Ansteuerung der Porterweiterung I2C PCA9954

PASCAL-Unit fuer Ansteuerung der Porterweiterung I2C PCA9954

{==============================================================================}

unit TWI_PCA9554;

{ }

{ Unit fuer Ansteuerung der Porterweiterung I2C PCA9954 }

{ }

{ Bearbeitungsbeginn: 05.10.2010 }

{ Bearbeitungsstand : 08.10.2010 }

{ Bearbeiter : S. Taborek }

{==============================================================================}

{ }

{ Uses Hardware-TWI from Library-Manager }

{ The first Call in Main-Program have to be: Init_PCA9554(Modul-Adresse); }

{ Change the Adresse, if the Chip-address-input 0, 1, 2 ist unlike Low. }

{------------------------------------------------------------------------------}

Command Protocol Function PCA9554

0 read byte Input Port register

1 read/write byte Output Port register

2 read/write byte Polarity Inversion register

3 read/write byte Configuration register

Bit Symbol Access Value Description

7 I7 read only X determined by externally applied logic level

6 I6 read only X

5 I5 read only X

4 I4 read only X

3 I3 read only X

2 I2 read only X

1 I1 read only X

0 I0 read only X

This register reflects the outgoing logic levels of the pins defined as outputs

by Register 3. Bit values in this register have no effect on pins defined as

inputs. Reads from this register return the value that is in the flip-flop

controlling the output selection, not the actual pin value.

Legend: * default value.

Bit Symbol Access Value Description

7 O7 R 1* reflects outgoing logic levels of pins defined as

6 O6 R 1* outputs by Register 3

5 O5 R 1*

4 O4 R 1*

3 O3 R 1*

2 O2 R 1*

1 O1 R 1*

0 O0 R 1*

0 = Input Port register data retained (default value)

1 = Input Port register data inverted

Bit Symbol Access Value Description

7 N7 R/W 0* inverts polarity of Input Port register data

6 N6 R/W 0*

5 N5 R/W 0*

4 N4 R/W 0*

3 N3 R/W 0*

2 N2 R/W 0*

1 N1 R/W 0*

0 N0 R/W 0*

This register configures the directions of the I/O pins.

0 = corresponding port pin enabled as an output

1 = corresponding port pin configured as input

Legend: * default value.

Bit Symbol Access Value Description

7 C7 R/W 1* configures the directions of the I/O pins

6 C6 R/W 1*

5 C5 R/W 1*

4 C4 R/W 1*

3 C3 R/W 1*

2 C2 R/W 1*

1 C1 R/W 1*

0 C0 R/W 1*

//-----------------------------Interface-------------------------------

function Init_PCA9554(UnitAdr:Byte):byte;

function Config_PCA9554(directions, invert :byte):byte;

function Write_PCA9554(daten:byte):byte;

function Read_PCA9554(var daten:byte):byte;

//---------------------------------------------------------------------

implementation

const

Twi_clock : longint = 400000; // max 400 KHz

Read_Adr : byte = 0x01;

Write_Adr : byte = 0x00;

C_PCA9554_Adr : byte = 0x38; // Datenblatt und A2A1A0 = low

var

PCA9554_Conf : byte;

PCA9554_Adr : byte;

{------------------------------------------------------------------------------}

function Init_PCA9554(UnitAdr:Byte):byte;

{------------------------------------------------------------------------------}

{Returns 0 if OK }

{Function muss nur einmal aufgerufen werden}

begin

TWI_Init(Twi_clock);

PCA9554_Adr := (UnitAdr shl 1);

Result := 0;

if (PCA9554_Adr < C_PCA9554_Adr) then Result := 1;

end;

{------------------------------------------------------------------------------}

function Config_PCA9554(directions, invert:byte):byte;

{------------------------------------------------------------------------------}

{Returns 0 if OK }

{Function muss nur einmal aufgerufen werden}

begin

Result := 1;

if (PCA9554_Adr < C_PCA9554_Adr) then exit;

if TWI_Start() = 0 then begin // issue TWI start signal

TWI_Write(PCA9554_Adr or Write_Adr); // send byte via TWI (device address)

TWI_Write(0x02); // send byte (Invert-cmd)

TWI_Write(invert); // send data (Register2) (for input-inv)

TWI_Write(PCA9554_Adr or Write_Adr);

TWI_Write(0x03); // send byte (Direct ion-cmd)

PCA9554_Conf := directions; // merkt die aktuelle Config

TWI_Write(directions); // send data (Register3)

TWI_Stop(); // issue TWI stop signal

delay_ms(1);

Result := 0;

end;

{------------------------------------------------------------------------------}

function Write_PCA9554(daten:byte):byte;

{------------------------------------------------------------------------------}

{Returns 0 if OK }

begin

Result := 1;

if TWI_Start() = 0 then begin // issue TWI start signal

TWI_Write(PCA9554_Adr or Write_Adr); // send byte via TWI (device address + W)

TWI_Write(0x1); // send byte (Out-cmd=1)

TWI_Write(daten); // send data (Register1)

TWI_Stop(); // issue TWI stop signal

Result := 0;

end;

{------------------------------------------------------------------------------}

function Read_PCA9554(var daten:byte):byte;

{------------------------------------------------------------------------------}

{Returns 0 if OK }

begin

Result := 1;

if TWI_Start() = 0 then begin // issue TWI start signal

TWI_Write(PCA9554_Adr or Write_Adr); // send byte via TWI (device address)

TWI_Write(0x0); // send byte (Inp-cmd=0)

TWI_Start(); // issue TWI start signal

TWI_Write(PCA9554_Adr or Read_Adr); // send byte via TWI (device address + R)

daten := TWI_Read(0); // read data (Register0)

TWI_Stop(); // issue TWI stop signal

Result := 0;

end;

//------------------------------------------------------------------------------

end.