I2C Read and Write

[DerekMacom]

Hi I was wondering if anyone could give me a clue as to what's going wrong here, it's driving me nuts? Signals look ok as far as I can see, 4k7 pull ups fitted on both lines

I've got a P18f252 interfaceing with a 24LC84 eeprom, it's in HS PLL mode, the eeprom is the only device on the bus...

Any help would be appreciated.

My code is sitting in a loop with the following code...

'defines
'DEFINE OSC 40 ' Operating frequency
'DEFINE I2C_SLOW 1
'I2C_CON CON %10100000 ' Memory I2c control byte
'i2c_sda var PORTA.0 ' I2C serial data line
'i2c_scl var PORTA.1 ' I2C serial clock line

mem_off = 0;
MyWordWr = MyWordWr+1
i2cwrite i2c_sda, i2c_scl, I2C_CON, mem_off, [MyWordWr]
i2cRead i2c_sda, i2c_scl, I2C_CON, mem_off, [MyWordRd]

ram[F05_HI] = MyWordRd/256 'This register can be read over modbus
ram[F05_LO] = MyWordRd

ram[F10_HI] = MyWordWr/256 'This register can be read over modbus
ram[F10_LO] = MyWordWr

[JD123]

'I2C_CON CON %10100000 ' Memory I2c control byte

change this to a var, not con

from the pbp manual:

" Constants should not be used for the address as the size can vary dependent on the size of the constant. "

[DerekMacom]

Hi thanks for replying... though the 'I2C_CON CON %10100000 ' is my control byte, not the address which is 'mem_off' and declared as a word.

I'll give it a shot though.

Thanks again.

Derek

[DerekMacom]

Defining the control byte as a var didn't help... so I need to keep looking (

Also I've noticed that if I put a 10ms Pause between my write and read my serial coms stops responding, does the PAUSE command disable the interupts or something?

[mister_e]

Make sure you have disabled all multiplexed Analog modules on the pin you're using. (ADCs and/or comparators)

http://www.picbasic.co.uk/forum/showthread.php?t=561

Could be interesting to see your config fuses setting... and the whole code.

[falingtrea]

Well, I did a search for a 24LC84 and could not find a data sheet anywhere. What size is this part? If it is bigger than 32 kbits, then it probably needs a word size value for mem_off. For your ram_lo data I think you should mask off the upper byte by and'ing MyWordWrite and MyWordRead with 0xFF. Or use the .lowbyte and .highbyte modifiers. In fact, I don't see size definitions for any of your variables. Is mem_off a byte or word variable? Is ram a byte or word array? What are F05 and F10 defined as?

[falingtrea]

Also I've noticed that if I put a 10ms Pause between my write and read my serial coms stops responding, does the PAUSE command disable the interupts or something?

Serial rate of 9600 baud is about 1 msec per character so a 10 msec pause could definately cause problems. The manual says this about HSERIN:

"As the hardware serial port only has a 2 byte input buffer, it can easily overflow if characters are not read from it often enough."

You might have to break up the pause into chunks and do a serial read in between. Maybe do 3-4 HSERIN or SERIN calls with a 2-3 msec timeout.

[JD123]

Tim, it doesn't look like he's using the HSERIN. Ports RA.0 and RA.1 aren't the serial ports on this PIC.