twbbif.c File Reference

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Detailed Description

Bit banging two wire interface.

Tested with AT91R40008 only. Other ARMs or AVR may not work.

 *
 * $Log: twbbif.c,v $
 * Revision 1.6  2006/10/08 16:48:09  haraldkipp
 * Documentation fixed
 *
 * Revision 1.5  2006/06/28 17:10:35  haraldkipp
 * Include more general header file for ARM.
 *
 * Revision 1.4  2006/05/25 09:30:23  haraldkipp
 * Compiles for AVR. Still not tested, though.
 *
 * Revision 1.3  2006/04/07 12:50:20  haraldkipp
 * Added additional delays in TwAck.
 * Clock and data forced to high before switching to input gives better
 * waveforms.
 * Additional delay added to set clock to 50% duty cycle. The PCF8563
 * seems to fail, if the clock's high time is much longer than the low time.
 *
 * Revision 1.2  2006/01/23 17:32:35  haraldkipp
 * Automatic initialization added.
 *
 * Revision 1.1  2005/10/24 10:21:57  haraldkipp
 * Initial check in.
 *
 *
 * 

Defines
#define	TWI_DELAY   8
Functions
int	TwMasterTransact (u_char sla, CONST void *txdata, u_short txlen, void *rxdata, u_short rxsiz, u_long tmo)
	Transmit and/or receive data as a master.
int	TwMasterError (void)
	Get last master mode error.
int	TwSlaveListen (u_char *sla, void *rxdata, u_short rxsiz, u_long tmo)
	Listen for incoming data from a master.
int	TwSlaveRespond (void *txdata, u_short txlen, u_long tmo)
	Send response to a master.
int	TwSlaveError (void)
	Get last slave mode error.
int	TwIOCtl (int req, void *conf)
	Perform TWI control functions.
int	TwInit (u_char sla)
	Initialize TWI interface.

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Function Documentation

int TwMasterTransact (  u_char  sla, CONST void *  txdata, u_short  txlen, void *  rxdata, u_short  rxsiz, u_long  tmo )

Transmit and/or receive data as a master. The two-wire serial interface must have been initialized by calling TwInit() before this function can be used. Parameters: sla  Slave address of the destination. This slave address must be specified as a 7-bit address. For example, the PCF8574A may be configured to slave addresses from 0x38 to 0x3F. txdata  Points to the data to transmit. Ignored, if the number of data bytes to transmit is zero. txlen  Number of data bytes to transmit. If zero, then the interface will not send any data to the slave device and will directly enter the master receive mode. rxdata  Points to a buffer, where the received data will be stored. Ignored, if the maximum number of bytes to receive is zero. rxsiz  Maximum number of bytes to receive. Set to zero, if no bytes are expected from the slave device. tmo  Timeout in milliseconds. To disable timeout, set this parameter to NUT_WAIT_INFINITE. Returns: The number of bytes received, -1 in case of an error or timeout. Note: Timeout is not used in the bit banging version.

int TwMasterError (  void   )

Get last master mode error. You may call this function to determine the specific cause of an error after TwMasterTransact() failed. Returns: Error code or 0 if no error occurred.

int TwSlaveListen (  u_char *  sla, void *  rxdata, u_short  rxsiz, u_long  tmo )

Listen for incoming data from a master. If this function returns without error, the bus is blocked. The caller must immediately process the request and return a response by calling TwSlaveRespond(). Note: Slave mode is not implemented in the bit banging version. Thus the function always returns -1. Parameters: sla  Points to a byte variable, which receives the slave address sent by the master. This can be used by the caller to determine whether the the interface has been addressed by a general call or its individual address. rxdata  Points to a data buffer where the received data bytes are stored. rxsiz  Specifies the maximum number of data bytes to receive. tmo  Timeout in milliseconds. To disable timeout, set this parameter to NUT_WAIT_INFINITE. Returns: The number of bytes received, -1 in case of an error or timeout.

int TwSlaveRespond (  void *  txdata, u_short  txlen, u_long  tmo )

Send response to a master. This function must be called as soon as possible after TwSlaveListen() returned successfully, even if no data needs to be returned. Not doing so will completely block the bus. Note: Slave mode is not implemented in the bit banging version. Thus the function always returns -1. Parameters: txdata  Points to the data to transmit. Ignored, if the number of bytes to transmit is zero. txlen  Number of data bytes to transmit. tmo  Timeout in milliseconds. To disable timeout, set this parameter to NUT_WAIT_INFINITE. Returns: The number of bytes transmitted, -1 in case of an error or timeout.

int TwSlaveError (  void   )

Get last slave mode error. You may call this function to determine the specific cause of an error after TwSlaveListen() or TwSlaveRespond() failed. Returns: Error code or 0 if no error occurred. Note: Slave mode is not implemented in the bit banging version. Thus the function always returns TWERR_BUS.

int TwIOCtl (  int  req, void *  conf )

Perform TWI control functions. Not implemented in the bit banging version. Parameters: req  Requested control function. conf  Points to a buffer that contains any data required for the given control function or receives data from that function. Returns: Always 0.

int TwInit (  u_char  sla  )

Initialize TWI interface. The specified slave address is used only, if the local system is running as a slave. Anyway, care must be taken that it doesn't conflict with another connected device. Parameters: sla  Slave address, must be specified as a 7-bit address, always lower than 128. Returns: Always 0. Note: Slave mode is not implemented in the bit banging version. Thus the given slave address is ignored.

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