mesecons/mesecons_microcontroller/doc/microcontroller/description.md

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<!-- Generate `description.html` from this by using `$ md2html -o description.html description.md`. -->
The Microcontroller is a semi-advanced programmable component with a persistent
256 bit EEPROM memory.
Warning: This device is largely considered deprecated and might contain bugs. It
is recommended to use a Luacontroller instead.
Detailed documentation can be found below:
* The Microcontroller's code is executed whenever any of the following events
happens:
* The Microcontroller is programmed. In this case the EEPROM and ports are all
reset to `0` before.
* An incoming signal changes its state.
* An `after` event happens (see command `after` below).
* There are 4 I/O ports (ABCD) and 256 EEPROM bits (1 to 256).
* The code consists of a sequence of commands.
* Everything after `:` is a comment.
* Strings are enclosed in `"`s.
* Spaces and tabs outside of strings are ignored.
* Basic command syntax:
```
command_name`(`param1`,` param2`,` ...`)`
```
* Commands:
* `if(condition) commands [> else_commands];`:
Evaluates the given condition and takes the corresponding branch.
The else branch is optional (as indicated by the `[` and `]`). The `>` is part
of the syntax and indicates the start of the else branch. The `;` marks the
end of the if command.
* `on(port1, port2, ...)`:
Sets the given ports to `1`.
* `off(port1, port2, ...)`:
Sets the given ports to `0`.
* `print("string" or codition, ...)`:
Evaluates the conditions and prints the concatenation of all params to stdout
(only useful in singleplayer).
* `after(time, "more commands")`:
Executes the commands in the string after the given time in seconds.
There can only be one waiting `after` event at once.
Warning: This is not reliable, ie. `minetest.after` is used.
* `sbi(port_or_eeprom, condition)`:
Evaluates the condition and sets the port or EEPROM bit to the resulting value.
Note: EEPROM indices don't use `#` here, ie. it's `sbi(1, #2)`, not `sbi(#1, #2)`.
* Conditions (sorted by descending precedence; they are all evaluated from left
to right):
* `0`, `1`: constant
* `A`, ..., `D`: value of a port. Takes writes that already happened during the
current execution into account.
* `#1`, ..., `#256`: value of an EEPROM bit. Takes writes that already happened
during the current execution into account.
* `!condition`: negation (can only be applied once, ie. not `!!1`)
* `condition1 = condition2`: XNOR (equality)
* `condition1 op condition2` where `op` is one of:
* `&`: AND
* `|`: OR
* `~`: XOR (inequality)
* Note: Explicit precedence using parentheses is not supported.