Paul  wrote, quoting Tracy Crooke:

Data sent in following order:   (10 bit values are sent as 2 bytes, LSB
first, right justified)

Start Flag  (8 bits)  F0 hex  Indicates start of data group.

1.    O2 sensor output.  fuel/air mixture (10 bits)  255 = stoic. mixture.
      higher = richer
2.    MAP  manifold pressure (10 bits)  841 = 30" Hg. , 200 = 10" Hg.
3.    Air temp (engine inlet ait temp) (10 bits)  511 = 25 degrees C. (curve
      not defined yet)
4.    PGM  current setting of programming knob. (10 bit) 0 - 1023)
5.    Mixture current setting of mixture knob  0 - 1023
6.    Fuel Flow (10 bit) 0 - 511    511 = approx 20 GPH on 13B, 30 GPH on
      20B
7.    Table data in use.  (10 bit) Current mixture correction table entry.
8.    engine speed (10 bit) (1 mhz clocks during 30 degrees of crankshaft
      rotation)
9.    Table address  (8 bit) 0 - 63  Address of current table entry in use.
10.    Staging flag (8 bit) 0 or 1,  If 1 then fuel flow must be divided by
       2 (one injector per rotor in use)
11.    EOX  end of message byte (8 bit) F7 hex

Russell Kent wrote:

Paul or Tracy,
Item 8 (engine speed) works out to a *minimum* measured engine speed of about 4,887
RPM.  That seems like a very high threshold.  The upper end of the measurement window
is 5,000,000 RPM.  Perhaps it doesn't matter, but one can lower useful range by
either adding a few significant bits (each one halves the minimum measured RPM) or
putting a "divide-by" circuit in the 1 MHz pulse chain.

Also, perhaps item 6 (fuel flow) should be re-labelled "fuel injector duty cycle".
This would help clarify (to me, at least) what's being reported so that item 10
(staging flag) makes a bit more sense.  Then fuel flow becomes: 20 * duty cycle /
(511 * (staging +1)) GPH.

Russell Kent

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