I2C address clash

Projects Networking, Protocols, and Devices
1

I am using 3 I2C chips in the latest project, the first is the SAA1064 with its address set to 0x70, and the others are a pair of PCF8574APs driving LCD displays.

The one display works fine with its 0x3F address, but the other with all its address pins grounded (0x38) was throwing out rubbish on the screen.

I changed the pins and address to 0x39 and its fine.

Just my luck on the first time I have mixed I2C chips on a board !

2

The problem is that the SAA1064 doesn't have the address 0x70 (ADR pin to GND) but 0x38 (Arduino uses 7bit addresses, 8bit addresses have to be shifted to the right one bit), so a clash is obvious.

3

Thanks Pylon,

I havn't had a chance to look at it in detail yet, I will have a look tonight if I get a chance