MPUs and MCUs
band. The 3 V to 42 V input voltage range of the LT8602 makes the device ideal for automotive applications, which must regulate through cold crank and start stop scenarios with minimum input voltages as low as 3 V and load dump transients more than 40 V. Figure 3 shows an alternative system block diagram with connectors, a reduced set of peripherals, and one automotive qualified connector carrying all relevant signals. This configuration allows the design of a smaller form factor board.
This system solution results in a reduced system bill of materials (BOM) cost because the ADSP-BF706 acts as a microcontroller and an audio processor.
For full details on the solution, see the EVWSS v1 Demo Manual and the EVWSS v2 Demo Manual, which are provided in the software download package. This software package (EVWSS-BF_SRC-Rel2.0.0) is available by request from the Software Request Form page on the Analog Devices website. For full details on the ADSP-BF706, see the ADSP-BF70x Blackfin+ Processory Hardware Reference and the ADSP-BF7xx Blackfin+ Processor Programming Reference. The EVWSS software architecture is based on the ADSP-BF706 hardware architecture. The processor dependence on the hardware architecture is due to the memory mapped SPI. The CAN interface reads directly from the flash memory using memory mapped SPI. This feature reduces the complexity of the EVWSS library and makes the memory access efficient for warning sound generation.
Software Components
The EVWSS software architecture consists of the components shown in Figure 4. This section details the software components. The SPORT callback feature maps to the audio data sample rate and runs in the SPORT transceiver interrupt service routine (ISR) context, reading flash files (SPI memory mapped), performing audio manipulation using the EVWSS library, and sending out modified audio on the SPORT transceiver interface. The EVWSS library holds the different functions to synthesize the warning sound. The EVWSS library also receives vehicle speed input from the CAN stack (or the universal asynchronous receiver and transmitter (UART) interface for debugging). The TDA7803 driver controls the external power amplifier to generate the warning sound. The EVWSS application framework configures the system peripherals, CAN stack, and the TDA7803 driver.
EVWSS Library Functions The following sections describe the functions
www.cieonline.co.uk
of the EVWSS library. For full details, see the Electronic Vehicle Warning Sound System Release Notes, which can be found in the software download package.
Pitch shifting is the concept of shifting the spectrum of the audio signal based on a control input. In the EVWSS application, the base pitch of the WAV file is shifted depending on the vehicle speed input. The engine sound is dependent on the engine strokes, which include intake, compression, power (expansion), and exhaust. These strokes create frequency modulated tones instead of just pure tones. Vary the pitch shift parameter across the samples to achieve frequency modulation. Two kinds of modulation (sawtooth and triangular) are included in this application. In sawtooth modulation, the frequency ramps from lowest to highest and then back to lowest with a jump. In triangular modulation, the frequency ramps from lowest to highest and then ramps back down to lowest. For audio mixing, configure the various gains with respect to vehicle speed. Although the required WAV files are present in flash, the user can play or stop some of the WAV files, depending on the dynamic conditions.
SigmaDSP-Based Solution For entry-level applications, an ADAU1450 SigmaDSP processor can be used as an alternative to the ADSP-BF706 processor. For evaluation purposes, the EVAL-ADAU1452 evaluation board can be used.
Figure 5 shows the different processing blocks inside the SigmaDSP processor. The following software requirements are supported in the ADAU1450 using the SigmaStudio programming environment: • Multiple tone generation • Dynamic volume control with up to 64 ranges
• Sound mixing • Limiter • Pitch shifting that increases audio pitch as speed increases
• Simultaneous playback of up to 5 WAV files from the SPI flash memory
Analog Devices provides an engine sound simulator module in SigmaStudio to simplify engine sound tuning and reduce the number of external, simultaneous WAV files required. The engine sound simulator can internally generate up to 32 harmonics. The order and amplitude of these harmonics can be programmed through the graphical user interface (GUI).
The harmonic generator module is available as part of the ESS Toolbox. It can be downloaded directly from the SigmaStudio
Figure 5. Processing blocks on SigmaDSP processor Components in Electronics April 2021 31
Figure 4. EVWSS software architecture block diagram
download page (Rev 4.4. upward). Note that SigmaStudio cannot support a CAN software stack, and an external microprocessor is required.
SigmaStudio
SigmaStudio is a graphical programming environment originally designed for the SigmaDSP portfolio of processors. This software has a built-in library of algorithms developed specifically for automotive applications. The GUI simplifies the tuning process and provides controls and filter coefficients that can be varied on the fly without the requirement for writing code. SigmaStudio can be
downloaded from the SigmaStudio page on the Analog Devices website.
Conclusion
Analog Devices offers comprehensive solutions for an entry-level system and for an advanced engine sound system that supports in-cabin engine sounds and external engine sounds. This article aims to ease the decision- making process for the user, as well as reduce user time to market. Analog Devices offers a complete system solution, including the necessary software components for rapid prototyping and product development.
analog.com
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54
