CXPI Click

How does it work?

CXPI Click is based on the BD41000AFJ-C, a transceiver for the Clock Extension Peripheral Interface (CXPI) communication from Rohm Semiconductor. The BD41000FJ-C is compliant with the CXPI standard established by JSAE (Society of Automotive Engineers of Japan), enabling highly responsive, reliable multiplex communication even in HMI systems, reducing vehicle weight and contributing to greater fuel efficiency. The BD41000AFJ-C operates from 7V to 18V external power supply labeled as BAT, and has several operating modes each controlled by the CS pin of the mikroBUS™, BUS pin, and UART TX pin.

It has built-in Power-OFF, Through, RX Through other than CODEC Mode for power saving control. Power-OFF Mode reduces power consumption by not supplying power to any circuits other than necessary ones for Wake-Up pulse detection (BUS) and Wake-Up input detection (TX). Through Mode does not process Coding/Decoding. It only drives signals from UART TX to BUS and from BUS to UART RX directly. RX Through Mode reverses RX output at each rising edge of BUS. CODEC Mode is the mode of CXPI communication. CS pin of the mikroBUS™ socket labeled as EN should be set high for the chip to enter CODEC Mode.

The BD41000AFJ-C can achieve a quiescent current of 3uA (typ.), ensuring suitability with automotive applications. As a result, the battery load is minimized during non-operation, contributing to higher energy savings. Also, high ESD resistance (±8kV) makes it possible to achieve low-power, high-reliability CXPI communication. Besides, it has built-in fail-safe functions that suspend the output data upon detection of under-voltage or temperature abnormality.

CXPI Click communicates with MCU using the UART interface with a transmission speed range from 5kbps to 20kbps, and commonly used UART RX and TX pins for the data transfer. Also, it has three jumpers that allow the selection of CXPI transmitter mode on the MS pin of the BD41000AFJ-C to its appropriate position marked as Master or Slave. This can be performed by using the SMD jumpers labeled as MODE. Note that all the jumpers must be placed to the same side, or else the Click board™ may become unresponsive.

This Click board™ is designed to be operated with both 3.3V and 5V logic voltage levels that can be selected via VCC SEL jumper. This allows for both 3.3V and 5V capable MCUs to use the UART communication lines properly. However, the Click board™ comes equipped with a library that contains easy to use functions and an example code that can be used as a reference for further development.

Specifications

Pinout diagram

This table shows how the pinout on CXPI Click corresponds to the pinout on the mikroBUS™ socket (the latter shown in the two middle columns).

Notes	Pin					Pin	Notes
	NC	1	AN	PWM	16	PWM	Master Mode: Clock Input
	NC	2	RST	INT	15	INT	Slave Mode: Clock Output
Enable	EN	3	CS	RX	14	TX	UART TX
	NC	4	SCK	TX	13	RX	UART RX
	NC	5	MISO	SCL	12	NC
	NC	6	MOSI	SDA	11	NC
Power Supply	3.3V	7	3.3V	5V	10	5V	Power Supply
Ground	GND	8	GND	GND	9	GND	Ground

Onboard settings and indicators

CXPI Click electrical specifications

Software Support

We provide a library for the CXPI Click on our LibStock page, as well as a demo application (example), developed using MikroElektronika compilers. The demo can run on all the main MikroElektronika development boards.

Library Description

The library covers all the necessary functions to control CXPI click board. Library performs a standard UART communication.

Key functions:

• void cxpi_write_byte ( uint8_t input ) – Write Single Byte.
• uint8_t cxpi_read_byte ( void ) – Read Single Byte.
• uint8_t cxpi_byte_ready ( void ) – Check for new byte received.

Examples description

The application is composed of three sections :

• System Initialization – Initializes UART used for communication and another UART bus used for data logging.
• Application Initialization – Initializes UART driver. In addition to this module is placed inside transmitter/receiver working mode cappable of transmission/receive the data.
• Application Task – (code snippet) – This is an example that demonstrates the use of the CXPI Click board. Transmitter/Receiver task depend on uncommented code Receiver logging each received byte to the UART for data logging, while transmitted send messages every 5 seconds.

void application_task ( )
{
    if ( app_mode == APP_MODE_TRANSMITER )
    {
        mikrobus_logWrite( "----------------------", _LOG_LINE );
        mikrobus_logWrite( "", _LOG_LINE );

        cxpi_write_data( &demo_message_data[ 0 ], 9 );

        mikrobus_logWrite( "  TX Data:  ", _LOG_TEXT );
        mikrobus_logWrite( demo_message_data, _LOG_LINE );
        Delay_ms( 5000 );
    }
}

The full application code, and ready to use projects can be found on our LibStock page.

Other mikroE Libraries used in the example:

• UART

Additional notes and informations

Depending on the development board you are using, you may need USB UART click, USB UART 2 click or RS232 click to connect to your PC, for development systems with no UART to USB interface available on the board. The terminal available in all MikroElektronika compilers, or any other terminal application of your choice, can be used to read the message.

mikroSDK

This Click board™ is supported with mikroSDK – MikroElektronika Software Development Kit. To ensure proper operation of mikroSDK compliant Click board™ demo applications, mikroSDK should be downloaded from the LibStock and installed for the compiler you are using.

For more information about mikroSDK, visit the official page.