Hi, I'm working on a project where I need to expand a Photon's number of digital GPIO's to around 60...
It seems an ideal solution to me to use four MCP23017 I/O expander ICs.
I tried the library examples with one IC today and everything works perfectly. The fact that you can configure every one of the 16 I/O pins as INPUT and OUTPUT is exactly what I need!
I know the 3 hardware address pins 15~17 are used to determine the I2C bus address for the chip, but I cannot figure out how to address pins on each of the four ICs...
All library examples contain this line:
mcp.begin(); // use default address 0
I guess to address 3 more chips, you should hardwire them to address 1, 2, 3 and use an extra identifier in the code, right?
Can anybody help?