Action

Compiler directive that overrides the internal I2C delay routine.

 

 

Syntax

CONFIG I2CDELAY = value

 

 

Remarks

 

For the I2C routines the clock rate is calculated depending on the used crystal. In order to make it work for all I2C devices the slow mode is used. When you have faster I2C devices you can specify a low value.

 

By default a value of 5 is used. This will give a 200 kHZ clock.

When you specify 10, 10 uS will be used resulting in a 100 KHz clock.

 

When you use a very low crystal frequency, it is not possible to work with high clock frequencies.

 

ASM

The I2C routines are located in the i2c.lib/i2c.lbx files.

For chips that have hardware TWI, you can use the MasterTWI lib.

 

 

See also

CONFIG SCL , CONFIG SDA

 

 

Example

'-----------------------------------------------------------------------------------------

'name                     : i2c.bas

'copyright                : (c) 1995-2005, MCS Electronics

'purpose                  : demo: I2CSEND and I2CRECEIVE

'micro                    : Mega48

'suited for demo          : yes

'commercial addon needed  : no

'-----------------------------------------------------------------------------------------

 

$regfile = "m48def.dat"                                   ' specify the used micro

$crystal = 4000000                                         ' used crystal frequency

$baud = 19200                                               ' use baud rate

$hwstack = 32                                               ' default use 32 for the hardware stack

$swstack = 10                                               ' default use 10 for the SW stack

$framesize = 40                                             ' default use 40 for the frame space

 

Config Scl = Portb.4

Config Sda = Portb.5

 

Declare Sub Write_eeprom(byval Adres As Byte , Byval Value As Byte)

Declare Sub Read_eeprom(byval Adres As Byte , Value As Byte)

 

Const Addressw = 174                                       'slave write address

Const Addressr = 175                                       'slave read address

 

Dim B1 As Byte , Adres As Byte , Value As Byte             'dim byte

 

Call Write_eeprom(1 , 3)                                   'write value of three to address 1 of EEPROM

 

 

Call Read_eeprom(1 , Value) : Print Value                   'read it back

Call Read_eeprom(5 , Value) : Print Value                   'again for address 5

 

 

'-------- now write to a PCF8474 I/O expander -------

I2csend &H40 , 255                                         'all outputs high

I2creceive &H40 , B1                                       'retrieve input

Print "Received data " ; B1                                 'print it

End

 

Rem Note That The Slaveaddress Is Adjusted Automaticly With I2csend & I2creceive

Rem This Means You Can Specify The Baseaddress Of The Chip.

 

 

 

 

'sample of writing a byte to EEPROM AT2404

Sub Write_eeprom(byval Adres As Byte , Byval Value As Byte)

  I2cstart                                               'start condition

  I2cwbyte Addressw                                       'slave address

  I2cwbyte Adres                                         'asdress of EEPROM

  I2cwbyte Value                                         'value to write

  I2cstop                                               'stop condition

  Waitms 10                                               'wait for 10 milliseconds

End Sub

 

 

'sample of reading a byte from EEPROM AT2404

Sub Read_eeprom(byval Adres As Byte , Value As Byte)

I2cstart                                               'generate start

I2cwbyte Addressw                                       'slave adsress

I2cwbyte Adres                                           'address of EEPROM

I2cstart                                               'repeated start

I2cwbyte Addressr                                       'slave address (read)

I2crbyte Value , Nack                                   'read byte

I2cstop                                                 'generate stop

End Sub

 

 

' when you want to control a chip with a larger memory like the 24c64 it requires an additional byte

' to be sent (consult the datasheet):

' Wires from the I2C address that are not connected will default to 0 in most cases!

 

'   I2cstart                                                'start condition

'   I2cwbyte &B1010_0000                                    'slave address

'   I2cwbyte H                                              'high address

'   I2cwbyte L                                              'low address

'   I2cwbyte Value                                          'value to write

'   I2cstop                                                 'stop condition

'   Waitms 10