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[[User:Edrabbit|Ed]] and [[User:sofauxboho|Reed]] bought the light bar at the Prototype This garage sale in February '09. While it wasn't explicitly stated, it was fairly obvious that the device had been abandoned there by the Navy when they pulled out of Treasure Island in the mid 90s. This was corroborated by the US Navy Property label affixed to it.
From what I (Nils) can remember, the light bar came from some decommissioned fire marshal car. I don't remember who it was that brought it in or was working on it.
 
Our goal is to get it working for use on Ed's car at 4th of Juplaya and Burning Man. It is available for non-destructive sharing at other times.
 
We looked it over with Jonathan Moore and Mitch, and were then distracted by other projects.
 
[[User:shkoo|Nils]] has since been working on it and has discovered the following:


This thing uses all 12-volt logic, which makes sense since it would've been powered off a 12 volt battery.
This thing uses all 12-volt logic, which makes sense since it would've been powered off a 12 volt battery.
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The guy that was working on it successfully activated some of the lights and the motor to turn the lights by poking at connections internal to the light bar.
The guy that was working on it successfully activated some of the lights and the motor to turn the lights by poking at connections internal to the light bar.
== Operation ==
There is a single serial data line that runs into the light bar.  It is demultiplexed via a motorola 145029 and a pair of 4099 addressable latches.
The format of serial packets is a sequence of 9 bits:
  0: always 0 (used for addressing)
  1: always 0 (used for addressing)
  2: always 0 (used for addressing)
  3: always 0 (used for addressing)
  4: when 1, address IC609 (PTT, RADIO, MANUAL, AIR HORN, TAKEDOWN, STROBE, LEFT ALLEY, TAP II)
    when 0, address IC608 (switched power(?), SECONDARY, PRIMARY, WAIL, YELP, HI-LO, FLOOD, RIGHT ALLEY)
  5, 6, 7: address output within IC609/IC608
  8: when 1, enable function
    when 0, disable function
The serial bytes are sent in a format documented in the 145026 datasheet.  (The trinary/high impedence capabilities of the 145026 are unused.)
The 145026 multiplexer has the following hooked up to the timing pins:
  RTC(13) 10 kohm
  CTC(12) 470 picofarad
  RS(11) 22 kohm
According to that, the multiplexer should run at a clock speed of 1/(2.3 * 10 kohm * 470 picofarad) = about 92.506938 Khz.
The 14029 demultiplexer has the following hooked up to the timing pins:
  RI(6) = 12 kohm -> CI(7) -> 1500 picofarad -> ground
  R2/C2(10) = 110 kohm, 3300 picofarad
But the datasheet does not give us good timing information for that, but it looks close to the table given in the 145026 datasheet so I believe we're good.
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