hsk_ssc.h File Reference

HSK Synchronous Serial Interface headers. More...

#include "hsk_ssc.isr"

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Macros
#define	SSC_MRST_P05   1
	Master mode RX, slave mode TX port P0.5. More...
#define	SSC_MRST_P14   0
	Master mode RX, slave mode TX port P1.4. More...
#define	SSC_MRST_P15   2
	Master mode RX, slave mode TX port P1.5. More...
#define	SSC_MTSR_P04   (1 << 2)
	Master mode TX, slave mode RX port P0.4. More...
#define	SSC_MTSR_P13   (0 << 2)
	Master mode TX, slave mode RX port P1.3. More...
#define	SSC_MTSR_P14   (2 << 2)
	Master mode TX, slave mode RX port P1.4. More...
#define	SSC_SCLK_P03   (1 << 4)
	Synchronous clock port P0.3. More...
#define	SSC_SCLK_P12   (0 << 4)
	Synchronous clock port P1.2. More...
#define	SSC_SCLK_P13   (2 << 4)
	Synchronous clock port P1.3. More...
#define	SSC_MASTER   1
	Master mode, output shift clock on SCLK. More...
#define	SSC_SLAVE   0
	Slave mode, receive shift clock on SCLK. More...
#define	SSC_BAUD(bps)   (uword)(12000000ul / (bps) - 1)
	Converts a baud rate value in bits/s into a baud rate value for the hsk_ssc_init() function. More...
#define	SSC_CONF(width, heading, phase, polarity, duplex)   (((width) - 1) | ((heading) << 4) | ((phase) << 5) | ((polarity) << 6) | ((duplex) << 7))
	Generates an SSC configuration byte. More...
#define	hsk_ssc_busy()   ESSC
	Returns whether the SSC is currently busy with data transmission. More...

Functions
void	hsk_ssc_init (const uword baud, const ubyte config, const bool mode)
	The maximum baud rate in master mode is 12000000 bits/s, and 6000000 bits/s in slave mode. More...
void	hsk_ssc_ports (const ubyte ports)
	Configure the I/O ports of the SSC unit. More...
void	hsk_ssc_talk (char *buffer, ubyte len)
	Send and receive data. More...
void	hsk_ssc_enable ()
	Turn the SSC module on. More...
void	hsk_ssc_disable ()
	Turn the SSC module off. More...

Detailed Description

HSK Synchronous Serial Interface headers.

General purpose serial communication, setup in the following order:

• hsk_ssc_init()
• hsk_ssc_ports()
• hsk_ssc_enable()

Communication is established by the hsk_ssc_talk() function. Use hsk_ssc_busy() to detect whether a buffer was completely read and written.

Author

kami

Half Duplex Operation

For half duplex operation TX and RX pins need to be short circuited.

The TX pin is set up in open drain mode, i.e. an external pull-up resistor is required.

The TX pin needs to be manually configured before calling hsk_ssc_talk() in order to speak or listen on the bus. To listen the TX pin needs to be configured as an input pin, to speak on the bus as an output pin. For efficiency reasons this is not handled by this library (it would result in lots of runtime logic for what should be a single instruction).

Instead it is recommended to define macros in a central header. E.g. for the port configuration SSC_MRST_P05 in slave mode the following code would work:

#define SSC_TX()        (P0_DIR |= 1 << 5)
#define SSC_RX()        (P0_DIR &= ~(1 << 5))

Syntactically it can be used like a regular function:

SSC_TX();
hsk_ssc_talk(buffer, sizeof(buffer) - 1);

Macro Definition Documentation

#define hsk_ssc_busy

(

)

ESSC

Returns whether the SSC is currently busy with data transmission.

#define SSC_BAUD

(

bps

)

(uword)(12000000ul / (bps) - 1)

Converts a baud rate value in bits/s into a baud rate value for the hsk_ssc_init() function.

The distance between adjustable baud rates grows exponentially. Available baud rates in kBit progress like this:

Use the following formula to determine the baud rate that results from a desired value:

Note

The maximum speed is 12 Mbit/s in master mode and 6 Mbit/s in slave mode.

Parameters

bps	The desired number in bits/s

Returns

A timer reload value

#define SSC_CONF	(		width,
			heading,
			phase,
			polarity,
			duplex
	)		(((width) - 1) | ((heading) << 4) | ((phase) << 5) | ((polarity) << 6) | ((duplex) << 7))

Generates an SSC configuration byte.

For details check the XC878 user manual section 12.3.5.1.

Parameters

width	The data with in bits, the available range is
heading	Use 0 for transmitting/receiving LSB first, 1 for MSB first
phase	Use 0 to shift on leading and latch on trailing edge, use 1 to shift on trailing and latch on leading edge
polarity	Use 0 for low idle clock, and 1 for high idle clock
duplex	Use 0 for full duplex mode and 1 for half duplex

#define SSC_MASTER   1

Master mode, output shift clock on SCLK.

#define SSC_SLAVE   0

Slave mode, receive shift clock on SCLK.

Function Documentation

void hsk_ssc_disable

(

)

Turn the SSC module off.

void hsk_ssc_enable

(

)

Turn the SSC module on.

void hsk_ssc_init	(	const uword	baud,
		const ubyte	config,
		const bool	mode
	)

The maximum baud rate in master mode is 12000000 bits/s, and 6000000 bits/s in slave mode.

Calling this function turns the SSC off until hsk_ssc_enable() is called.

Parameters

baud	The timer reload value for the baud rate generator, use SSC_BAUD to generate this value
config	The SSC configuration byte, use SSC_CONF to generate it
mode	Select master or slave operation

void hsk_ssc_ports

(

const ubyte

ports

)

Configure the I/O ports of the SSC unit.

Warning

Do not use when the SSC is enabled.

Parameters

ports

Selects an SSC I/O Ports I/O port configuration

void hsk_ssc_talk	(	char *	buffer,
		ubyte	len
	)

Send and receive data.

The buffer with the given length should contain the data to transceive and will be filled with the received data upon completion.

The provided buffer needs to reside in xdata memory, e.g. to create and use a string buffer the following should work:

char xdata buffer[] = "20 character buffer.";
…
hsk_ssc_talk(buffer, sizeof(buffer) - 1);

Note that char must not be const and that is used to prevent sending and overwriting the terminal 0 character. There may be cases where a terminal 0 character is desired.

Parameters

buffer	The rx/tx transmission buffer
len	The length of the buffer