so funktionierts nun aber warum?
Master:
Code:
$regfile = "M32def.dat" ' the used chip
$crystal = 16000000 ' frequency used
$baud = 19200 ' baud rate
$lib "i2c_twi.lbx" ' we do not use software emulated I2C but the TWI
Config Scl = Portc.0 ' we need to provide the SCL pin name
Config Sda = Portc.1 ' we need to provide the SDA pin name
'On the Mega8, On the slave Mega8
'scl=PC5 , pin 28 scl=PC5 , pin 28
'sda=PC4 , pin 27 sda=PC4 , pin 27
'the M8 slave uses a simple protocol
'WRITE -> Start-address-B1-B2-STOP
'READ -> start-address-B1-B2-STOP
'start -> I2CSTART
'address-the slave address
'B1 and B2 are 2 bytes that when written, write to B1
' when read , return A/D converter value
Dim B1 As Byte , B2 As Byte
Dim W As Word At B1 Overlay
I2cinit ' we need to set the pins in the proper state
Twbr = 12 'bit rate register
Twsr = 0 'pre scaler bits
Dim B As Byte , X As Byte
Print "Mega8 TWI master demo"
Do
I2cstart
I2cwbyte &H70 ' slave address write
I2cwbyte &B10101010 ' write command
I2cwbyte 2
I2cstop
Print "Error : " ; Err ' show error status
I2cstart
I2cwbyte &H71
I2crbyte B1 , Ack
I2crbyte B2 , Nack
I2cstop
Print "Error : " ; Err ' show error
Print "received A/D : " ; W
Waitms 500 'wait a bit
Loop
End
Slave:
Code:
$regfile = "M32def.dat" ' the chip we use
$crystal = 16000000 ' crystal oscillator value
$baud = 19200 ' baud rate
$lib "i2c_twi-slave.lbx"
Print "MCS Electronics M8 TWI-slave demo"
Print "Use with M8-TWI master demo"
Config Adc = Single , Prescaler = Auto
'Now give power to the chip
Start Adc
Dim W As Word
Config Portb = Output
Dim Status As Byte 'only for debug
'Print Hex(status)
Config Twislave = &H70 , Btr = 2 , Bitrate = 100000
' ^--- slave address
' ^---------- 2 bytes to receive
' ^--- bitrate is 100 KHz
'The variables Twi , Twi_btr and Twi_btw are created by the compiler. These are all bytes
'The TWI interrupt is enabled but you need to enabled the global interrupt
Enable Interrupts
'this is just an empty loop but you could perform other tasks there
Do
'Print Getadc(0)
'Waitms 500
nop
Loop
End
'The following labels are called from the library. You need to insert code in these subroutines
'Notice that the PRINT commands are remarked.
'You can unmark them and see what happens, but it will result in occasional errors in the transmission
'The idea is that you write your code in the called labels. And this code must execute in as little time
'as possible. So when you slave must read the A/D converter, you can best do it in the main program
'then the data is available when the master needs it, and you do not need to do the conversion which cost time.
'A master can send or receive bytes.
'A master protocol can also send some bytes, then receive some bytes
'The master and slave must match.
'the following labels are called from the library when master send stop or start
Twi_stop_rstart_received:
' Print "Master sent stop or repeated start"
Return
'master sent our slave address and will not send data
Twi_addressed_goread:
' Print "We were addressed and master will send data"
Return
Twi_addressed_gowrite:
' Print "We were addressed and master will read data"
Return
'this label is called when the master sends data and the slave has received the byte
'the variable TWI holds the received value
Twi_gotdata:
' Print "received : " ; Twi ; " byte no : " ; Twi_btw
Select Case Twi_btw
Case 1 : Portb = Twi ' first byte
Case 2: 'you can set another port here for example
End Select
Return
'this label is called when the master receives data and needs a byte
'the variable twi_btr is a byte variable that holds the index of the needed byte
'so when sending multiple bytes from an array, twi_btr can be used for the index
Twi_master_needs_byte:
'Print "Master needs byte : " ; Twi_btr
Select Case Twi_btr
Case 1: ' first byte
W = 100 'in this example the conversion is done here
' but a better option would have been to just pass the value of W and do the conversion in the main loop
Twi = Low(w)
Case 2 ' send second byte
Twi = High(w)
End Select
Return
'when the mast has all bytes received this label will be called
Twi_master_need_nomore_byte:
' Print "Master does not need anymore bytes"
Return
Was bedeutet das Case 1 und 2?
wie kann ich das umschreiben damit er nur 1 Byte sendet?
wenn ich case 2 weg mache kommt wieder irgendwas raus.
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