From 66c38cd940714287e4e11729bf688211902b464d Mon Sep 17 00:00:00 2001 From: Dean Camera Date: Sat, 26 Feb 2011 15:57:06 +0000 Subject: Added TWI baud rate prescaler and bit length parameters to the TWI_Init() function (thanks to Thomas Herlinghaus). --- LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h | 32 +++++++++++++++++++++++++++----- 1 file changed, 27 insertions(+), 5 deletions(-) (limited to 'LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h') diff --git a/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h b/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h index e03423385..feac8a858 100644 --- a/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h +++ b/LUFA/Drivers/Peripheral/AVR8/TWI_AVR8.h @@ -53,7 +53,7 @@ * Low Level API Example: * \code * // Initialise the TWI driver before first use - * TWI_Init(); + * TWI_Init(TWI_BIT_PRESCALE_1, 10); * * // 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)) @@ -92,7 +92,7 @@ * High Level API Example: * \code * // Initialise the TWI driver before first use - * TWI_Init(); + * TWI_Init(TWI_BIT_PRESCALE_1, 10); * * // Start a write session to device at device address 0xA0, internal address 0xDC with a 10ms timeout * uint8_t InternalWriteAddress = 0xDC; @@ -155,6 +155,18 @@ */ #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)) + /* Enums: */ /** Enum for the possible return codes of the TWI transfer start routine and other dependant TWI functions. */ enum TWI_ErrorCodes_t @@ -170,11 +182,21 @@ /* Inline Functions: */ /** Initialises 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 
F_CPU / (16 + 2 * BitLength + 4 ^ Prescale)
. + * + * \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 -- cgit v1.2.3