18LF2620 I2C Problems

UFAnders · Joined: 13 Apr 2005 Posts: 36 Location: Michigan

Gentlemen of the forum-->

I have been using an 18F2520 for my current project without error, but I ran out of program ROM. So I got a sample lot of 3 18LF2620s, included the proper header, and loaded the same program into the new chips.

My problem is that my I2C LED modules that are essential to this project aren't being found anymore! (I send a simple START>REG>DATA command to get the ACK)

Everything was working perfectly with the '2520s but now the I2C functions aren't working properly. Any ideas? Do I need to send an i2c_stop() before doing a start? I am using PCH 3.217.

Thanks!

asmallri · Joined: 12 Aug 2004 Posts: 1635 Location: Perth, Australia

kender · Joined: 09 Aug 2004 Posts: 768 Location: Silicon Valley

Also, what's your PIC's power supply voltage?
What's the value for the pull-up resistors?
Can you talk to other devices on the I2C bus (ther than LED drivers)?

UFAnders · Joined: 13 Apr 2005 Posts: 36 Location: Michigan

Thanks for the replies, guys!

1. I am using the internal oscillator at 8MHz with no PLL

2. I am running the system at 3.3 volts, running a 5.2 volt cell phone wall wart (800mA) through a TC1263 vreg from Microchip

3. I am using 4.7k pullups in the I2C bus

4. I have a 24AA512 serial EEPROM also on the I2C bus but I haven't gotten far enough in my program to use it

I appreciate your questions, thanks for helping me out!

UFAnders · Joined: 13 Apr 2005 Posts: 36 Location: Michigan

Guys, I have inexcusably wasted your time.

I have wires on my protoboard that run from the I2C pins first to my EEPROM, then cascade over to my light modules. It seems that when I swapped the 2520s out for the 2620s I had connected the SCL wire to some other pin on the EEPROM, so no devices were getting any clock signals.

I fixed my retarded blunder and everything works. I'll take more time to double check my wiring before posting to the forum in the future.

Please accept my sincerest thanks and apologies.