In any vehicle, the instrument cluster forms a critical part as it is the face of the
vehicle that reflects the current state. Apart from providing the basic vehicle information, it can also provide
crucial indications of electrical component malfunctions (EFI /ISG related). Clusters can acquire vehicle data
over simple mechanisms such as encoders as well as through complex interfaces such as CAN, SAEJ1850 etc.,
Instrument cluster design for electric vehicles may have less system complexity, but they have to be more user
friendly, less power hungry, and a cost-effective solution. Careful design and choice of cluster components is
necessary to meet the stringent compliance requirements. Of the constituent components, the MCU holds the major
stock whereas only a few vendors will be supporting automotive grade with the desired feature sets.
Renesas RL78 is an ultra-low power microcontroller (MCU) that enables customers to build compact, energy
efficient instrument clusters for a wide range of two-wheeler and four-wheeler vehicles. It offers highly
suitable peripheral interfaces such as: Three Channels of Stepper Motor Controller, LCD controller,
Multiple IOs etc.,
In this blog, we will discuss in detail about the various features of an instrument cluster and how RL78 MCU will
help simplify the design.
The major components and their functionalities are as follows:
There could be variations in the offerings and feature set based on the vehicle manufacturer.
Renesas is a leading semi-conductor company in the automotive space offering cluster solutions for many decades.
While there are some architectural differences between all the MCU’s of the Renesas RL78 family, the sub-system
remains more or less the same. The high-level design of the RL78 MCU based instrument cluster is captured below:
RL78 series of MCU’s help realize vehicle clusters effectively with its feature rich peripherals set:
Microcontroller: The RL78 MCU helps in achieving the highest performance within the low end MCU
space. It offers improved efficiency, extensive scalability and reliable safety functions that aid in developing
energy efficient instrument clusters. It has an operating voltage that ranges from 2.7V to 5.5V and flashes the
program using 80 microcontroller pins.
Stepper Motor Drivers: There are up to three channels of stepper motor controllers / drivers
with zero-point detection that can be configured using PORT pins (Sin+, Sin-, Cos+, Cos-). Each channel is
controlling a stepper motor dedicated to gauges which commands the motor to move and hold at one of the angles
without any position sensor. With the help of software based PID control, it is possible to effectively control
Segment LCD Controller: Capable of driving up to 200+ segments, the in-built LCD controller is
available for controlling the segmented display with various resolutions such as 27 X 4, 39 X 4, 48 X 4, 53 X 4
and 54 X 4 which is directly driven from the RL78 microcontroller. The LCD screen can be controlled by the
software to display any kind of data dynamically such as TRPI information, hour meter data etc.
Multiple IOs: There are multiple analogs and digital IOs available for interfacing sensors and
Tell-Tale LEDs. RPM, temperature, and fuel level sensors are interfaced via a suitable front-end circuit. If
needed, various Tell-Tale LEDs such as turn left, turn right, service, brake, etc. can be driven with dedicated
Variants of RL78 also offers sound generator which can set a volume level and tone frequency, two channels of
CAN, and expanded flash memory/RAM up to a maximum of 512 KB/24 KB, suitable for low-end instrument cluster
Embien Technologies is a leading embedded systems development company that specializes in high – tech product
engineering services. We help clients take competitive lead in their markets. With a unique mix of innovation,
technology, and quality, we offer cutting-edge automotive electronics system designs by adapting the latest
technologies in clusters, diagnostics, infotainment, connectivity etc., With deep domain expertise, we have
assisted several OEMs, Tier 1, and Tier 2 vendors to surge their automotive electronics such as Instrument
Clusters (Heavy & Light- Duty Vehicles), Digital Cockpits etc., by integrating sensors & radars, network
connectivity, path planning & mapping technologies. Do you have a design idea in mind? Then, get in touch
with us today!
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In any vehicle, the instrument cluster forms a critical part as it is the face of the vehicle that reflects the current state.