I2C question

xpercad · Joined: 27 Jun 2004 Posts: 12 Location: MÉXICO

I am using PIC18F252 PCWH 3.205 and I2C FAST software generated bus for FRAM memories. I have 2 2.2k pull-up resistors and using pin RA2 for SDA signal and pin RA3 for SCL signal.

From time to time the FRAM memory gets corrupted and I wonder if there is some electrical limitation in using RA2 and RA3 for the I2C bus.

Your help will be most appreciated.

Best Wishes,

Aaron

xpercad · Joined: 27 Jun 2004 Posts: 12 Location: MÉXICO

What I meant to ask is: the dedicated pins of the PIC18F452 for I2C (RC3 & RC4) have both Schmitt Trigger buffers, and the pins I am using (RA2 & RA3) do not.

Has anybody had any experience using pins (RA2 & RA3) for I2C and had memory corruption problems ???

Regards,

Aaron

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

Most likely, if nobody answers then nobody has experienced this phenomenon. Maybe you could try using the hardware I/O to see if it stabilizes. Then, use a different pair of pins to see if it gets flakey again. If you keep having problems with the non-hardware pins try setting the Slow parameter in your #use declaration. Who knows, it could help.

Good luck

Ronald

valemike · Guest

I have not had any problems myself.

However, I do know of cases where a noisy environment can corrupt your i2c data. That is why the hardware guy put a few small caps on the SDA/SCL lines. Try lowering your i2c speeds as well.

rnielsen · Joined: 23 Sep 2003 Posts: 852 Location: Utah

Caps on I2C bus lines is not a good idea. The I2C protocol states a maximum of 400pf on the bus lines.

xpercad · Joined: 27 Jun 2004 Posts: 12 Location: MÉXICO

Thanks guys. I will try the SLOW option and I'll report back....