I2C CONFUSION, Help needed please

[Demon]

I thought I saw 9 bits used from control in the datasheet you linked.

Maybe you're supposed to use a word and ignore the other 7 bits? Or that could be handled by PBP for I2C?

Do you get only a byte back, word, multiple bytes?

Your circuit does make address 0 right?

(just throwing ideas at you)

Robert

[FromTheCockpit]

Steps Taken:

1) Configuration changed: _INTRC_OSC_NOCLKOUT
2) Made 16f688 run at 8MHz : OSCCON=%01110001
3) Commented DEFINE I2CSLOW 1
4) Value changed to BYte (then to word again)

I get a byte back from the device (from what I have understood). Yes there is an address 0 in the device. I should get back chip ID i.e-'2E' as per the datasheet.

Still no Luck.

[LinkMTech]

I couldn't find detailed info on the Write/Read bit of the device address. But I will guess it is bit 7.
You need to Write to the device first using the address with the "Write" bit set.
$1B or %00011011 becomes $9B or $10011011

Without confirming the proper syntax of the commands, here's something off the top of my noodle:

This will cover steps 1~4 of Section 4.3.2 of the datasheet

I2CWRITE SDA,SCL,[Addr,Loc,]  ' Addr plus Write bit = $9B

This will cover steps 5~7 of Section 4.3.2 of the datasheet

I2CREAD SDA,SCL,[Addr,Loc]   ' Addr plus Read bit = $1B

Putting it together should get you moving in the right direction.

I2CWRITE SDA,SCL,[Addr,Loc,]  ' Addr plus Write bit = $9B
I2CREAD SDA,SCL,[Addr,Loc]   ' Addr plus Read bit = $1B

Here's a note to myself that might come in handy too:

[FromTheCockpit]

Tried this:

Pause 500
	DEBUG "Start......",13,10
Value=0
Addr=$9B
Loc=0

Main:
High Led : Pause 500: Low Led : PAUSE 500
	I2CWRITE SDA,SCL,ADDR,LOC
Addr=$1B : PAUSE 50
	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

Didn't worked. (Value/Addr/Loc = Byte size)

'=======
Can I not the Micro at 4MHz? The Datasheet says MAX speed is 400KHz, so I assume lower speeds are supported. Am I right?

[LinkMTech]

Remove the PAUSE 50 after I2CWRITE because the device starts sending immediately if its happy.

Then try bit 6 then 5 instead for the Write bit if the Write bit position was a wrong guess.
Bit 6 = $5B
Bit 5 = $3B

[LinkMTech]

Yeah, 400kHz is the max speed so at 4MHz it will run closer to 100kHz

[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?