# Board Addressing

Each Opera Cake has a numeric address set by optional jumpers installed on header P1. The default address (without jumpers) is 0. The `--list` or `-l` option can be used to list the address(es) of one or more Opera Cakes installed on a HackRF One:

    hackrf_operacake -l

The address may be set to any number from 0 to 7 by installing jumpers across the A0, A1, and/or A2 pins of header P1.

Address | A2 Jumper | A1 Jumper | A0 Jumper
--- | --- | --- | ---
0 | No | No | No
1 | No | No | Yes
2 | No | Yes | No
3 | No | Yes | Yes
4 | Yes | No | No
5 | Yes | No | Yes
6 | Yes | Yes | No
7 | Yes | Yes | Yes

When configuring an Opera Cake, the address may be specified with the `--address` or `-o` option:

    hackrf_operacake -o 1 -a A1 -b B2

If the address is unspecified, 0 is assumed. It is only necessary to specify the address if the address has been changed with the addition of jumpers, typically required only if multiple Opera Cakes are stacked onto a single HackRF One.