It executed it's first program. Had a wiring error but it can be fixed
with
jumpers.
The silver lever is a Aries zero insertion force socket for getting the
chip
in and
out quickly for programming purposes. There is no on board in circuit
programming
for this version. You must have a stand alone programmer.
It is not fully populated yet but all the other circuits have been tested
on
the bench.
Paul Lamar
NICE !
Barron
I am thinking of going one step up on processors to the 80C51.
It is at least four times faster than the 8051. It has built in USB and
PWM mode for the timers.
BTW I am up in Monterey for the rotary races. Mazda owns the race track.
We flew in to San Francisco which was a big mistake, You have to take a
train to get a rental car. The people up here are logic and reason
challenged. They could have built a big parking garage for the rental
cars
cheaper than the train. Total travel time was six hours. I could have
driven it in 4 and the cost would be much much cheaper if you need to pay
for airline tickets even with gas at $4 in CA. We don't as Robin is a
retired UAL A&P. The Comfort Inn has lousy Internet service. I am at
Denny's.
My dad had a bad experience flying standby- he flew from Charlotte to
Chicago and was trying to get back. Took 2 days for him to get a seat.
Seems like Chicago might be a tad busy.
I have my board up and running too. I set it up with staged injectors and
manual leaning, all of which seem to be working correctly. I read MAP,
temp
and RPM. I used a second board as a signal generator, and it worked well
up
to 6000 rpm where the generated pulse width was short enough that it was
having trouble reaching the threshold voltage to fire the coils. I think
that I may have to use a second chip like the 555 as a trigger for the
coil
to make sure it works at high rpm. At low rpm the CAS will trigger the
board, but didn't reliably fire the coils. It did fine at high speed.
It will be a bit before I can test it on the engine, I still have to fab
intake, install the radiators, etc. I did finally finish the left wing
except for installing the tip! Progress, little by little.
I will keep testing the code and the board and see how it holds up.
Paul, how many kb is your code file? Mine came in just under 10k total
uploaded to the board including the libraries for the digital temp chip.
The executed code is around 5k, the temp sensor I used has a built in ADC,
so it outputs the temp digitally.
Kevin Alderman
Kevin, What AT chip number are you using? ZBASIC uses the AT1280 and the
AT1281.
A lot of the problems with the timers are the same. Are you using software
PWM?
I am moving much faster with ZBASIC than MikroBASIC and the 80x51xx.
Mainly because the help is in my time zone and not half way around the
world :)
Paul Lamar
My board has the Atmega 2560 chip.
http://arduino.cc/en/Main/ArduinoBoardADK. Says that at 5.5 volts, it
will
execute 16 million instructions per second, 1 MIPS per Mhz, and it runs at
16Mhz.
The preliminary run showed it worked as planned. The only issue I had at
all was the signal generator board. I tried to simulate the input from the
CAS at 8000 RPM. I used the analog output of the Arduino Uno as the signal,
but the analog output is in the form of a PWM. When I "fired" the signal
generator at 9 usecs or less, the resulting voltage from the uno wasn't
sufficient to fire the coil. I tried it through a transistor that would
trigger at .7 volts, and it worked but had a delay that might make it
problematic at high RPMs. Need more testing. I have a high speed lathe that
I can stick the CAS in and turn it at 4000 RPM, and as we know the CAS
turns at half engine speed. Should simulate 8000 rpm effectively. I have
been working on my wings, avionics, etc. and trying to program an
electronic health database engine along with about a dozen other projects,
so I haven't gotten back to it- yet.
I programmed the Mega to read temp, MAP and RPM (which doesn't calculate
right at the moment) and come up with a pulse width. This is modified by
the analog input of a POT, with 3 volts being 1.00 and adjusting up or down
from there. I have my injectors staged with primary and secondary depending
on the pulse width. The ADC PWM uses 255 as max, so when injector 1 gets a
PWM over 255, injector 2 gets the remainder. That would be 100 percent duty
cycle, so I might reduce that to 200. I'll see how it goes.
Kevin Alderman
What is that injector width in ms? I think you will have interrupt
conflicts at 7000
RPM using the built in software PWM. As I understand it the PWM soft ware
disables
all other interrupts while it generates pulse widths. Same for RPM if you
are using a
timer. I did those two functions in hardware to avoid the interrupt
conflict problem.
You may not notice it if you trigger the 2nd gen ignition directly from
the 2nd gen
CAS. You will need an amp for that. A CD4050 or CD4049 CMOS chip will do a
wonderful
job if you use 3 or more gates wired in parallel.
BTW it won't work with coil on plug for those using the LS1 or RX8 coils
so don't
even think about it :) Kevin is using the 2nd gen coils which in essence
are the same
old coils from 50 years ago but have an igniter.
The 1260 chip is basically the same as the 1281 (128K flash 64 pin) ZBASIC
uses but
the 1260 has more flash memory. 256K flash instead. I think you mentioned
you are
only using 10K. Both run at 16 MHZ. I have the ZBASIC 1280 100 pin with
125K flash
board but the I/O is a bit overkill. I scaled back to the ZBASIC 1281
board 64 pin. A
bit cheaper at $80 rather than $100. Not including the EFI specific hard
ware.
