I2CINIT

Action

Initializes the SCL and SDA pins.

Syntax

I2CINIT

I2CINIT twi

I2CINIT #const

Remarks

By default the SCL and SDA pins are in the right state when you reset the chip. Both the PORT and the DDR bits are set to 0 in that case.

When you need to change the DDR and/or PORT bits you can use I2CINIT to bring the pins in the proper state again.

For the XMEGA which has multiple TWI interfaces you can use a channel to specify the TWI interface otherwise the default TWIC will be used.

For normal AVR processors with multiple TWI interfaces you can specify the interface : TWI or TWI1.

When no parameter is provided, the first default TWI will be selected.

ASM

The I2C routines are located in i2c.lib. _i2c_init is called.

Example

Config Sda = Portb.5

Config Scl = Portb.7

I2cinit

Dim X As Byte , Slave As Byte

X = 0 'reset variable

Slave = &H40 'slave address of a PCF 8574 I/O IC

I2creceive Slave , X 'get the value

Print X 'print it

Example XMEGA

Open "twic" For Binary As #4 ' or use TWID,TWIE oR TWIF

Config TwiC = 100000 'CONFIG TWI will ENABLE the TWI master interface

I2cinit #4

Example Mega328PB

'--------------------------------------------------------------------------------
'name : m328pb.bas
'copyright : (c) 1995-2021, MCS Electronics
'purpose : demonstrates M328pb
'micro : Mega328pb
'suited for demo : yes
'commercial addon needed : no
'--------------------------------------------------------------------------------
$regfile = "m328pbdef.dat"
$crystal = 8000000
$baud = 19200
$hwstack = 40
$swstack = 40
$framesize = 40

' USART TX RX
' 0 D.1 D.0
' 1 B.3 B.4

' ISP programming
' MOSI-PB3 MISO-PB4 SCK-PB5

' TWI SDA SCL
' 0 C.4 C.5
' 1 E.0 E.1

'Configuration

Config Clockdiv = 1 'make sure we get 8 Mhz from internal osc

Config Com1 = Dummy , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0
Config Com2 = 19200 , Synchrone = 0 , Parity = None , Stopbits = 1 , Databits = 8 , Clockpol = 0

'we have 2 TWI interfaces
Config Scl = Portc.5 ' we need to provide the SCL pin name
Config Sda = Portc.4 ' we need to provide the SDA pin name

Config Sda1 = Porte.0 'use this for the second TWI
Config Scl1 = Porte.1

Config Twi = 100000 'speed 100 KHz
Config Twi1 = 100000 'speed 100 KHz

'some constants for the signature row
Const Device_signature_byte1 = 0
Const Device_signature_byte2 = 2
Const Device_signature_byte3 = 4

Const Rc_oscillator_calibration = 1

Const Serial_number_byte0 = &H0E
Const Serial_number_byte1 = &H0F
Const Serial_number_byte2 = &H10
Const Serial_number_byte3 = &H11
Const Serial_number_byte4 = &H12
Const Serial_number_byte5 = &H13
Const Serial_number_byte6 = &H14
Const Serial_number_byte7 = &H15
Const Serial_number_byte8 = &H16
Const Serial_number_byte9 = &H17

$lib "I2C_TWI-MULTI.lib" 'important for using 2 TWI interfaces

Dim _i2cchannel As Byte ' you MUST dim this variable yourself when using the above lib
Dim B As Byte 'just a used byte

I2cinit 'default TWI init
I2cinit Twi1 'optional specify TWI1 to init that interface

Open "com2:" For Binary As #2 'create a channel to reference the UART

'print the chip ID
Print "ID : " ; Hex(readsig(device_signature_byte1)) ; Hex(readsig(device_signature_byte2)) ; Hex(readsig(device_signature_byte3))

'all I2C statements will work the same. All you need to do is to set the _i2cchannel variable to 0 or 1
_i2cchannel = 1 'try the second bus

Print "Scan start"
For B = 0 To 254 Step 2 'for all odd addresses
I2cstart
I2cwbyte B 'send address
If Err = 0 Then 'we got an ack
Print "Slave at : " ; B ; " hex : " ; Hex(b) ; " bin : " ; Bin(b)
End If
I2cstop 'free bus
Next

Do
Print "COM1"
Print #2 , "COM2"
Waitms 1000
Loop