REFERENCE DESIGN
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Integrating LIN Bus +Bluetooth®LE with Minimal
System Cost and Energy
Consumption - Reference
DesignTND6442/D
Motivation

Local Interconnect Network (LIN) has reached already over
20 years since its first version 1.3 was fully implemented in a vehicle.
Even though it cannot provide speeds higher than 20 kbps and single
frame is limited to 8 bytes, car manufactures still rely on it inconventional car body application such as side mirrors, wipers, ora trunk. More innovative application based on LIN is Passive Entry
Passive Start (PEPS) also found under numerous other acronyms suchas Passive Keyless Entry (PKE) or Phone−as−a−Key (PaaK).
Predominant wireless communication protocol in this case isnowadays Bluetooth Low Energy (BLE) as it can fit into a constrained
power budget imposed by limited car battery capacity. In this article
we demonstrate an optimized design for automotive keyless entry
based on LIN and BLE products of onsemi.
LIN TransceiverIn this design we use automotive−qualified NCV7428 System Basis
Chip (SBC). We select the variant with 3.3 V internal LDO voltageregulator which is capable of supplying and protecting loads of up to70 mA. Its control logic implements a 6−state−machine controlled
mainly by TxD and EN pins. Provided application diagram in thedatasheet is sufficient to implement LIN bus between any 3.3 or 5 VMCU.
BLE Transceiver

onsemi’s state−of−art BLE 5.2 automotive System−on−Chip (SoC)
NCV−RSL15 is an optimal solution for car access application due toits security features and cryptographic hardware accelerators.
Moreover, it offers LIN library as part of the official sample codepackage.
The previous generation BLE5.0 SoC NCV−RSL10 shares the same
PHY layer of BLE stack as the RSL15. RSL10’s radio front−end
supports 1 Mbps and high−speed 2 Mbps data−rate. RSL15 added
support for long range−low data rate CODED transmission. Suchdevice is an optimal solution for applications such as tire pressure
monitoring (TPMS).
Both devices offer certified BLE stack and AEC−Q100 Grade 2
which guarantees operational temperature up to 105°C.
Most importantly RSL10 and RSL15 perform best−in−classaccording to the Ultra−Low Power (ULP) efficiency benchmark
EEMBC ULPMark−CP score and RSL15 takes seconds place as per
ULPMARK−CM.
For full description of supported features visit onsemi website anddownload the documentation.
© Semiconductor Components Industries, LLC, 2015

November, 2023 − Rev. 0

1Figure 1. Testbench Photo

Key Features
NVC7428• LIN transceiver (LIN2.x and J2602compliant)• Max. 28 V supply input, 45 V abs.
Max rating• 3.3 or 5 V regulator output (LDO), 70 mA+/−2%• Protection mechanisms• Control logic with state−machine (SBC)• Low−power modes allowing Energy−saving
mechanisms• UART interface• 19.2 kbps LIN data rate
NCV−RSL15• Arm Cortex M33• Cyber−security features• Localization features• Certified BLE 5.2• 512 kB Flash• AEC−Q100 Grade 2 (−40 + 105°C)
NCV−RSL10• Arm Cortex M3• AES128 Hardware−accelerated engine• Certified BLE 5.0• 384 kB Flash• AEC−Q100 Grade 2

Publication Order Number:
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Figure 2. Testbench Block Diagram
HW and SW Demonstrator

RSL15. We use the existing LIN sample code for RSL15
device that can be added in the onsemi IDE from the CMSIS
example library.
In case of RSL10, we write a custom LIN protocol in theapplication program that uses the UART as an underlying
communication mechanism. In effect we can achieve
20 kbps data−rate purely in our custom test program writtenfrom scratch. Refer to Appendix for the graphicaldescription of the application.

The basic physical principle of the demonstrator can beseen on Figure 2 We use following apparatus in our setup:• BLE Evaluation Boards and LIN Interfaces withcabling• External Power Supply Generator• Oscilloscope
Apart from the physical setup presented on Figure 3 andFigure 4 we need separate test program for RSL10 andFigure 4. RSL10 LIN Setup

Figure 3. RSL15 LIN Setup

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LIN BUS PRINCIPLES
Dominant state (0 V) has the power to overwrite therecessive default LIN bus state (12 V). This can be observedin Figure 6 where a packet is put on the bus that by default
is pulled up to the 12 V. This voltage is common in
automotive body applications.
Packet information is encoded on the bus by pulling theLIN data signal down (bit 0) or pulling up (bit 1).
Transceiver does this using its internal push−pull circuit
connected directly to LIN data pin. See Block Diagram of
NCV7428 for reference. The logical state of the LIN bus isdetermined by comparing the bus voltage to the thresholdvoltage reference. For LIN communication 40% or less of
12 V (<= 4.8 V) corresponds to logical 0. 60% or more(>= 7.2 V) is logical 1.

