Hashes at run time

So far your code always knew which device hangs where – you connected it yourself. A chip that other players take from the library does not know that. But it can ask: every logic-capable device reports what it is and what it is called.

Three identifiers#

PrefabHash is the same number that HASH("StructureGasSensor") returns. NameHash the same as HASH("Raum"). So you simply compare with a define:

l kind d0 PrefabHash
seq tmp kind SENSOR          # 1 = a gas sensor is on d0

Recognising devices on pins#

With the indirect pin dr0 (day 102) a loop walks through all six pins. bdns skips empty pins before l raises an error:

move pin 0
loop:
bdns dr0 next             # empty pin: skip
l kind dr0 PrefabHash
next:
add pin pin 1
blt pin PINS loop

That way the chip counts how many sensors and batteries it has, and finds the device with a certain name – no matter which pin it sits on.

What it is good for#

• Self-check: a chip checks at start whether there really is a gas sensor on d0, and reports an error otherwise instead of controlling nonsense.
• Universal display: depending on the device type the chip reads Temperature or Ratio.
• Names instead of pins: the chip looks for “Haupt”, whether somebody put the battery on d1 or d3.