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EA: Set the active EXP board address, EXP Bus Protocol Reference

Understanding EXP board addressing

This command is used with FAST Expansion and FAST breakout boards via a FAST Serial Protocol (FSP) connection to the EXP Bus. Please read the EXP Overview to understand the operation of these commands and addresses.

The EA: command is used to set the "active" board. When an EA: command is sent, all subsequent commands without embedded addresses will be processed by the board that's active.

This command can be used with 2-character addresses for expansion boards, and with 3-character addresses for a specific breakout board on that expansion board. (Note that most commands are designed to be addressed to either an expansion board or a breakout board.)

In practical use, this command will almost always be used with a 3-character address for a specific breakout board. The 2-character expansion board addresses tend to only be used during startup (via ID: commands to confirm the boards are responding), and via other occasional things (like the BR: command which is typically sent to reset the machine hardware once a game is over.)

The EA: command does not provide feedback. If an invalid board address is used, you will not know it. If you want to confirm that the EA: "worked", you could send an ID: afterwards. (This is not recommended for your general use code, but it's nice when you're playing around via a terminal emulator). For example:

ea:b4
id:
ID:EXP FP-EXP-0071  0.8

Or, if you want to get the ID of a specific breakout board:

ea:b40
id:
ID:BRK FP-EXP-0071  0.0

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