...
Overview
The program will be controlled through the use of multiple Finite State Machines to ensure that inputs are only serviced at the appropriate periods. The system will use three state machines to :
Pedal State Machine:
This state machine governs the running state of the car and defines the conditions under which the driver can turn on and move the vehicle. Transitions for this FSM depend on the state of the directional state machine.
...
Off
...
Idle
...
Driving
...
Directional State Machine
Governs the possible gear shifts made by the user.
...
Turn Signal State Machine
Governs the states of the turn signals made by the driver. Independent from the other FSMs.
...
ADC Driver
On the STM32 is a 12-bit analog-to-digital converter (ADC). The role of an ADC is to take an analog signal as an input and give as output a digital number proportional to the magnitude of the input signal. The following formula can be used to determine the ADC reading:
The ADC on the STM32 has 19 multiplexed channels, allowing it to read signals from 16 external sources and 3 internal sources. The pin mappings for the 16 external sources are included below:
...
Analog-to-digital conversion of the different channels can be performed both single mode, in which the ADC converts all the channels at once in a single sequence of conversions, and continuous mode, where the device automatically restarts the scan after converting all of the different channels. The 12-bit value obtained from the conversion will be stored in the ADC read-only data register (ADC_DR).objective for the driver controls firmware is to create a robust system capable of both properly keeping track of the state of the vehicle when responding to user inputs, as well as being able to send out the correct messages to other subsystems of the car.
The driver controls system works by waiting for the user to take an action such as a button press, which will then be used to construct an event to push to a global queue. When the event is ready to be raised from this queue, the system observes the current state of the car to determine whether the event is safe to be processed at the current time. If an event is raised at an unsafe time (i.e. flooring it while in neutral), then the event will be discarded.
To monitor the current state of the car, a series of Finite State Machines is used to monitor each input device. The different states of each FSM have a corresponding check function, which can be used to approve or decline an event according to it's current state. An event arbiter module is then used to run the check functions of all active FSMs, and the event is only processed if they all determine the event to be safe to run.
Once a given event is processed, the FSMs change state to reflect the event. A CAN message is then sent to the relevant subsystem based on the data held in the event.
Sequence Diagram
