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Microcontroller-based systems are becoming more sophisticated, bringing new capabilities to automotive applications and new challenges for these product certification projects.

With the increasing use of RF technologies such as Bluetooth and Wi-Fi, there is a higher demand for addressing regulatory compliance and legal liability issues. These issues include compatibility between new technologies, conflicts between new and old technologies, and the impact on the safety of critical safety systems.

Bluetooth provides customers with highly transparent added value that not only influences purchase decisions, but also enables cost-effectiveness and paving the way for entry into the automotive industry. This challenge brings customer-focused technology to industries that are increasingly demanding reliability, electromagnetic compatibility/sensitivity (EMC/EMS), and high-quality design/manufacturing methods.

The advent of new technologies requires a rigorous exploration of potential product failure modes, which may involve complex interactions between systems. Product design engineers are now aware that from the beginning of the product development cycle to the installation and use phases, it is important to identify potential non-compliance with regulatory issues and risks, and to apply planned design and inspection measures. In automotive applications, the United States Federal Communications Commission (FCC), Bluetooth Certification Organization (BQB), Underwriters Laboratories (UL) and European organizations have developed regulatory requirements that are relevant to microcontroller applications in the automotive industry. The hardware and software features are related. Affecting the choice of a suitable microcontroller can help design engineers avoid excessive development costs and the time-to-market impact of correcting mis-options during product development. Finally, this article provides a certification test summary rather than a single test data for each fuselage in order to avoid redundant tasks in order to meet the repetitive requirements of automotive applications, FCC and BQB.

2.0 Management Regulations in Microcontroller Applications

Before discussing the details of Bluetooth-specific requirements, review the general requirements for microcontrollers in the automotive industry. These requirements include:
· EMC/EMS requirements for automotive and FCC/CE certification · Electrical safety specified by Underwriters Laboratories (UL) · Automotive-specific quality/safety testing

2.1 EMC/EMS requirements

Since the FCC announced that it is not allowed to create more electromagnetic spectrum pollution, there has been an increasing interest in electromagnetic compatibility in electrical systems. Chip and system design engineers have complied with automotive/FCC certification guidelines to reduce electromagnetic emissions from electronic systems without compromising performance.

2.2 EMC testing requirements for digital products

The most common electromagnetic compatibility (EMC) testing requirements for electrical products sold in the US and Europe are generally consistent for products that use Bluetooth connectivity and products that do not use Bluetooth connectivity. In addition, microcontroller-based automotive and non-automotive applications adhere to the same requirements. This level of detection varies depending on the type of product.

2.3 EMC Inspection Software

The Society of Automotive Engineers (SAE) has developed a test method that uses a standard test board to measure the electromagnetic radiation of a chip mounted on a board. The combination of the EMC test board and inspection software can also be used to perform FCC inspections.

3.0 Underwriters Laboratories Requirements (UL)

The UL 1998 standard was issued as a military or automotive quality/reliability document.

An important requirement is to analyze potential risks and implement a tracking process that tracks the software development cycle to take steps to address these risks. Another important requirement of UL 1998 is the testing of the software development cycle throughout the process. In addition to the tests typically used for software development and post-issue testing, the standard also requires failure mode and pressure detection. When reviewing the product to verify compliance with the standard, submit the test plan and test results to demonstrate compliance with the standard.

When a microcontroller becomes a critical control element of an electrical system, it should include key architecture, hardware/software features to meet the security/detection requirements set by the regulatory agency. These requirements must meet the minimum overhead requirements of the software/hardware.

Requirements for microcontrollers include:

The device architecture MUST ensure that all instructions are executed outside of program memory; this program memory contains application software and security/diagnostic software. Any modifications to these instructions must require planned external work.

Since the software in the microcontroller program memory plays an important role in the operation of the device, the instruction set MUST contain an instruction to allow the checksum and CRC calculations to be performed during runtime.

Single-chip hardware management features such as monitors (watchdogs) and "power reduction" probes provide an extra level of protection.

The port structure should be able to detect port open and insufficient ports without special programming. Each I/O pin can be set to both the output and input addresses to provide efficient and fast diagnostics.

Figure 1. I/O diagram

4.0 Automotive Quality / Safety Requirements

Existing non-Bluetooth microcontrollers are shipping in large quantities to supply safety critical automotive applications that require high levels of safety and quality.

In addition, automakers have proposed some quality/reliability requirements for microcontroller suppliers. These important areas include:

Scan Detection - Ensures that all transistors are functioning properly (up to 99% or more).

Electrical Stress Detection - Detects equipment at voltages above the specified maximum operating voltage but below the device breakdown voltage.

