I am using the Adafruit datalogger shield (Rev B) and a pair of cheap 20x4 LCD I2C displays. My UNO clone is the iteaduino-BT (One-stop Online Shop For Smart Home, HMI Display, Airspy, Diy Kits l ITEAD STUDIO), which is a board I really like.
I am getting interference between the LCD displays and the SD card function. Sometimes I can write to the SD card, and sometimes I can't. I have tried several SD cards. After a lot of experimenting, I think I have identified the problem. The LCDs are interfering somehow with the SD card functions. The LCDs are created with the following statements;
// set the lcd1 address to 0x26
// Set the pins on the I2C chip used for lcd1 connections:
// addr, en,rw,rs,d4,d5,d6,d7,bl,blpol
LiquidCrystal_I2C lcd1(0x26, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
// set the lcd2 address to 0x27
LiquidCrystal_I2C lcd2(0x27, 2, 1, 0, 4, 5, 6, 7, 3, POSITIVE);
If I comment out the LCD lines, the SD problem goes away. My thinking is that the four data lines used by the LCDs (4,5,6,7) may be overlapping with the datalogger card, but after looking at the datalogger schematic, I can't see the problem. I found a couple of websites saying that I can map the LCDs to use different data lines, but I'm not sure if that is the problem. I do have SDA and SCL jumpers soldered on the bottom of the datalogger card.
I would greatly appreciate any help.