Raspi and Pic i2c problem

[zydis]

Hi, I am using raspi as master and pic18f67k22 as slave.
Here is my code to define i2c for pic.

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#use i2c(SLAVE, sda=PIN_d5, scl=PIN_d6, address = 0x40)

when I use this command at raspi terminal, address of pic is shown half of 0x40.

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pi@raspberrypi ~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: 20 -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Then whenever I use "sudo i2cdetect -y 1" raspi return nothing.

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pi@raspberrypi ~ $ sudo i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Do you have any idea about this problem?

[brekee12]

Probably it is only a "ghost" signal. Check your I2C pins I can remember other pins.

[6by9]

I2C has an 8 bit slave address field. The top 7 bits are the device id, and the bottom bit is the read/write bit.
Some systems use the entire 8 bit value when referring to an address. Others (including Linux) only use the actual address bits.
It sounds like your PIC is taking 0x40 as the full 8 bit value, so Linux sees half of it when it has knocked off the bottom direction bit.

[zydis]

And also i2c address map on raspi is not permanent. After first search address of 0x20 is disapearing and "sudo i2cdetect -y 1" shows nothing.

[6by9]

And also i2c address map on raspi is not permanent. After first search address of 0x20 is disapearing and "sudo i2cdetect -y 1" shows nothing.

I'm no expert on PICs, but typically you need to give it some data to send back on a read (which is what i2cdetect is using). Does it send anything if the transmit FIFO is empty? Quite possibly not.

[andornot]

It looks like you are using the CCS PICC compiler. In your #USE statement the address must be 2 x the address you wish it to be. If you want the address to be 0x40, you must enter 0x80 in the address field of the #USE like this:

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#use i2c(SLAVE, sda=PIN_d5, scl=PIN_d6, address = 0x80)