Built-in self-test (BIST) - reverse the encoding

Repeat tests for different single-chip functional tests and customer-specific tests.

Maverick Component Inspection - A device that eliminates distortion. Therefore, the performance of each device should be consistent when shipped.

5.0 Add Bluetooth connectivity in automotive applications

5.1 Bluetooth software

The Bluetooth specification defines the power management modes that may be involved when the device is not communicating effectively. These modes can be used to implement various power reduction strategies such as reducing or suspending the CPU clock, turning off external devices, or turning off the radio transceiver. These mechanisms reduce internal switching currents with the effect of reducing power consumption and reducing EMI. The power consumption of Bluetooth wireless devices is a major component of the overall power consumption of the Bluetooth chipset. The power management mode can also be used to keep the wireless device in full power state only when needed. (The 802.11b system is somewhat different from the one in which the wireless device in the system is always powered up, close to the power consumption of the connected LAN.)

5.2 Bluetooth hardware

Qualified microcontrollers in automotive applications now offer integrated Bluetooth support (referred to as Bluetooth baseband hardware and protocol stack software). This provides the benefits of low risk, fast track for developing products that meet automotive industry standards.

5.3 Built-in RF detection mode

The Bluetooth protocol stack provides a built-in detection mode for RF detection. There are two ways to enter Bluetooth detection mode:

Static Method - The Bluetooth core is initialized when the Detect Mode option is enabled, so it is in Detect mode when it is started.

Dynamic Method - The application software sends a command that causes the Bluetooth stack to enter detection mode. The final application can trigger this mode. For example, the application can read a switch or button.

5.4 Testing / Identification

To help embedded Bluetooth products pass authentication, vendors of Bluetooth solutions are expected to offer a full set of embedded Bluetooth stacks running on baseband processors and Bluetooth wireless devices as pre-test/pre-authentication components.

To qualify, the component must be integrated into the final product or reference design and then passed through a minimal set of tests (as described in Bluetooth's Qualification Program Reference Document).

In addition, this reference design board needs to be improved to comply with FCC and automotive EMC/EMS requirements. This means that the developer of the final product does not have to perform all of the inspection processes, and pre-test components and final product identification typically perform such inspections. Identifying/detecting individual Bluetooth components and incorporating reference designs for these components is helpful to product developers, providing them with a reliable starting point for product development and qualification.

6.0 Duplicate requirements between management agencies

Table 1. EMC Inspection Requirements

Table 2. RF detection requirements

Table 3. Detection hardware/software

Table 4. Software quality, error recovery, and diagnostics

7.0 Bluetooth Processor (Microcontroller) Example

The CP3BT1x device from National Semiconductor is an example of an automotive-grade microcontroller that uses Bluetooth connectivity. The CPU uses the latest version of the CompactRISC processor core, a high-performance 16-bit processor designed with 32-bit extensions for embedded control and connectivity applications. In addition, the CP3BT1x device offers the following features:

256KB Flash Program Memory 8KB Flash Data Memory 10KB SRAM
USB 1.1 (CP3BT10) or CAN 2.0B (CP3BT13) interface UART
SPI/Microwire interface ACCESS bus interface (I2C compatible)
Codec interface with control and capture registers for timer 37 (CP3BT10) or 40 (CP3BT13) GPIO pin 100-pin LQFP and 48-pin chip scale (7 × 7 mm) package power/performance ratio is 0.5 mA/MHz .
Very low power consumption (frequency 12 MHz, current is only 6 mA at 2.5V)
The 12 MHz operating frequency (up to 24 MHz on a single chip) provides enough CPU bandwidth to run the Bluetooth protocol stack and application tasks.

National Semiconductor offers a complete pre-test/pre-qualification Bluetooth stack that includes low-level and high-level protocol layers. This complete stack execution provides sufficient chip program memory for the application code. National Semiconductor provides one-stop application support for all aspects of the technology, including: chips, development tools, embedded Bluetooth software, and the μC/OS-II operating system.

8.0 Summary

The benefits of connecting automotive electronics to a local Bluetooth network are becoming increasingly apparent and quickly become a standard feature favored by customers with intent to purchase. However, the automotive industry has special requirements for reliability and compatibility that exceed normal home and office standards. The introduction of new wireless technologies has created new possibilities for interacting with complex systems, so the importance of ensuring non-interfering detection standards is becoming increasingly important. Qualified microcontrollers in automotive applications now offer integrated Bluetooth hardware and wireless products that offer low-risk, fast-track benefits for developing products that meet automotive industry standards.

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