Franck TMA engineerFranck, INTITEK-TMA Electronic Engineer, explains the fundamental principal of LIN protocol in the last generation alternator regulators.

With the increase of embedded systems in vehicles, it has become imperative to use a network enabling them to communicate with the on-board computer.

In the case of the last generations of alternators, the regulators use LIN protocol whose communication is bidirectional. That means that the on-board computer talks to the alternator which answers to it.
This is for example the case of ONYX and TITANE test benches which totally simulate the on-board computer functionalities. They are able to drive the Lin alternator, get a feedback of its information, and report all details on a ticket.

Connection TMA ONYX LIN alternator
Connection ONYX / Lin Alternator

But, what is LIN Protocol?

The Lin protocol (Local Interconnect Network) is a serial system bus used mainly in automotive industry meeting the standard ISO-17987. This is a reliable and economical communication protocol allowing vehicle’s on-board computer to converse with its subsystems.

LIN alternator regulatorThere are 2 main LIN families: LIN1 and LIN2. They are essentially differentiated by the way their messages are encoded. Those two families can generally run under two transfer speeds: 9600 or 19200 bauds.
Inside LIN protocol, we find five types (1, 2, 3, 4 and 5) each having five different versions (a, b, c, d and e). Those variants allow to systems to identify, send a feedback of issues and information or to be drove.

A communication using LIN protocol is composed of a sequence of frames representing a specific message, for example, the identification of the alternator or its diagnostic.

Example of dialogue with 2 frames :

Identification frameDiagnostic frame
Examples: regulator Id, alternator brand…Examples: breakdown, measurement…


Each frame contains information or parameters coming from the alternator or vehicle calculator. Below, examples of a diagnostic frame:

Example of a diagnostic frame for a regulator with Lin 1 Type 1 version b frame

1st byte2nd byte3rd byte4th byte

A : Overheat

B : Electrical failure

C : Mechanical failure

D : Excitation signal

E : Excitation current

F : LIN latency

G : LIN error

H : Load ramp

I : Excitation control

J : Information on 4th byte

K : Voltage regulation or speed or …

During a communication with an alternator, the car computer can   :

Ask some informationGet breakdwonSet parameters
o    Brand and model of the alternator
o    Brand and model of the regulator
o    Rotation speed
o    Excitation current
o    Temperature
o    Mechanical
o    Electrical
o    Overheat
o    Voltage regulation
o    Response time
o    Default mode (LIN breakdown)