FTBF » Wire Chamber DAQ

Methods from WireChamberController.py.

def checkForNewData(self):
        self.checkForReadoutError()
        bit = self.readoutDoneBit
        self.readoutDoneBit = self.tdcReadoutDone()
        self.readoutBusyCount= self.readoutBusyCount + self.tdcReadoutBusy()
        if self.readoutDoneBit - bit > 0:
            self.readoutBusyCount=0
            return 1
        return 0

def checkForReadoutError(self):
        if self.readoutBusyCount > 10:
            raise RuntimeError('Wire chamber readout has stalled.')

self.tdcReadoutDone() - check bit 1 in spill state register (addr=0xB)
self.tdcReadoutBusy() - check bit 0 in spill state register (addr=0xB)

Bill Badgett readout the wire chambers with his daq code yesterday (8/13) afternoon. Here are his results.

"The Lariat readout worked OK for a few spills; switching to the python readout, the first spill (~4000 triggers) it crashed. Subsequent few spills with lower triggers (~1000) have not crashed."

It looks like ~10 seconds is not long enough to transfer all the TDC data to the controllers when the spill ends.

Here is the logic Bill uses in his DAQ code to see when the wire chamber data is ready in the controller.

  bool tdcBusy = true;
  bool tdcDone = false;
  bool eotComplete = false;
  int ctr = 0;
  while ( !tdcDone && !eotComplete && tdcBusy && ( ctr<1000))
  {
    uint16_t data = read(SPILL_STATE_ADDR);
    tdcBusy = ( data >> TDC_READOUT_BUSY_S ) & 0x1;
    tdcDone = ( data >> TDC_READOUT_DONE_S ) & 0x1;
    eotComplete = ( data >> EOT_COMPLETE_S ) & 0x1;
    ctr++;
  }

This is called after the end-of-spill flag is found to go from 1 to 0.

I'm relying on the network latency of the read() call to be about one millsecond (OOM) so the timeout would be on the order of second(s). I have seen timeouts in the past, but I don't remember the circumstances.