I2C, PIC16F877 and the SDA, SCL

[Kenan Vilic]

Hello,

I have a question about I2C on PIC16F877.

My program is as simple as follows:

#use I2C(master, sda=PIN_C4, scl=PIN_C3, fast)

i2c_start();
i2c_write(address); //7 bit address + 0
i2c_write(0xEE);
i2c_stop();

The thing I am wondering about is why the clock is not normal, even when a device is not attached. I try to measure with an oscilloscope and the clock is shovn as a fast capacitor charging
not as pulse train.

I have remembered to make pull-up resistors and have two devices connected to the bus a DS1624 (temperature sensor) and DS1339(RTC), but as I said even without the devices clock and data are behaving odd.

Can somebody tell me what is wrong?

Thanks In Advance
Kenan Vilic
___________________________
This message was ported from CCS's old forum
Original Post ID: 13567

[Kenny]

:=Hello,
:=
:=I have a question about I2C on PIC16F877.
:=
:=My program is as simple as follows:
:=
:=#use I2C(master, sda=PIN_C4, scl=PIN_C3, fast)
:=
:=i2c_start();
:=i2c_write(address); //7 bit address + 0
:=i2c_write(0xEE);
:=i2c_stop();
:=
:=The thing I am wondering about is why the clock is not normal, even when a device is not attached. I try to measure with an oscilloscope and the clock is shovn as a fast capacitor charging
:=not as pulse train.
:=
:=I have remembered to make pull-up resistors and have two devices connected to the bus a DS1624 (temperature sensor) and DS1339(RTC), but as I said even without the devices clock and data are behaving odd.
:=
:=Can somebody tell me what is wrong?
:=
:=Thanks In Advance
:=Kenan Vilic

Try adding:
setup_spi(FALSE);
also leave out "fast" in
#use I2C(master, sda=PIN_C4, scl=PIN_C3, fast)
for testing until you have found the problem.
Pullups should be around 2k2 (see i2c specs).
Let's know how you go.

Regards
Kenny
___________________________
This message was ported from CCS's old forum
Original Post ID: 13568

[Kenan Vilic]

Hi,

:=Try adding:
:=setup_spi(FALSE);
Did not help

:=also leave out "fast" in
:=#use I2C(master, sda=PIN_C4, scl=PIN_C3, fast)
:=for testing until you have found the problem.
Tried that, no difference

:=Pullups should be around 2k2 (see i2c specs).
Hurray!!! that was the problem... I had to use 56k pull-ups for a hall switch so I used the same for the I2C lines...Changing them was the solution.

Thank you very much Kenny
Kenan
___________________________
This message was ported from CCS's old forum
Original Post ID: 13584