Paul Lamar
Kevin, you might want to use a high speed buffer. F series buffers are
fast. Off my head I remember having good result with 74F245 and the swith
on ns level. Those are 5 volt parts. I assume.the coil trigers on 5V.
Henry Nee
I am considering a new strategy of using polling instead of an external interrupt
when the CAS cames in. The trouble with the interrupt is the computer may be in the
midst of sending some COM data to the tablet when it comes in. When the interrupt
service routine is finished it goes back to the COM program where it left off. That
could result in garbled characters.
If I latch the CAS pulse and sit in a back ground loop watching for the CAS and then
do what needs to be done I needn't worry about garbled characters. The down side is I
have only 8 milliseconds at 7000 RPM to get everything done before I need to go back
and watch for the CAS again. Since the COM baud (bit) rate is roughly 115,000 per
second and a character is around 10 bits that is 11,500 characters per second. 8
milli seconds is .008 seconds. That means I can only send about 90 characters max to
the tablet per engine rev. The characters would be coming in to the tablet at the
rate of 8000 x 90 /60 or 12,000 characters per second. That assumes I do nothing else
except send data to the tablet. In the real world my guess it would be half that
rate. Do other things for 4 milliseconds and send characters for the last 4
milliseconds. Send only 45 at a time. Then go wait for the next CAS pulse.
At 3500 RPM the computer would be wasting 50% of the time available to it.
That might be OK. The ZBASIC AVR computer is very fast. I could also read the RPM the
moment the CAS came in and do different programs that send out characters depending
on the RPM. At 3500 RPM and below I would have 16 milliseconds or more to work with.
This strategy is the sledge hammer approach but it is safe and you don't have to
worry about two or more random and asynchronous interrupts coming in at the same time
and conflicting.
Paul Lamar
Hey Paul,
The nature of the task at hand will always demand a significant
percentage of processor time if you insist on calculating the RPM from
the CAS which you are also depending on to sync up the ignition timing.
If you separate the functions into two different sensors you can
calculate the RPM at your leisure. Read the RPM from the flywheel teeth
instead of the CAS. Send your data to the COM port.
Task priority:
Ignition timing - get this wrong and she won't run
Injection pulse width/timing - get this wrong and she will run poorly
COM port - not required for flight, nice to have for data
RPM - gotta have it but does not need to be updated every revolution.
Spend your processor time on the high priority items. Calculate RPM
when you have time to spare. If you miss a rotation or two it won't
matter much on an aircraft engine. With that big old flywheel/prop
hanging off one end the rotational acceleration of the engine will not
be significant. Calculate the RPM from the flywheel teeth with a pulse
counter. Set the counter to trip every 25 teeth or so. Then you can
calculate the RPM for about 1/4 of a rotation. Reasonable accuracy with
minimal investment. Good enough is the enemy of perfection, but it's
good enough, and that's all you need. Doing it this way will require no
more than 25% of your processor time at worse for RPM calculation.
I wouldn't worry too much about the COM port. The COM port interface
will hold your data until it gets a clear to send signal from the
receiver. It will take care of setting the parity and stop bits and
controlling the baud rate for you. No need to use processor time for
that. Just set that up when you initialize the interface. Send the
data to the COM port interface one byte at a time. Most have a small
buffer that will store several bytes so the processor doesn't have to
hang on the COM function waiting for the byte to be sent. No partial
bytes will bet sent because the interface knows when there is something
in the buffer ready to be sent.
Mark LaPierre
There is no hand shaking in the COM port. Tx and RX only.
Counting the flywheel teeth implies an external time based interrupts. Say every
tenth of a second High level language and com program don't do well with random
external interrupts. If I were doing asm I would probably go that route.
One of my goals is to bring more people into the programming process by using easy to
learn basic.
Sub Main()
WaitForCas:
Do While <boolean-expression> 'stay in this loop until the CAS pulse comes in.
Call GetPin(xx) ' xx is CAS pin number
Loop
'got CAS. The CAS pulse came in.
Call PutPin(qq, zxOutputLow) 'qq is the pin that resets the CAS latch
'You need a latch on the CAS because at hi RPM the pulse is very narrow.
' the program might miss it.
Call PutPin(zz, zxOutputLow) 'disable the external 12 bit RPM CD4040 counter.
'zz is now the pin number that disable the counter
Read the high byte 'hi byte 8 bit port
GetNibble(xx,highbyte) 'extract the lower 4 bits of the high byte
Read the low byte 'lo byte 8 bit port
RPM = MakeWord(lobyte,hibyte) 'combine the two into a unsigned 16 bit integer
Call PutPin(yy, zxOutputHigh) 'YY is the pin that resets the CD4040 counter.
'Thats it for the external RPM CD4040 counter. You now have the RPM variable.
It is even easier with an analog tach. 8 bit resolution.
Just read a analog to digital converter pin.
GetADC(pin, RPM)
I'll test both and see which one works the best.
BTW you can download the ZBASIC and all the doc's from the web site for free.
http://www.zbasic.net/
The active forum is well maintained by the guy that wrote the ZBASIC.
ZBASIC is near identical with MikroBASIC Pro for the AVR so you have a back up.
The 1281n computer is only $80.
Paul Lamar
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