Explanation of SMBus.c,h Defining SMBUS (I2C)-Related Procedures

SMBUS (I2C)

In many sample and application codes using TWENET, the I2C bus is typically not accessed directly through the low-level AHI library procedures.
Instead, a set of simplified read/write functions defined in SMBus.c and SMBus.h is used.

The following is a list of the function names provided:

void vSMBusInit(void);
void vSMBusInit_setClk(uint32 u32Clk);
void vSMBusDeInit();
void vSMBusDeInit(void);
bool_t bSMBusWrite(uint8 u8Address, uint8 u8Command,
						  uint8 u8Length, uint8* pu8Data);
bool_t bSMBusSequentialRead(uint8 u8Address, uint8 u8Length,
		   uint8* pu8Data);

SMBus.c SMBus.h

These are a set of functions summarizing typical I2C procedures, with source code stored in TWENETmwx/source/sensors/legacy.

• If the TWENETmwx library is not linked (C project), copy and use this source code.

vSMBusInit()

void vSMBusInit(void);

Initializes the I2C bus.
The pins used are DIO14 (CLK) and DIO15 (DATA), with a clock frequency of 100 Kbps.

vSMBusInit_setClk(uint32)

{{{cpp {noln=true} void vSMBusInit_setClk(uint32 u32Clk); }}}

Using this function instead of vSMBusInit() initializes the I2C bus with the clock specified by u32clk.

• If u32clk >= 7 and u32clk <= 255 ⇒ Initializes with clock frequency 3200000ul / (u32clk + 1). For example, specifying 31 gives 100 kHz, and 7 gives 400 kHz.
• If u32clk >= 12500 and u32clk <= 400000 ⇒ Initializes with u32clk directly.
• Otherwise ⇒ Undefined behavior.

※ The actual frequency will be the closest available based on the hardware clock divisor. For detailed calculations, refer to the source code (for TWELITE GOLD, see NXP’s FSL library specifications).

// Implementation for TWELITE GOLD
PUBLIC void  TWENET_smbus_vSMBusInit_setClk(uint32_t u32clk)
{
    ...
	if (u32clk >= 7 && u32clk <= 255) { // given by divisor
		u32clk = 3200000ul / (u32clk + 1);
	}

	if (u32clk < 12500ul || u32clk > 400000ul) {
		u32clk = 100000ul;
	}

	// initialize the I2C
    //... rest of the implementation
      _conf.baudRate_bps = u32clk;
      I2C_MasterGetDefaultConfig(&_conf); // FSL library function
}

// Implementation for TWELITE BLUE/RED
void vSMBusInit_setClk(uint32 u32Clk)
{
    /* convert clock to clock divisor */
    if (u32Clk > 255) {
    	u32Clk = (3200000UL / u32Clk) - 1;
    }
    if (u32Clk < 7 || u32Clk > 255) u32Clk = 31; // set 100kHz

    /* run bus at specified value */
    vAHI_SiMasterConfigure(TRUE, FALSE, u32Clk);
    // 16/[(PreScaler + 1) x 5]MHz
    //		--> 31:100KHz, 7:400KHz, 47:66KHz
}

vSMBusDeInit()

void vSMBusDeInit();

Stops the use of the I2C bus.

• For TWELITE BLUE/RED, calls vAHI_SiMasterDisable().
• For TWELITE GOLD, stops the I2C bus usage and restores DIO14 and DIO15 pins to the TWENET library’s initial configuration (input ports with pull-up).

bSMBusWrite()

bool_t bSMBusWrite(
	uint8 u8Address,
    uint8 u8Command,
	uint8 u8Length,
    uint8* pu8Data)

Performs a write operation on the I2C bus.

• u8Address ⇒ Specifies the device address on the I2C bus.
• u8Command ⇒ Specifies the command (first transfer byte) for the write operation.
• u8Length ⇒ Number of subsequent bytes. If 0, only the command byte is transferred. If greater than 0, pu8Data must be defined.
• pu8Data ⇒ Pointer to the memory area containing the bytes to be transferred.

Returns TRUE if the transfer succeeds, and FALSE if it fails.

bSMBusSequentialRead()

bool_t bSMBusSequentialRead(
    uint8 u8Address,
    uint8 u8Length,
	uint8* pu8Data)

Performs a read operation on the I2C bus.

• u8Address ⇒ Specifies the device address on the I2C bus.
• u8Length ⇒ Specifies the number of bytes to read (must be 1 or more).
• pu8Data ⇒ Pointer to the memory area where the read bytes will be stored.

Returns TRUE if the transfer succeeds, and FALSE if it fails.

Others

Handling During Sleep

• For TWELITE BLUE/RED, hardware reinitialization is required after waking from sleep.
  If vSMBusDeInit() is not called, the pin state is undefined (or follows the JN516x peripheral specification).
  You can reinitialize by calling vSMBusInit() or vSMBusInit_setClk() again.

• For TWELITE GOLD, the behavior is as follows:

  • RAM ON (normal) sleep: If the I2C bus was initialized before sleep, it will be reinitialized upon waking. If the I2C bus was not in use, normal general-purpose IO wake-up handling will apply.
  • RAM OFF (deep) sleep: Upon waking, TWENET will reinitialize the pins as input pins with pull-up enabled.

TWELITE GOLD Implementation

AHI-compatible functions are not provided; instead, corresponding functions are implemented in SMBus.c and SMBus.h.

// Implementations in the TWENETcmpt library
PUBLIC void TWENET_smbus_vSMBusInit(void);
PUBLIC void TWENET_smbus_vSMBusDeInit(void);
PUBLIC void TWENET_smbus_vSMBusInit_setClk(uint32 u32clk);
PUBLIC bool_t  TWENET_smbus_bSMBusWrite(uint8 u8Address,
    uint8 u8Command, uint8 u8Length, uint8* pu8Data);
PUBLIC bool_t TWENET_smbus_bSMBusSequentialRead(uint8 u8Address,
    uint8 u8Length,  uint8* pu8Data);

// SMBus.h uses inline definitions to call the above functions
static inline void vSMBusInit(void) {
	TWENET_smbus_vSMBusInit();
}
static inline void vSMBusInit_setClk(uint32 u32Clk) {
	TWENET_smbus_vSMBusInit_setClk(u32Clk);
}
static inline void vSMBusDeInit() {
	TWENET_smbus_vSMBusDeInit();
}
static inline void vSMBusDeInit(void) {
	TWENET_smbus_vSMBusInit();
}
static inline bool_t bSMBusWrite(uint8 u8Address, uint8 u8Command,
						  uint8 u8Length, uint8* pu8Data) {
	return TWENET_smbus_bSMBusWrite(u8Address, u8Command, u8Length, pu8Data);
}
static inline bool_t bSMBusSequentialRead(uint8 u8Address, uint8 u8Length,
		   uint8* pu8Data) {
	return TWENET_smbus_bSMBusSequentialRead(u8Address, u8Length, pu8Data);
}