send to the currently addressed device
+ * \param[in] SlaveAddress Address of the slave TWI device to communicate with.
+ * \param[in] TimeoutMS Timeout period within which the slave must respond, in milliseconds.
*
- * \return Boolean \c true if the recipient ACKed the byte, \c false otherwise
+ * \return A value from the \ref TWI_ErrorCodes_t enum.
*/
- static inline bool TWI_SendByte(const uint8_t Byte)
- {
- TWDR = Byte;
- TWCR = ((1 << TWINT) | (1 << TWEN));
- while (!(TWCR & (1 << TWINT)));
-
- return ((TWSR & TW_STATUS_MASK) == TW_MT_DATA_ACK);
- }
+ uint8_t TWI_StartTransmission(const uint8_t SlaveAddress,
+ const uint8_t TimeoutMS);
- /** Receives a byte from the currently addressed device on the TWI bus.
+ /** Sends a byte to the currently addressed device on the TWI bus.
*
- * \param[in] Byte Location where the read byte is to be stored
- * \param[in] LastByte Indicates if the byte should be ACKed if false, NAKed if true
+ * \param[in] Byte Byte to send to the currently addressed device
*
- * \return Boolean \c true if the byte reception successfully completed, \c false otherwise
+ * \return Boolean \c true if the recipient ACKed the byte, \c false otherwise
*/
- static inline uint8_t TWI_ReceiveByte(uint8_t* const Byte,
- const bool LastByte)
- {
- uint8_t TWCRMask = ((1 << TWINT) | (1 << TWEN));
+ bool TWI_SendByte(const uint8_t Byte);
- if (!(LastByte))
- TWCRMask |= (1 << TWEA);
-
- TWCR = TWCRMask;
- while (!(TWCR & (1 << TWINT)));
- *Byte = TWDR;
-
- return ((TWSR & TW_STATUS_MASK) == TW_MR_DATA_ACK);
- }
-
- /* Function Prototypes: */
- /** Begins a master mode TWI bus communication with the given slave device address.
+ /** Receives a byte from the currently addressed device on the TWI bus.
*
- * \param[in] SlaveAddress Address of the slave TWI device to communicate with
- * \param[in] TimeoutMS Timeout period within which the slave must respond, in milliseconds
+ * \param[in] Byte Location where the read byte is to be stored.
+ * \param[in] LastByte Indicates if the byte should be ACKed if false, NAKed if true.
*
- * \return A value from the \ref TWI_ErrorCodes_t enum
+ * \return Boolean \c true if the byte reception successfully completed, \c false otherwise.
*/
- uint8_t TWI_StartTransmission(const uint8_t SlaveAddress,
- const uint8_t TimeoutMS);
-
+ bool TWI_ReceiveByte(uint8_t* const Byte,
+ const bool LastByte) ATTR_NON_NULL_PTR_ARG(1);
+ bool TWI_ReceiveByte(uint8_t* const Byte,
+ const bool LastByte);
+
/** High level function to perform a complete packet transfer over the TWI bus to the specified
* device.
*
- * \param[in] SlaveAddress Base address of the TWI slave device to communicate with
- * \param[in] TimeoutMS Timeout for bus capture and slave START ACK, in milliseconds
- * \param[in] InternalAddress Pointer to a location where the internal slave read start address is stored
- * \param[in] InternalAddressLen Size of the internal device address, in bytes
- * \param[in] Buffer Pointer to a buffer where the read packet data is to be stored
- * \param[in] Length Size of the packet to read, in bytes
+ * \param[in] SlaveAddress Base address of the TWI slave device to communicate with.
+ * \param[in] TimeoutMS Timeout for bus capture and slave START ACK, in milliseconds.
+ * \param[in] InternalAddress Pointer to a location where the internal slave read start address is stored.
+ * \param[in] InternalAddressLen Size of the internal device address, in bytes.
+ * \param[in] Buffer Pointer to a buffer where the read packet data is to be stored.
+ * \param[in] Length Size of the packet to read, in bytes.
+ *
+ * \return A value from the \ref TWI_ErrorCodes_t enum.
*/
uint8_t TWI_ReadPacket(const uint8_t SlaveAddress,
const uint8_t TimeoutMS,
const uint8_t* InternalAddress,
uint8_t InternalAddressLen,
uint8_t* Buffer,
- uint8_t Length);
+ uint8_t Length) ATTR_NON_NULL_PTR_ARG(3);
/** High level function to perform a complete packet transfer over the TWI bus from the specified
* device.
* \param[in] InternalAddressLen Size of the internal device address, in bytes
* \param[in] Buffer Pointer to a buffer where the packet data to send is stored
* \param[in] Length Size of the packet to send, in bytes
+ *
+ * \return A value from the \ref TWI_ErrorCodes_t enum.
*/
uint8_t TWI_WritePacket(const uint8_t SlaveAddress,
const uint8_t TimeoutMS,
const uint8_t* InternalAddress,
uint8_t InternalAddressLen,
const uint8_t* Buffer,
- uint8_t Length);
+ uint8_t Length) ATTR_NON_NULL_PTR_ARG(3);
/* Disable C linkage for C++ Compilers: */
#if defined(__cplusplus)
projects / pub / lufa.git / blobdiff