Short summary

Name	`I2C_PCF8574_read`
→POU type	→function
Category	more system blocks, blocks for I2C elements
Graphical interface
Available since	version 1.13.0 (for logi.CAD 3) and version 2.3.901 of logi.RTS This block is supported for →Raspberry Pi only. version 1.109.0 (for logi.CAD 3) and version 3.19.0 of logi.RTS This block is supported for Raspberry Pi and the platform `LinuxX86` only.

Functionality

The block reads the states of inputs from PCF8574 (→I2C port expanders).

For more information on the PCF8574 chip see for example: http://www.nxp.com/documents/data_sheet/PCF8574.pdf (product specification by manufacturer NXP)

Inputs, return value

	Identifier	→Data type	Description
Inputs:	`fd`	`DINT`	the handle for the I2C device file opened by the `I2C_Open` block
Inputs:	`address`	`INT`	the I2C address of the PCF8574 (port expander)
Return value:	–	`ARRAY[0..7] OF BOOL`	returns the states of the pins of the PCF8574 (port expander)

Input EN and output ENO are available when →calling the block. See "Execution control: EN, ENO" for information on input EN and output ENO.

Example for usage within ST-editor

PROGRAM Test
VAR
    handle : DINT := -1;
    digitals : ARRAY[0..7] OF BOOL;
END_VAR;
 
ENO := TRUE;
IF handle < 0 THEN
    handle := I2C_open(bus_id := 1, ENO => ENO);
ELSIF ENO THEN     
        digitals := I2C_PCF8574_read(fd := handle, address := 56, ENO => ENO);
END_IF;
END_PROGRAM

When creating your application within the ST-editor, enter a call of a block by typing the text as requested by the syntax or use Content Assist.