Silicon Laboratories Stepper Machine Bedienungsanleitung PDF herunterladen (Seite 36)

AN428

36 Rev. 0.6

// Parameters :

// 1) unsigned char addr - address to read data from the device

// range is full range of character: 0 to 255

// This function returns a single byte from location <addr> in the device then

// polls the <SMB_BUSY> flag until the read is complete.

U8 I2C_ByteRead (U8 addr)

{

U8 return_val; // Holds the return value

while (SMB_BUSY); // Wait for SMBus to be free.

SMB_BUSY = 1; // Claim SMBus (set to busy)

// Set SMBus ISR parameters

TARGET = SLAVE_ADDR<<1; // Set target slave address

SMB_RW = WRITE; // A random read starts as a write

// then changes to a read after

// the repeated start is sent. The

// ISR handles this switchover if

// the <SMB_RANDOMREAD> bit is set.

SMB_SENDWORDADDR = 1; // Send Word Address after Slave Address

SMB_RANDOMREAD = 1; // Send a START after the word address

SMB_ACKPOLL = 1; // Enable Acknowledge Polling

// Specify the Incoming Data

WORD_ADDR = addr; // Set the target address in the

// devices's internal memory space

pSMB_DATA_IN = &return_val; // The incoming data pointer points to

// the <retval> variable.

SMB_DATA_LEN = 1; // Specify to ISR that the next transfer

// will contain one data byte

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Silicon Laboratories Stepper Machine Bedienungsanleitung Seite 36