// FOUR 74HC595 SHIFT REGISTERS
// by paul
int32_t in1;

uint8_t *txbuf;

void setup(void) {

  static uint8_t _txbuf[32] __attribute__((section(".sram2")));
  txbuf = _txbuf;
}

void loop(void) {
  spiSelect(&SPID1);

  txbuf[0] = (in1 >> 24); // SHIFTREGISTER 1
  txbuf[1] = (in1 >> 16); // SHIFTREGISTER 2
  txbuf[2] = (in1 >> 8);  // SHIFTREGISTER 3
  txbuf[3] = (in1);       // SHIFTREGISTER 4

  spiSend(&SPID1, 4, txbuf);
  spiUnselect(&SPID1);
  chThdSleepMilliseconds(1);
}

msg_t ThreadX2() {
  setup();
  while (!chThdShouldTerminate()) {
    loop();
    chThdSleepMilliseconds(1);
  }
  chThdExit((msg_t)0);
}
static msg_t ThreadX(void *arg) { ((attr_parent *)arg)->ThreadX2(); }
WORKING_AREA(waThreadX, 1024);
Thread *Thd;

in1 = 0;
Thd = chThdCreateStatic(waThreadX, sizeof(waThreadX), NORMALPRIO, ThreadX,
                        (void *)this);

this->in1 = inlet_in;

chThdTerminate(Thd);
chThdWait(Thd);