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I'm trying to use the MCP23017 I2C port extender which has 3 addressing pins to be externally biased to set the I2C device address.

How should I connect the 3 addressing pins to select the I2C address that I want? I was not able to identify a table mapping the biasing to the I2C address in its datasheet.

Also, should I be biasing by connecting some address pins to GND, some to 5V of my Raspberry? Diagram below show show I am currently wiring up three MCP23017 to a single Raspberry 3. Does the wiring look ok?

[Link to clearer image]

enter image description here

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  • \$\begingroup\$ table 1-1 and figure 3-6 in the datasheet \$\endgroup\$ – jsotola Jan 18 '18 at 17:21
  • \$\begingroup\$ you can iterate I2C devices, so just try a combo and scan. \$\endgroup\$ – dandavis Jan 18 '18 at 20:41
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Figure 3.4 (Page 15 of the datasheet shows the device addressing), and yes A0,1,2 are digital inputs, 0 or 5V depending should be fine.

Read the device errata I recall being being some shenanigans, but that may have been only the SPI variant.

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  • \$\begingroup\$ Thank you! Am I right to say that in the schematic in the question, the bottom most MCP23017 has a slave address of 0x20, and the top most MCP23017 has a slave address of 0x22? \$\endgroup\$ – Nyxynyx Jan 18 '18 at 18:52
  • \$\begingroup\$ In 7 bit format, yes. \$\endgroup\$ – Dan Mills Jan 18 '18 at 20:01

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