The FEE Server Control Engine of the ALICE-TRD - Westfälische ...

5 The FEEServer Control Engine
the ADC values UADC to a temperature is done with the formula
temperature in°C =
) − 11.6753
°C − 273.15°C (5.2)
−0.0394864
ln( 3.3−UADC
UADC
The calibration values and most of the functions in the classes adc_device, voltage_sensor
and temp_sensor were taken from existing C programs.
The temperature sensor readout in the MCMs requires more elaborate readout functions.
In principle, each MCM temperature sensor requires an individual calibration.
Furthermore the sensors do not work reliably and therefore a runtime identification of
non-working sensors is required. In this section only the main functions used for the
temperature readout are described. A detailed description of the temperature sensors
themself is given in chapter 6.
The class TempControl (trdce) encapsulates the readout of the temperature sensors.
Each time the function void TempControl::measure(void) is called, the current temperature
sensor value of all MCMs on the readout chamber is read out and printed to the logging
system. An example of the output in case of printing absolute ADC values is given in
listing 6.1 on page 79. The output format can be set via the extended SCSN command
SCSN_CMD_MCMTEMP (see table B.2). To read out the sensors, first a write frame is
send to all MCMs to trigger a measurement and afterwards the measured values are read
out via SCSN read frames.
TempControl provides the function TempControl::learnConfig(struct cfdat_temp_calib * ) to
set calibration values for each MCM individually. However, it turned out that an individual
calibration of the temperature sensors is not feasible (see chapter 6). Therefore
TempControl::learnConfig(struct cfdat_temp_calib * ) is mainly kept for historical reasons.
As a consequence, the function void TempControl::measure(void) cannot print meaningful
temperatures but prints out the raw ADC values of the temperature sensors or the difference
between the first measured ADC value after switching on the MCMs and the current
ADC value, depending on configuration.
The identification of non-working temperature sensors is performed during the transition
from STDBY to STDBY_INIT. The function CEStateMachine::triggerTransition() calls
TempControl::apply(void). This function reads out each MCM temperature sensor ten
times and stores the results in the instances of MCMChip. For each MCM the class
TempControl contains one instance of class MCMChip which stores the last ten sensor readings
and status information.
Afterwards the function bool TempControl::calcStatus(void) is called. This function calls
bool MCMChip::calcStatus(void) for each instance. bool MCMChip::calcStatus(void) uses the
previously stored ten values to check if the temperature sensor does work or not and
sets the corresponding status in class MCMChip. Then bool TempControl::calcStatus(void)
counts the number of non-working sensors. If this number is below a threshold which
can be set via the extended SCSN command SCSN_CMD_MCMTEMP (see table B.2), the
MCMs are switched off for a short time. It turned out that this procedure increases the
number of working sensors significantly (see chapter 6). After the MCMs were switched
on again, the identification procedure is repeated.
In the output of void TempControl::measure(void) non-working sensors are represented
by -1 in case of the absolute ADC values are printed since the possible range for real
values is 0 to 1023, or by 999 in case of ADC differences are printed out.
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