Mcp23017 interrupt

[salvodjkr]

Hi everyone . technical question. is it possible to use only one interrupt for two mcp23017?

[tttapa]

Yes. The interrupt pins are configured in open-drain mode:

Control-Surface/src/AH/Hardware/ExtendedInputOutput/MCP23017.ipp

Lines 83 to 93 in 344324d

	// Set the IOCON register (configuration register)
	writeI2C(IOCON, //
	0b01100100);
	// │││││││└─ Unimplemented
	// ││││││└── INTPOL = Active-low
	// │││││└─── ODR = Open-drain output (overrides the INTPOL bit)
	// ││││└──── HAEN = Disables the MCP23S17 address pins
	// │││└───── DISSLW = Slew rate enabled
	// ││└────── SEQOP = Sequential operation disabled, address pointer does not increment
	// │└─────── MIRROR = The INT pins are internally connected
	// └──────── BANK = The registers are in the same bank (addresses are sequential)

[salvodjkr]

Hi Pieter, thanks for the immediate response. another question . given the complexity I decided to use a single interrupt, I have no skills to modify my code. what maximum distance can I use for the interrupt cable??.

[tttapa]

This will depend on the strength of the pull-up resistor you're using, and on the noise in the environment. You're much more likely to be limited by the length of the I²C wires: it's not meant to be used over distances longer than a couple of centimeters, maybe 30cm at most.