I2C CONFUSION, Help needed please

[FromTheCockpit]

OSCCON changed to set 4MHz, internal oscillator.
I2CSLOW 1 stays commented
I2CHOLD 1 stays commented

LED 	Var PortC.0
Value Var 	Byte
Addr	Var	Byte
Loc 	Var	Byte
'---------------------------------------------------------
Pause 500
	DEBUG "Start......",13,10
Value=0
Addr=$9B 'Tried $3B,$5B
Loc=0

Main:
High Led : Pause 500: Low Led : PAUSE 500
	I2CWRITE SDA,SCL,ADDR,LOC
	Addr=$1B
	I2CREAD SDA,SCL,ADDR,LOC,[VALUE],Fail
	PAUSE 25
	DEBUG  HEX Value,13,10
	PAUSE 250
	DEBUG "Done....",13,10
WHILE 1 : WEND
Goto Main

Fail:
	toggle portc.2
goto main

No Luck

> It is bit 7 for R/W (Slave address + write bit)

[LinkMTech]

> It is bit 7 for R/W (Slave address + write bit)

How did you find that?

[FromTheCockpit]

Picked up from the datasheet of the device. That is what I understood, am I wrong?
Though I did tried $3B & $5B.

[LinkMTech]

Not sure if you're wrong or not. I'm still trying to decipher that part in the datasheet because they don't make it easy. I've found that some information has to be gleaned from other devices of the same manufacturer to put the whole story together, kinda sucks!

I also noticed the address stays at $1B after the first loop in your test program and if it works you might miss it.

Note: I just found one of my programs on another I2C device that has bit 1=0 as the Write bit.
$1B = $00011011 used for Read
$1A = $00011010 used for Write

[FromTheCockpit]

I read it again to confirm this, the attachment is my source. It also mentions 9 bits long address. Not sure who sends an ack. I see that in read statement the device send ack, so why add it to the address PIC is sending. Very confusing.

[LinkMTech]

Ahhhh... okay
Let's use this info then. Looks like the address is using bits 1~7 and the Read/Write control bit is 0.
If control bit is set (=1) then Read, if bit cleared (=0) then Write

So:
%00110111 = $37 ' Read function
%00110110 = $36 ' Write function

Try that.

By the way, the device sends the ACK, or acknowledges, by holding the Data line LOW on the 9th clock cycle. The PIC will see this and continue to send data.

[FromTheCockpit]

By the way, the device sends the ACK, or acknowledges, by holding the Data line LOW on the 9th clock cycle. The PIC will see this and continue to send data.

How do I implement this, like this below?

Main:
High Led : Pause 500: Low Led : PAUSE 500
	Addr=$36
	I2CWRITE SDA,SCL,ADDR,LOC
	Addr=$37 : pause 10                    ' OR If SDA=1 then main 
	I2CREAD SDA,SCL,loc,[VALUE],Fail
	PAUSE 25
	DEBUG  HEX Value,13,10
	PAUSE 250
	DEBUG "Done....",13,10
WHILE 1 : WEND
Goto Main

Fail:
	toggle portc.2
goto main

[Demon]

...
%00110111 = $37 ' Read function
%00110110 = $36 ' Write function
..

I would have thought:
%00000001 = $37 ' Read function
%00000000 = $36 ' Write function

I don't see in this datasheet where you get the rest.

Robert