User manual

5. Send the write disabled command (write protection) to prevent any

unwanted parameter change.

NOTE: To prevent any data corruption or loss after modifying a parameter or a

firmware update, the module must be in the ready state before shutting it

down or doing a hard reset.

5.2. I2C Interface

The I2C interface on the SPI board is a direct link to the receiver and source

modules. For the moment, only the temperature sensor is accessible. Refer to the

LM75BIMM-3/NOPB temperature sensor datasheet from Texas Instrument.

The I2C interface available with the enhance board is a port connected to MCU but

not implemented for the moment.

5.3. USB Interface

The USB interface available with the USB, CAN and SERIAL board is a VCP (virtual

COM port) serial emulation port. This port is used as a serial link with the Modbus

protocol (refer to section 5.4 Serial Link Interface). This interface can also be used

to update the USB, CAN and SERIAL board firmware in the bootloader mode.

5.4. Serial Link Interface

The serial links can be of the following electric signals: TTL, RS-232, RS-422, and

RS-485.

The serial link ports use the Modbus protocol using the RTU transmission mode only.

This section describes the commands that are implemented.

For more information on the Modbus protocol, please visit

www.modbus.org.

Read input register (function code 0x4)

The following table presents the registers for the read input commands

Table 23: Read input register messages

Address

Description

Detection status for polling mode: