Automotive Connectivity

EMI

Each time we transmit a signal on a medium, we experience noise that affects our signal:

The analog information is always affected by noise, while the digital information can only be right or wrong:

Analog Signals:

An analog signal absorbs the noise that becomes part of the information itself. The only solution is filtering.

Digital Signals:

The information is encapsulated in a sequence of 1 and 0. If we are still able to distinguish well between 1 and 0, even with the noise, we are errorless and noise immune. If the noise is too strong to change a bit, we have an error.

Vehicular Communications:

Intra-vehicular and inter-vehicular communications are digital, but there is an easy experiment to realize how much a car is "noisy".

Analog Communication - Volume Game:

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On Board Tour & Recap

We need more:

• From intra-vehicle to inter-vehicle communication more data
• From Driver Assistance to ADAS more data & QoS
• Increasing usage of Infotainment more

ECUs HW & SW

domenica 15 novembre 2020 17:22

Typical ECUs:

• Middle and upper class vehicles carry 80-100 networked ECUs.

Each ECU consists of:

• Transceiver.
• Power supply.
• Sensor/Actor drivers.
• ECU Core (hw/sw). Also includes the Controller.

ECU and components must be:

• Shock resistant.
• Rust proof.
• Water/Oil/Heat resistant.

ECU Architecture

The Core is close to a Personal Computer, and we also have an additional external guard software (exwatchdog) for safety critical applications:

Until now, we have seen communication and diagnosis parts.

Inside the Microcontroller (MCU)

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Typical Architecture of the Micro Control Unit (MCU):

Microcontroller (MCU):

• 8, 16, 32 Bit Architecture.
• Infineon, Freescale, Fujitsu, …

Memory:

• Volatile Memory: RAM.
• Non-Volatile memory: Flash or Serial EEPROM.

Power supply:

• DC/DC Converter, to 5V or

1. watchdog does not receive any kick after a specific period, it resets the ECU and notifies the entire system if necessary.
2. Application Specific Integrated Circuit (ASIC):
• The opposite of a general purpose PC.
• CMOS technology (highest density and lowest cost).
• Often designed and produced for a specific customer.
3. ECU Operating Systems
• OSEK/VDK
• In English "Open Systems and their Interfaces for the Electronics in Motor Vehicles".
• Characteristics:
• Embedded operating system, for single processor.
• Static configuration:
• Tasks.
• Resources.
• Functions.
• Hard deadlines available (like FlexRay).
• Programs execute directly from ROM (coded in the stone).
• Very low memory requirements.
• Standardized system.
• Configuration:
• Operating system configured at compile time.
• OSEK Implementation Language (OIL):
• Scheduling strategy.
• Task priorities.
• Tasks:
• Static priority.
• Relationships of tasks (synchronization, message exchange, signaling).
• Error management.
• C macros for

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Tasks:

A task is a piece of code responsible of something.

Suspended: not running at all.

Ready: ready and waiting for the CPU.

Running: core of the task is executing.

Waiting: the task is waiting for an event.

Task vs Scheduler: The scheduler is a software that decides the order of execution of tasks. The dispatcher physically takes the tasks from the scheduler and provides them to the CPU.

Scheduling:

Scheduler always chooses the highest priority task.

Configurable modes:

• Non preemptive: tasks/ECUs are never preempted (mai anticipati) (like CAN, FlexRay, MOST). While we are transmitting, no one can steal the bus.
• Preemptive: higher priority tasks always preempt lower priority tasks (ex. figure).
• Mixed: individual configuration of each task (like OPEN: express packets are preemptive and can preempt other packets, while standard packets are non preemptive and cannot interrupt other packets).

Figure example: T1 is running, T2 has...

complexity also of a group of ECUs in terms of communication.

3. Basic Software (BSW): standardized software modules (mostly) without any functional job itself, that offer services necessary to run the functional part of the upper software layer.

BSW is divided in three major layers and complex drivers:

• Services Layer: functional group subdivision (memory, communication services).
• ECU Abstraction Layer.
• Microcontroller Abstraction Layer.

Services communicate via Virtual Functional Bus (VFB). VFB handles communication between ECUs.

4. Microcontroller: last layer; the place in which OSEK/VDX does everything.

AUTOSAR Software Components Communication via VFB:

The AUTOSAR Software Components (SW-C) encapsulate an application which runs on the AUTOSAR infrastructure. It has well-defined interfaces, which are described and standardized.

VFB is the sum of all communication mechanisms (and interfaces) provided by AUTOSAR on an abstract level (technology independent). This is how we code the software.

logically connecting pieces together.

Deployment tools and Mapping on ECUs:

We also have deployment tools: they know the ECU descriptions and the system constraints.

- At the end, we have some pieces of software running on a specific ECU.

- RunTime Environment (RTE): collects the connections that we have to provide. It implements the VFB functionality on a specific ECU.

Basic Software (BSW): it provides the infrastructure for the execution on an ECU.

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GPS

sabato 21 novembre 2020 17:40

Global Positioning System (GPS) is a space-based satellite navigation system which provides location and time information in all weather:

Space-based: XYZ coordinates.

Satellite: expensive hi-tech devices in orbit, always running.

Navigation system: if you want to know how to reach where you want to go, you need to know where you are.

Location and time: space and time are strongly connected to understand GPS.

All weather: we do not refer only to

Non ci sono più notti nuvolose (i sistemi di navigazione precedenti si basavano sull'osservazione delle stelle). Il nome ufficiale è NAVSTAR GPS (Navigational Satellite Timing and Ranging Global Positioning System). Attori del GPS: Segmento spaziale: dispositivi satellitari, che trasmettono costantemente messaggi di navigazione. Segmento di controllo: antenne terrestri che tracciano, raccolgono e correggono tutte le orbite dei satelliti. Ricevono e trasmettono dati da/a satellite. Segmento utente: dispositivi economici utilizzati per raccogliere segnali GPS e conoscere la posizione. I dispositivi utente possono solo ricevere dati dal satellite. Messaggio di navigazione Le informazioni trasmesse dai satelliti sono chiamate messaggio di navigazione (NAV). Il messaggio NAV è simile a un messaggio MOST. NAV è composto da 25 frame (o pagine) di 30 secondi ciascuno che formano i frame principali, che impiegano 12,5 minuti per essere trasmessi. Un frame è composto da 5 sub-frame e richiede 30 secondi (6 secondi ciascuno). ○ Sub-frame 1: orologio del satellite

info.

• Sub-frame 2-3: satellite ephemeris (orbits).
• Sub-frame 4-5: almanac and constellation status.

Sub-frames 1, 2, 3 are transmitted with each frame, always the same, while sub-frames 4, 5 are different and are complete only receiving all the 25 frames of the master frame.

To understand were we are, we only need to wait between 6 sec (1 sub-frame) and 30 sec (1 frame).

One sub-frame is composed by 10 words, and