Prelinary Propeller tachometer results

yarisboy

I used the Frequency synthesis ver 1.1 by Beau Schwabe and set the constant to 200 HZ. The oscilloscope result from my ECM simulator agreed on time base. I used Jon Williams jm_freqin.spin as a base for a tachometer output. For a four cylinder four stroke engine we were looking for 6000 RPM. The Object returned 5997 RPM. By contrast the digital automotive tachometer from Fry's electronics returned 5,840 RPM. I "calibrated" my old BS2 tachometer using the cheapy auto tach so the older tachometer is off more that the traditional 2% at full scale. Oh thank heaven for 5 MHz crystals. I'm finally getting the hang of modifying OBEX software for my purpose.
Now, onward to serial display drivers. I meant to say Preliminary in the title.

Bluhair

Could you please post your code. I have been working on a similar project.

Thank You

yarisboy

The other files in the Zip downloads from OBEX remain unchanged.
'' =================================================================================================
''
'' File....... modified from jm_freqin_demo.spin (by Stan Cloyd)
'' Purpose.... Process signal from OBD2 tach signal through opto-isolator to pin 0 of the Propeller multi-processor
'' Original Author..... Jon "JonnyMac" McPhalen (aka Jon Williams)
'' Copyright (c) 2009 Jon McPhalen
'' -- see below for terms of use
'' E-mail..... jon@jonmcphalen.com
'' Started.... 09 JUL 2009
'' Updated.... 10 JUL 2009
'' Modified .. 19 August 2010
'' =================================================================================================


con

_clkmode = xtal1 + pll16x
_xinfreq = 5_000_000


con

#0, CLS, HOME, #8, BKSP, TAB, LF, CLREOL, CLRDN, CR ' PST formmatting control


obj

fc : "jm_freqin"
term : "jm_txserial"


pub main | f

fc.init(0) ' freq cntr on p0

term.init(30, 115_200) ' start terminal
waitcnt(clkfreq/10 + cnt)
term.tx(CLS)

repeat
term.str(string(HOME, "revs: "))
f := fc.freq ' get frequency
if f > 0 ' valid?
term.dec(f*30/10) ' print whole part, 30 constant is for 4-cylinder, four-stroke ICE.
term.tx(".")
term.dec(f*30//10) ' print fractional part
term.str(string(" rpm", CLREOL))
else
term.str(string("???", CLREOL))
waitcnt(clkfreq + cnt)


{{
*****************************************
* Frequency Synthesizer demo v1.2 *
* Author: Beau Schwabe *
* Copyright (c) 2007 Parallax *
* See end of file for terms of use. *
*****************************************
Original Author: Chip Gracey
Modified by Beau Schwabe
Modified by Stan Cloyd 8/19/2010
*****************************************
}}
{
Revision History:
Version 1.0 - original file created

Version 1.1 - For Channel "B" there was a typo in the 'Synth' object
The line that reads...
DIRB[Pin]~~ 'make pin output
...should read...
DIRA[Pin]~~ 'make pin output
Version 1.2 To generate an ECM signal for 6000 RPM, Output must be amplified to 0-12 volts for scale
and should be opto-isolated to protect your other Prop.
}
CON

_CLKMODE = XTAL1 + PLL16X
_XINFREQ = 5_000_000


Pin = 0

Frequency = 200 '200 Hz from the OBD port of an automotive ECM with a four-cylinder, four stroke ICE represents 6000 RPM tachometer readout.

VAR

OBJ
Freq : "Synth"

PUB CTR_Demo

Freq.Synth("A",Pin, Frequency) 'Synth({Counter"A" or Counter"B"},Pin, Freq)

repeat 'loop forever to keep cog alive

DAT
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