I2CWrite Problem

[richard]

I2C_Address = I2C_Address +1
makes no sense at all, in pbp i2c address are 7 bits + r/w bit at bit0
so i2c write to $76 and to $77 are writes to the exact same address

I2C_Address = I2C_Address +2
will get a "NEW" address

[nuno106]

Hi Richard and thanks for the reply.

The I2C_Address = I2C_Address +1 is only to show that 16 bits of data work when I2C_Address is equal to $78, in other cases, it don't work.

Thanks,
Nuno

[richard]

still makes zero sense .

if no slave device responds with an ack then the pbp code will terminate the transaction
sending data to random or incorrect address' will achieve and prove nothing at all

what are you really doing and what is the slave device , how is connected

[tumbleweed]

if no slave device responds with an ack then the pbp code will terminate the transaction

richard's correct in that if I2CWRITE doesn't get an ACK in response to writing a byte it immediately sends a STOP and returns with the CARRY flag set.
Unfortunately, it never checks the return value so it continues on with the rest of the bytes in the I2CWRITE statement (here you have four of them).

Since it just sent a STOP, it sends a START again, the next byte in the statement (which is now treated as a slave address), gets another NACK, sends STOP, etc, etc until all the bytes are sent.

It should really terminate the entire I2CWRITE statement when it gets a NACK to the the first byte (the slave address), but it doesn't... it just erroneously continues on writing what amounts to garbage to whatever "address" it runs across.

[richard]

Unfortunately, it never checks the return value so it continues on with the rest of the bytes in the I2CWRITE statement (here you have four of them).

Not what i find . it may vary by pic18/16 and/or pbp version
i my test the transaction terminates at the first nak and is followed by a "funny start" dud transaction , the data in the sq brackets is never sent





pic18f45k80

'OSCTUNE.6 = 1 ; Enable 4x PLL
OSCCON = 110000




TRISD=000110 'set PORTD 


define OSC 16
DEFINE I2C_SLOW 1
ADR VAR BYTE
ADR2 VAR BYTE
CMD  VAR BYTE
ADR=$48
ADR2=$70   


SDA VAR PORTD.3
SCL VAR PORTD.2




CMD= $48


FEDO:
I2CWRITE SDA,SCL,ADR,[5]
I2CWRITE SDA,SCL,ADR2,CMD,[3,4]
PAUSE 250
I2CWRITE SDA,SCL,ADR,[0]
I2CWRITE SDA,SCL,ADR2,$48,[2,7]
PAUSE 250
GOTO FEDO

edit
might be a proteus artifact also, i have not scoped it

[tumbleweed]

That produces a slightly different result, but it's still wrong... there are extra transactions after getting a NACK to the first byte (slave address).
"S 02 N P" shouldn't be there, and I have a hunch that if you change "ADR2=$70" to something else you'll find that is wrong too.
I didn't bother trying to figure out exactly what it's sending, but it's not really what's in the remaining I2CWRITE statement.

I looked at the asm code in both cases and there's nothing I see to look at the ack/nack result of sending a byte, except to send a STOP and reset the internal state so the next byte starts a new transaction. There's nothing to "skip over sending the remaining bytes" in the I2CWRITE.