public MCP23S17GpioProvider(byte spiAddress, int spiChannel, int spiSpeed) throws IOException {
// setup SPI for communication
int fd = Spi.wiringPiSPISetup(spiChannel, spiSpeed);
if (fd <= -1) {
throw new IOException("SPI port setup failed.");
}
// set all default pins directions
write(REGISTER_IODIR_A, (byte) currentDirectionA);
write(REGISTER_IODIR_B, (byte) currentDirectionB);
// set all default pin interrupts
write(REGISTER_GPINTEN_A, (byte) currentDirectionA);
write(REGISTER_GPINTEN_B, (byte) currentDirectionB);
// set all default pin interrupt default values
write(REGISTER_DEFVAL_A, (byte) 0x00);
write(REGISTER_DEFVAL_B, (byte) 0x00);
// set all default pin interrupt comparison behaviors
write(REGISTER_INTCON_A, (byte) 0x00);
write(REGISTER_INTCON_B, (byte) 0x00);
// set all default pin states
write(REGISTER_GPIO_A, (byte) currentStatesA);
write(REGISTER_GPIO_B, (byte) currentStatesB);
// set all default pin pull up resistors
write(REGISTER_GPPU_A, (byte) currentPullupA);
write(REGISTER_GPPU_B, (byte) currentPullupB);
}
protected void write(byte register, byte data) {
// create packet in data buffer
byte packet[] = new byte[3];
packet[0] = (byte) (address | WRITE_FLAG); // address byte
packet[1] = register; // register byte
packet[2] = data; // data byte
// send data packet
Spi.wiringPiSPIDataRW(0, packet, 3);
}
protected byte read(byte register) {
// create packet in data buffer
byte packet[] = new byte[3];
packet[0] = (byte) (address | READ_FLAG); // address byte
packet[1] = register; // register byte
packet[2] = 0b00000000; // data byte
int result = Spi.wiringPiSPIDataRW(0, packet, 3);
if (result >= 0) return packet[2];
else throw new RuntimeException("Invalid SPI read operation: " + result);
}