Silicon Laboratories Stepper Machine Bedienungsanleitung PDF herunterladen (Seite 33)

AN155

Rev. 1.1 33

// readc()

// The readc() function is the lowest level function which provides

// direct access to the read buffer. It reads one character from the

// read buffer.

// Note that readc will wait if the read buffer is empty. This is usually

// desired if the program is waiting for user input.

// readc is a driver function and is closely integrated with the ISR.

// UART interrupts are temporarily disabled while the buffer is updated,

// This prevents the ISR from modifying the buffer and counter values

// during processing. That would be bad.

char readc(void)

{

char theChar; // the character to return

signed char i; // signed value to build location

while (readCount==0); // wait here if buffer empty [blocking]

ES0 = 0; // disable UART interrupts

i = readIndex - readCount; // back up by readcount

if (i < 0) // fix value if out of range

i+=READ_BUFFER_SIZE;

theChar = readBuffer[i]; // get character from read buffer

readCount--; // one less character in the buffer

ES0 = 1; // enable UARt interrupt

return theChar; // return the character

}

//-----------------------------------------------------------------------------

// writec()

// The writec() function is the lowest level function which allows access

// to the write buffer. It writes one character to the write buffer.

// Note that writec will wait if the write buffer is full. This is usually

// desired to prevent the write buffer from overflowing.

// writec is a driver function and is closely integrated with the ISR.

// UART interrupts are temporarily disabled while the buffer is updated to

// prevent the ISR from modifying the buffer and counter values during

// processing. That would be bad.

void writec(char theChar)

{

// wait here if full [blocking]

while (writeCount >= WRITE_BUFFER_SIZE);

ES0 = 0; // disable UART interrupts

writeBuffer[writeIndex] = theChar; // put character in buffer at writeIndex

writeIndex++; // increment index

if (writeIndex >= WRITE_BUFFER_SIZE)// fix if out of range

writeIndex = 0;

writeCount++; // one more character in buffer

if(TX_Idle) // if transmitter idle flag set

{

TI0 = 1; // force TX interrupt

TX_Idle = 0; // idle no more

}

ES0 = 1; // enable UART interrupts

1 2 ... 28 29 30 31 32 33 34 35 36

Kommentare zu diesen Handbüchern

Keine Kommentare

Silicon Laboratories Stepper Machine Bedienungsanleitung Seite 33

Kommentare zu diesen Handbüchern

Verwandte Produkte und Handbücher für Stepper Silicon Laboratories Stepper Machine