bool PBBP::receiveAck() {
bool first, second;
if (!receiveBit(&first) || !receiveBit(&second))
return false;
// Acks are sent as 01, nacks as 10. Since the 0 is dominant during
// a bus conflict, a receiveing of 00 means both an ack and a nack was
// sent.
if (!first && !second ) {
this->last_error = ACK_AND_NACK;
return false;
} else if (!second ) {
// Read error code from the slave
if (receiveByte(&this->last_slave_error)) {
this->last_error = NACK;
} else {
this->last_error = NACK_NO_SLAVE_CODE;
}
return false;
} else if (first) {
this->last_error = NO_ACK_OR_NACK;
return false;
} else {
return true;
}
}
bool PBBP::receiveByte(uint8_t *b) {
bool parity_val = 0;
*b = 0;
uint8_t next_bit = 0x80;
bool value;
// Receive data bits
while (next_bit) {
if (!receiveBit(&value))
return false;
if (value) {
*b |= next_bit;
parity_val ^= 1;
}
next_bit >>= 1;
}
// Receive parity bit
if (!receiveBit(&value))
return false;
if (value == parity_val) {
this->last_error = PARITY_ERROR;
return false;
}
return receiveReady() && receiveAck();
}
bool PBBP::receiveReady() {
int timeout = this->max_stall_bits;
while (timeout--) {
bool value;
if (!receiveBit(&value))
return false;
// Ready bit?
if (value)
return true;
}
this->last_error = STALL_TIMEOUT;
return false;
}
// receiver: decode received bits. Ns samples per bit.
Bits
BluetoothReceiver::receive(const Signal& input) {
// Input length should be a multiple of Ns
int nBits = input.size()/Ns;
_ASSERTE((input.size()) % Ns == 0);
Bits bitsOut(nBits);
for (int i=0; i<nBits; ++i) {
slice sl_i(i*Ns, Ns);
bitsOut[i] = receiveBit(input[sl_i]);
}
return bitsOut;
}
