void write_bit( bool x ){
scl.set( 0 );
wait_half_period();
sda.set( x );
scl.set( 1 );
wait_half_period();
}
/// write and read to (and from) a spi chip
//
/// This function performs an n byte write-and-read operation on the
/// SPI chip activated by the (active low) sel pin.
///
/// When either writing or reading is not needed the corresponding
/// argument can be a nullptr.
void write_and_read(
pin_out & sel,
int n,
const byte data_out[],
byte data_in[]
) override {
sel.set( 0 );
for( int i = 0; i < n; ++i ){
byte d =
( data_out == nullptr )
? 0
: *data_out++;
for( int j = 0; j < 8; ++j ){
mosi.set( ( d & 0x80 ) != 0 );
wait_half_period();
sclk.set( 1 );
wait_half_period();
d = d << 1;
if( miso.get() ){
d |= 0x01;
}
sclk.set( 0 );
}
if( data_in != nullptr ){
*data_in++ = d;
}
}
wait_half_period();
sel.set( 1 );
wait_half_period();
}
void write_stop(){
scl.set( 0 );
wait_half_period();
sda.set( 0 );
wait_half_period();
scl.set( 1 );
wait_half_period();
sda.set( 1 );
wait_half_period();
}
bool read_bit(){
scl.set( 0 );
sda.set( 1 );
wait_half_period();
scl.set( 1 );
wait_half_period();
bool result = sda.get();
wait_half_period();
return result;
}
void write_start(){
sda.set( 0 );
wait_half_period();
scl.set( 0 );
wait_half_period();
}