Specifications

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A description of the varying hand held unit machine states is as follows.
HHU Reading State – Read in input from the sensor, allow only the push button
to interrupt the process. The software should take in data from the sensor and
save that into memory. If the interrupt has not been enabled then it will transfer to
the Processing State.
HHU Processing State – The data will be processed with using a module that
will check for errors. After the data has been completely collected it will be
processed and converted from analog signal to digital signal. Once the data has
been presented in digital, then the next step is to convert the digital signal into a
BAC value. There software should check and see if there was any data lose. If
the data has been lost, then an error module should be able to handle the fault.
The only way to interrupt this process is to hit the push button. Holding the push
button will enable interrupt. The data will stop being collected and wait for user
input. If the interrupt is not enabled and everything is collected correctly then the
state will change to Display State/Transfer.
HHU Display State/Transfer – Display mode allows the data that was collected
and processed by the processor to be displayed on the LCD screen and
transferred the calculated BAC value to control box unit. The data collected is
passed to the display handler. When there is data processed and collected, the
display handler will behave differently depending on the value. The software
transfers the BAC value wirelessly to the control box. If all data has been
transferred correctly, the hand held unit should receive a message and reset the
state back to Reading State.
The control unit system will behave differently. The software for control box unit
will require sending a request to the hand held unit to check for a response. If a
response comes back to the control box, then the receive transmission module
will be called. The control box run in the following states shown in Figure 2.6.1.3:
CBU Receive Transmission State – The receive transmission module will be
called and the control box unit will start to receive data from the hand held unit.
An error check module specifically for the control box unit will be used to check
the data bits and see if there was any data lost during the broadcast. Once the
data has been received and that data is valid, the broadcast will run the next
state which is Enable System Functionality.
CBU Enable Functionality State – In the beginning the software should lock all
access to starting the car. Once the value from the hand held unit has been
received then depending on what value it is, the software will react accordingly to
the data. The data will be passed through a validation module. If the validation
shows that the user is capable for driving then the System Mode will set to 01.
The System Mode will have two modes, 00 or 01. When the System Mode is
enabled, the software control box unit will switch to the idle state.