MICROFORUM

hi, I plan to use expander MCP23009. In my project I need three of MCP23009. Now, I am confused with addressing. The expander has no standard A0, A1, A2. Instead of this, it has analog addressing via resistor divider. The problem is, how precise should be resistors. The stability of resistors can affect the address, right?

I have never seen an application or circuit where multiple MCP23009 was used. If you use one MCP23009, set address input to zero. My opinion, analog address setting for multiple MCP23009 can result in problems and instability.

Why to use MCP23009 ? Texas Instruments has many expanders 8- and 16 bits. Some with open collector. All have standard addressing.