byte MP3Player::i2c_rx(byte ack)
{
byte x, d=0;
SDA_H();
for(x=0; x<8; x++)
{
d <<= 1;
do {
SCL_H();
}
while(SCL_IN()==0); // wait for any SCL clock stretching
i2c_dly();
if(SDA_IN()) d |= 1;
SCL_L();
}
if(ack)
{
SDA_L();
}
else
{
SDA_H();
}
SCL_H()
i2c_dly(); // send (N)ACK bit
SCL_L();
SDA_H();
return d;
}
/*whenever reach here, the SCL is low, so enable change SDA*/
unsigned char i2c_rx(char ack)
{
char x, d=0;
SDA = 1; //release SDA to slave
for(x=0; x<8; x++) {
d <<= 1;
do {
SCL = 1; //master pull up clock(slave might hold clk for clock sync)
}
while(scl_in()==0); //wait for any SCL clock stretching (clock sync)
/*slave data ready and relase clock*/
i2c_dly();
if(sda_in()) d |= 1; /*input the bit*/
SCL = 0; //done this bit( slave now prepare next bit, and hold clock for clock sync)
}
//bit 9, master might sending ACK bit
if(ack) SDA = 0;
else SDA = 1;
SCL = 1; //master ACK bit ready, relase clock
/*here need wait clock to sync, i.e, slave is reading the bit*/
while(scl_in()==0); /*by hyl*/
i2c_dly();//send (N)ACK bit
SCL = 0; //
SDA = 1;
return d;
}
void i2c_stop(void)
{
SDA = 0; // i2c stop bit sequence
i2c_dly();
SCL = 1;
i2c_dly();
SDA = 1;
i2c_dly();
}
void MP3Player::i2c_stop(void)
{
SDA_L(); // i2c stop bit sequence
i2c_dly();
SCL_H();
i2c_dly();
SDA_H();
i2c_dly();
}
void i2c_start(void)
{
/*only the start stop allow change SDA while the SCL keep high*/
SDA = 1; // i2c start bit sequence
i2c_dly();
SCL = 1; // Clock is high, SDA from high to low
i2c_dly();
SDA = 0;
i2c_dly();
SCL = 0; //master pull down clock,and prepare SDA to slave (Address)
i2c_dly();
}
byte MP3Player::i2c_tx(byte d)
{
byte x;
byte b;
for(x=8; x; x--)
{
if(d&0x80)
{
SDA_H();
}
else
{
SDA_L();
}
SCL_H();
d <<= 1;
SCL_L();
}
SDA_H();
SCL_H();
i2c_dly();
b = SDA_IN(); // possible ACK bit
SCL_L();
return b;
}
/*clock from low to high might need deal with clock sync*/
unsigned char i2c_tx(unsigned char d)
{
char x;
static bit nack;
//prepare data
for(x=8; x; x--) {
if(d&0x80) SDA = 1;
else SDA = 0;
i2c_dly();
SCL = 1; //data ready, relase clock
d <<= 1;
i2c_dly(); //dont need?, by hyl
i2c_dly(); //dont need?, by hyl
SCL = 0; //master is prepareing next bit
i2c_dly(); //dont need?, by hyl
}
//reive the ACK
SDA = 1; //relase contorl the SDA pin ready for input ?
i2c_dly(); //wait the ack
SCL = 1; //the bit 9 clock event, might a ACK
i2c_dly();
nack = sda_in(); // possible ACK bit
if(nack)
; //should end transimition and abort with stop....
SCL = 0; /*end the tx*/
return b;
}
