I2C_TWI-MULTI

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The I2C_TWI-MULTI library is intended to be used with normal AVR processors which have 2 or more TWI interfaces.

An example of such a processor is the ATMEGA328PB

 

In order to support multiple busses, this library need to be included using the $LIB directive.

Further you need to create a byte variable named _i2cchannel in your code.

 

This variable will hold the bus or TWI number.

By default it will be 0 and thus the usual TWI hardware will be used :  Portc.5  and  Portc.4

 

By setting the variable to 1, the second TWI hardware will be used :   Porte.0  and Porte.1

 

Further you need to use CONFIG TWI1 instead of CONFIG TWI in order to specify the clock rate for the second TWI : Config Twi1 = 100000

 

All other code will remain compatible.

 

Example

 

'--------------------------------------------------------------------------------
'name                     : m328pb.bas
'copyright                : (c) 1995-2016, 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