Problem reading 24FC1025 EEPROM with 18f14k22

[Dave]

I bet it's that there are no pullup resistors on the SCL and SDA lines when using I2C command. The SHIFTOUT and SHIFTIN command use the pins in a sink and source mode but the I2C mode reverses the the data pin direction at the end of the byte sequence looking for the ACK bit from the slave device. There must be a pullup on the data line to provide sourcing current back to the PIC. If the PIC does not see the proper ACK signal then the command sequence is aborted.

[JimAvanti]

I am running at 16MHz with the Internal OSC. I do have a 10k pullup on the SDA line. I tried a 2k as well and it did the same thing. I don't have any pullups on the SCL line now, but I did try that before with no luck. I will try it again. I may drop a 16f690 in for testing purposes (Pin compatable with the 18f14k22 and I know they work with this EEPROM).

I bet it's that there are no pullup resistors on the SCL and SDA lines when using I2C command. The SHIFTOUT and SHIFTIN command use the pins in a sink and source mode but the I2C mode reverses the the data pin direction at the end of the byte sequence looking for the ACK bit from the slave device. There must be a pullup on the data line to provide sourcing current back to the PIC. If the PIC does not see the proper ACK signal then the command sequence is aborted.

[JimAvanti]

Dave & DEMON,
Problem solved! I added the 10k pull-up resistor to the SCL line as you suggested and everything started working. I did have a 10k on both the SCL and SDA lines originally, but at that time I must have had something else wrong. I checked the datasheet which only stated pullup of 2k-10k on the SDA line so I removed the SCL pull-up and never put it back. I was able to fully load the EEPROM and now I can read an entire string from EEPROM at a time (Much better than the ShiftIn/Out way). I guess since the Shiftin/out was working I assumed the electronics was correct. I have used these EEPROMS in the past and never had an issue. I guess I should have looked at my old schematics before pointing the finger at Pic Basic!

Thank you all for the help!

Jim

I am running at 16MHz with the Internal OSC. I do have a 10k pullup on the SDA line. I tried a 2k as well and it did the same thing. I don't have any pullups on the SCL line now, but I did try that before with no luck. I will try it again. I may drop a 16f690 in for testing purposes (Pin compatable with the 18f14k22 and I know they work with this EEPROM).