Values of the passive components are taken from thedatasheet.
Table 3. PIN ASSIGNMENT
Role \CompDREVDPU_RPU_

CLIN_LIN

LIN

M/SMasterSlave

CVS

RPU_- CVOUT
RSTN

N/A

1N41481 kΩ

1 nF

100 nF N/A

2 mF

N/A−−220 pF 100 nF N/A

2 mF

Figure 5. LIN Packet Definition

Figure 7. RSL10 Evaluation Board Supply
Setting− EXT Regulated

Figure 6. Recorded LIN Packet

After configuring the power supply according to Table 2
we can plug VOUT and GND from NCV7428 into
EXTERNAL POWER socket. The remaining signals
coming from the transceiver are TX, RX, EN. Follow Tablefor reference.
RSL15 Evaluation Board power supply configuration ismuch simpler− VBAT−SEL jumper should connect VBATwith VOUT. As shown on Figure 3 RSL15 LIN Setup theVOUT pin of NCV7428 supplying 3.3 V is connected toVBAT header on the board.
Application diagram of the LIN transceiver should befollowed when building the interface between 12 V and
3.3 V net. It advises on which external components should
be used for the controller (master) and peripheral (slave). In
this design 2 slaves and 1 master were tested.

Table 1. PIN ASSIGNMENTSignal \ Pin

RSL15 GPIORSL10 GPIOTX

23RX

31EN

44Button

55In next steps RSL10 and RSL15 LIN implementation ispresented interchangeably. Due to higher complexity ofRSL10 Evaluation Board and the custom LIN driverdeveloped for demonstration we focus on this device interms of SW and HW.
Table 2. RSL10 EXTERNAL SUPPLYCONFIGURATION
Mode \ Config

VDD_AT

VDDO

3.3 V

VBAT

EXT Regulated(Figure 6)

VDDO

3.3 V

REG

3.3 V

EXT VBAT

VDDO

VBAT

REG

BATT

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In below figures we observe signals on the LIN master
controller in 3 timespans:• “Request−Response”− initial transmission and response
in 1 figure,• “Request”− packet transmission from the master,• “Response”− packet received from the slave.

Figure 8. NCV7428 Interface−Peripheral
Board− Slave

It is advised that the device and the whole setup is handledvery carefully when switching 12 V power supply on/off
and reconnecting any pin either on the Evaluation Board oron the LIN interface. Also connecting probes ofa measurement device might lead to a short−circuit such as
12 V LIN line with GND which damages NCV7428
irreversibility.

Figure 10. LIN Master Request Response: UART
TX, RX and LIN Data

RSL10 REQUEST RESPONSE SAMPLE CODE
The application demonstrated in Appendix section:
Figure 21 and Figure 22, utilizes two modes of NCV7428:
Standby and Normal. The transition is done upon EN andTxD input signal.

Figure 11. Master Request (Left) Response (Right):
UART TX, EN and LIN Data

Figure 9. Part of NCV7428 State Machine

LIN MASTER
In total, 4 signals can be monitored on the oscilloscope todiagnose the LIN bus: TX, RX, EN logic signal of NCV7428
and LIN data signal.
• Top, yellow − TxD*,• Middle, green − RxD* or EN,• Bottom, red − LIN data.
* Disregard “Slave” prefix in below Figures.
Figure 12. LIN Master, Request: TX Frame in
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Figure 16. RSL15 Slave Application Sequence

To use the driver, we initialize it differently for slave andmaster in our common application.

Figure 13. LIN Master, Response from Slave: RX
Frame in Close−up#ifdef LIN_CONTROLLER
lin->Initialize(Controller_CallBack,uart);lin->Control(ARM_LIN_CONTROL_MODE,
ARM_LIN_MODE_CONTROLLER);#else
lin->Initialize(Peripheral_CallBack,uart);#endif.

LIN SLAVE
In the below figures we record the bus traffic at the slave’s
transceiver which contains both request and response LIN
packet in one continuous capture.

In the inifinite loop in the main program we invoke thetransfer function that fills and empties the TX and RX buffer.
while (1){lin->CheckTransferDone();
LIN_CheckForErrors();#ifndef LIN_CONTROLLER
lin->Transfer(lin_tx_buffer,
lin_rx_buffer, APP_LIN_RX_BUFFER_MAX_SIZE);#endif
SYS_WATCHDOG_REFRESH();__WFI();}

Figure 14. LIN Slave, Received Request,Transmitted Response: UART TX, RX, LIN Data

The demonstrator blinks an LED if:• Master has successfully transmitted a packet• Slave has successfully received the packet and its
content matches the expected value.

Figure 15. LIN Slave, Received Request (Left),
Transmitted Response (Right): UART TX, EN, LIN
Data

RSL15 SINGLE BROADCAST SAMPLE CODE
LIN driver is added in the RTE configuration by checkingthe box as shown below.

Figure 17. RSL15 Master Application Sequence

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The same packet is seen by the slave after thecommunication delay.

Figure 18. RSL15 Slave Application Sequence

In our application the transmitted packet is immediately
received back (loop−back) by the sender. Therefore, theTxD and RxD line are identical at the sender’s NCV7428. It
is important that this does not lead to a side−effect such asprocessing by the controller of its own packet.

Figure 20. LIN Slave RX Message: UART RX, TX andLIN DataUsing onsemi’s NCV7428 brings cost and size benefits
for the end application. Thanks to our software sample codeand testbench we demonstrated how to efficiently control
LIN bus through a request−response scheme that we
implemented and programmed on RSL10 and RSL15
boards.

Figure 19. LIN Master TX Message: UART RX, TX andLIN Data

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APPENDIX 1

Figure 21. RSL10 Master Application Diagram

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APPENDIX 2

Figure 22. RSL10 Slave Application Diagram

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