adafruit learning system Joy Featherwing Manual page 6

Because multiple featherwings of all kinds can be stacked, the I2C address can be changed if necessary. The Joy
Featherwing's default I2C address is 0x49, but soldering jumpers A0 and/or A1 can change this:
A0
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Optional Interrupt Pin
Soldering one of the jumpers for the optional interrupt will connect that pin of your Feather to the interrupt line on the
Joy Featherwing. This will allow your Feather to know whether a button has been pressed or released without having
to read each button over and over in a loop.
© Adafruit Industries
A1
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https://learn.adafruit.com/joy-featherwing
Addr
0x49 (default)
0x4A
0x4B
0x4C
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