// Pause for exactly 'tick' number of ticks = 0.25us
void tickDelay(int tick); // Implementation is platform specific
// 'tick' values
int A,B,C,D,E,F,G,H,I,J;
//-----------------------------------------------------------------------------
// Set the 1-Wire timing to 'standard' (standard=1) or 'overdrive' (standard=0).
//
void SetSpeed(int standard)
{
// Adjust tick values depending on speed
if (standard)
{
// Standard Speed
A = 6 * 4;
B = 64 * 4;
C = 60 * 4;
D = 10 * 4;
E = 9 * 4;
F = 55 * 4;
G = 0;
H = 480 * 4;
I = 70 * 4;
J = 410 * 4;
}
else
{
// Overdrive Speed
A = 1.5 * 4;
B = 7.5 * 4;
C = 7.5 * 4;
D = 2.5 * 4;
E = 0.75 * 4;
F = 7 * 4;
G = 2.5 * 4;
H = 70 * 4;
I = 8.5 * 4;
J = 40 * 4;
}
}
下記の例2は、1-Wireの基本オペレーションのサンプルコードを示しています。
例2. 1-Wireの基本関数
//-----------------------------------------------------------------------------
// Generate a 1-Wire reset, return 1 if no presence detect was found,
// return 0 otherwise.
// (NOTE: Does not handle alarm presence from DS2404/DS1994)
//
int OWTouchReset(void)
{
int result;
tickDelay(G);
outp(PORTADDRESS,0x00); // Drives DQ low
tickDelay(H);
outp(PORTADDRESS,0x01); // Releases the bus
tickDelay(I);
result = inp(PORTADDRESS) & 0x01; // Sample for presence pulse from slave
tickDelay(J); // Complete the reset sequence recovery
return result; // Return sample presence pulse result
}
//-----------------------------------------------------------------------------
// Send a 1-Wire write bit. Provide 10us recovery time.
//
void OWWriteBit(int bit)
{
if (bit)
{
// Write '1' bit
outp(PORTADDRESS,0x00); // Drives DQ low
tickDelay(A);
outp(PORTADDRESS,0x01); // Releases the bus
tickDelay(B); // Complete the time slot and 10us recovery
}
else
{
// Write '0' bit
outp(PORTADDRESS,0x00); // Drives DQ low
tickDelay(C);
outp(PORTADDRESS,0x01); // Releases the bus
tickDelay(D);
}
}
//-----------------------------------------------------------------------------
// Read a bit from the 1-Wire bus and return it. Provide 10us recovery time.
//
int OWReadBit(void)
{
int result;
outp(PORTADDRESS,0x00); // Drives DQ low
tickDelay(A);
outp(PORTADDRESS,0x01); // Releases the bus
tickDelay(E);
result = inp(PORTADDRESS) & 0x01; // Sample the bit value from the slave
tickDelay(F); // Complete the time slot and 10us recovery
return result;
}
//-----------------------------------------------------------------------------
// Write 1-Wire data byte
//
void OWWriteByte(int data)
{
int loop;
// Loop to write each bit in the byte, LS-bit first
for (loop = 0; loop < 8; loop++)
{
OWWriteBit(data & 0x01);
// shift the data byte for the next bit
data >>= 1;
}
}
//-----------------------------------------------------------------------------
// Read 1-Wire data byte and return it
//
int OWReadByte(void)
{
int loop, result=0;
for (loop = 0; loop < 8; loop++)
{
// shift the result to get it ready for the next bit
result >>= 1;
// if result is one, then set MS bit
if (OWReadBit())
result |= 0x80;
}
return result;
}
//-----------------------------------------------------------------------------
// Write a 1-Wire data byte and return the sampled result.
//
int OWTouchByte(int data)
{
int loop, result=0;
for (loop = 0; loop < 8; loop++)
{
// shift the result to get it ready for the next bit
result >>= 1;
// If sending a '1' then read a bit else write a '0'
if (data & 0x01)
{
if (OWReadBit())
result |= 0x80;
}
else
OWWriteBit(0);
// shift the data byte for the next bit
data >>= 1;
}
return result;
}
//-----------------------------------------------------------------------------
// Write a block 1-Wire data bytes and return the sampled result in the same
// buffer.
//
void OWBlock(unsigned char *data, int data_len)
{
int loop;
for (loop = 0; loop < data_len; loop++)
{
data[loop] = OWTouchByte(data[loop]);
}
}
//-----------------------------------------------------------------------------
// Set all devices on 1-Wire to overdrive speed. Return '1' if at least one
// overdrive capable device is detected.
//
int OWOverdriveSkip(unsigned char *data, int data_len)
{
// set the speed to 'standard'
SetSpeed(1);
// reset all devices
if (OWTouchReset()) // Reset the 1-Wire bus
return 0; // Return if no devices found
// overdrive skip command
OWWriteByte(0x3C);
// set the speed to 'overdrive'
SetSpeed(0);
// do a 1-Wire reset in 'overdrive' and return presence result
return OWTouchReset();
}
//-----------------------------------------------------------------------------
// Read and return the page data and SHA-1 message authentication code (MAC)
// from a DS2432.
//
int ReadPageMAC(int page, unsigned char *page_data, unsigned char *mac)
{
int i;
unsigned short data_crc16, mac_crc16;
// set the speed to 'standard'
SetSpeed(1);
// select the device
if (OWTouchReset()) // Reset the 1-Wire bus
return 0; // Return if no devices found
OWWriteByte(0xCC); // Send Skip ROM command to select single device
// read the page
OWWriteByte(0xA5); // Read Authentication command
OWWriteByte((page << 5) & 0xFF); // TA1
OWWriteByte(0); // TA2 (always zero for DS2432)
// read the page data
for (i = 0; i < 32; i++)
page_data[i] = OWReadByte();
OWWriteByte(0xFF);
// read the CRC16 of command, address, and data
data_crc16 = OWReadByte();
data_crc16 |= (OWReadByte() << 8);
// delay 2ms for the device MAC computation
// read the MAC
for (i = 0; i < 20; i++)
mac[i] = OWReadByte();
// read CRC16 of the MAC
mac_crc16 = OWReadByte();
mac_crc16 |= (OWReadByte() << 8);
// check CRC16...
return 1;
}
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