i2c_start not starting!

Will Reeve · Joined: 30 Oct 2003 Posts: 209 Location: Norfolk, England

Hi,
I am having a spot of bother with some i2c code.
I am getting stuck in i2c_start(); I never get to my next line which is a i2c_write with the address! I am using the hardware i2c MSSP master mode. The code it's stuck in is:

01C8: BSF FC5.0
01CA: BTFSC FC5.0
01CC: BRA 01CA

FC5.0 is "Initiate Start condition on SDA and SCL pins. Automatically cleared by hardware"

in my case the hardware isn't automatically clearing it! Even with nothing connected to the i2c liens only 3k pull-ups it still doesn't get cleared.

Am I missing something?

P.S. PIC is 18F2520

Ttelmah · Guest

Have you looked at the errata sheet for the chip.
There is a problem if an I2C_START is repeatedly sent. In this circumstance the bit will not clear automatically, and will hang the code...
Send an I2C_STOP, before sending any I2C_START command, and it should prevent the problem.

Best Wishes