turn off i2c with FORCE_HW

[asancheti]

Hello,

I have a program which runs a series of tests on hardware to which the PIC16F873 is connected. The bulk of the tests require me to communicate VIA i2c, which is no problem.

However, one of the tests require that I manually toggle output bits on and off, and read inputs. This would not be a problem except that the lines I must manually toggle are harware connected to the i2c lines. I am not using the i2c at the time when I must manipulate the bits, but when using the i2c port in forced hardware mode (FORCE_HW) I am unable to manipulate logic levels on those pins (PIN_C3 and C4).

If I remove the FORCE_HW option I can control the logic level, and everything is ok, except my program is a little to large to fit in the PIC's ROM when I have software I2C. So I need to use FORCE_HW.

So I guess I'm wondering if there is a way to set i2c to FORCE_HW and turn it off again half way through the application, so I can manipulate PIN_C3 and C4.

Thank you for your time.

- Ajay Sancheti

[PCM programmer]

You should read the data sheet. In the I/O Ports section,
look at the comments on "peripheral override".
The "Force_HW" mode uses the Hardware i2c module.
This overrides the normal port i/o ability on pins C3 and C4.

Here is a program which shows how to temporarily
disable the Hardware i2c. Then you can change those pins.

#include "16F877.h"
#fuses XT, NOWDT, NOPROTECT, BROWNOUT, PUT, NOLVP
#use delay(clock = 4000000)
#use i2c(Master, sda = PIN_C4, scl = PIN_C3, Force_HW)


#bit SSPEN_BIT = 0x14.5

#define enable_ssp() output_float(PIN_C3); \
output_float(PIN_C4); \
SSPEN_BIT = 1

#define disable_ssp() SSPEN_BIT = 0

main()
{

disable_ssp();

enable_ssp();

while(1);
}