forbiddenera

Hey guys,

So, now that I'm up to speed on HTS I can run flex fuel. I've also got the code for the rom, I'm going to see if I can implement flex fuel as a blend from primary to secondary tables as an addition although there's no space left in the current version of the ROM, so that might be interesting. But that's not what this thread is about. This thread is about rigging up an ethanol content sensor and an "analyzer" as they call it to convert the signal for dirty cheap.

The average GM flex fuel sensor, as many may know, and some may not, outputs a PWM signal that is from 50hz to 150hz for ethanol content and encodes the fuel temperature in the duty cycle. Higher end aftermarket ECUs can easily be programmed to read such a signal, but most of us are running OBD1 ECUs with a chip/Hondata/Demon or something else that wants a simple 0-5v output.

You'll need a few things to do this, but it's pretty simple. There's a lot of DIYs on the net about this but I'm posting my own because the code for most was a bit off, mainly that the ones that read fuel temperature as well use pulseIn() while the frequency is read with a timer. This wouldn't really cause an issue if you were only using the Arduino to do the conversion (and many of you will just use it this way I assume) but if you want to do anything else with the Arduino (drive a screen, convert other inputs/outputs) then you're going to run into problems.

I've re-written the code so that it reads the pulse wide and duty via timers and interrupt service routines, meaning it won't block your main loop() if you want to do other things.

Things you'll need:
- a GM flex fuel sensor* that outputs this type of signal, I am personally using Part #13577379, I got it off a '13 Impala at the junkyard for $10 CAD. It's like $65 CAD new at rockauto. Funny how a very similar one costs $460. If you get from the junk yard, obviously cut some length off with the plug. If not you'll need the plug and some wire,
- an Arduino; I'm personally using a Mega 2560 as I'm going to be doing other things with it but you could use a nano ($~7)
- 2* 4.7k resistors
- a voltage regulator/buck converter - technically both the Nano and the 2560 can support input voltages from 7-20v. Recommended is 7-12v. The higher voltage you feed it, the hotter the onboard (linear) regulator will get. A lot of tutorials online suggest using another linear regulator in front of it, which will just move this heat dissipation as you're still using a linear regulator, this I recommend a buck converter. This is one I use often. It won't dissipate as much heat as it's a switching regulator.

* There's many other sensors you can use, I would recommend the flow-through type. You can even purchase pretty ones with AN adapters if you want to bling out. GM part number 12568450 or 12570260 are two other examples. I think basically all the GM flex fuel sensors output the same style signal.

Wiring:

I stole the pic from here because I'm too lazy to open photoshoop.




This wiring is basically accurate. "TGV connector" will be the 0-5v output for your ECU, you can use a 3.3 or 4.7k resistor there.

The other 4.7k resistor is a pull-up resistor, it pulls the signal up to 5v from the sensor (and the sensor will pull it down when it wants to), without this resistor you won't get a signal.

+12v should be fused. If using a relay you can fuse before the relay (on the current side, coil side should also be appropriately protected)

The pins for the Arduino are correct if using a Nano, except they didn't bother with temperature, if you want temperature on the Nano it would be pin #10. if using a 2560 like me then your input is going to pin #49, fuel ethanol output still pin #10 and temp on #11. Edit: I fried my pin#11 I guess, so I'll be using Timer5 and pin #46 instead. The timers, their registers, what pins they go to, how to control them and all that ****, is a little confusing and requires a bit of research; I'm going to try and make this easy as possible for generic people; this post will be updated as I dial this in better.

The code needs to be modified slightly for either Arduino as different timers need to be used. I'll see if I can't make the code a bit configurable for either system.

You can also add an OLED display (I'm using this one) if you want to view the sensors output in realtime on a screen. Personally with my 2560 I'm using this shield which gives me lots of 4-pin headers of the different connections, so I can easily plug my screen (has the same 4 pin connector) into this header and it works. If you're using a screen with a nano, you'll have to solder on the connections for the screen, there are plenty of tutorials on the 'net on how to wire up one of these screens to an Arduino.

One other advantage to my setup is that I can use a compustar remote starter antenna cable between the shield and the screen, which gives me like 8' of wire to put the screen where I please.

I suppose I'll also have to add code to configure whether or not you've got the screen.

forbiddenera

I'm not sure this forum has a good way to post code; I'll post on GitHub in a bit.

Please wait, code coming soon I just want to double check my temperature output is accurate.

I may also include an option to use a DAC instead of an averaged PWM output, but appropriate filtering should do the job, though I doubt our ECUs will know the difference but I want to test that too.. (I'll update the circuit with that as well if I find filtering is needed, although the pwm frequency is pretty fast, like microsecond pulses)

For anyone who wants an early peak:
https://pastebin.com/L6f2kHnj

forbiddenera

:'( I just broke pin 11 on my Arduino by accident. Oh well. Other pins exist I guess Going to have to use Pin#46 and Timer#5 I guess. Lets not fry that one. GRR.

Was trying to filter the signal out a bit and 'oopsed'..will have to find another pin..****..pin 11 was one of the few 10-bit pins.

Won't make that mistake again; but filtering the signal with an RC circuit should be enough for our purposes. We can always use an external DAC or use an op-amp with an RC circuit to smooth it out.. but again I'm not even really sure we need the smoothing with our ECUs.

forbiddenera

So, I'm not sure what I did with my pin but I've tested with some filtering and I get a perfectly stable signal, so the pwm frequency I'm using is more than high enough for our purposes, so we won't need a DAC. In fact my last test was with only like 490hz or something slow. Actual output freq of the PWM will be like 2mhz.

I tried to replicate my 'bad luck' with another microcontroller and I can't 'break' it even trying to, so must have just been some bad luck on that pin.

The code is almost ready; I just want to verify that when it's commanding say 2.5v out that our ECUs will read 2.5v input, I don't forsee any issues but I feel like proper testing is a fair thing to do before completely releasing this into the wild.

I'm also happy to put together kits for people who don't want to do it themselves, these kits would be strictly for the ECA function and use a much smaller microcontroller for the job, such as the nano/zero, this would also keep the cost down. The kit would basically be the microcontroller pre-programmed with the correct software and pre-wired so that you'll just have to plug in your sensor and run the signal to your ECU.

Cost of the kit would be just a bit more than the cost of the microcontroller plus shipping, so probably like $25 or so. I would include an option to add a small OLED screen for a bit more as well as the option to output the signals to a PLX multi gauge.

forbiddenera

Everything seems good with tests.

I've got it outputting to the OLED now as well..!

forbiddenera

Txdragon

It's caught my attention

forbiddenera

Thanks! I'll have the code polished up a bit soon and I'll go back and edit the OP with better details, I think I'm going to order a nano just to test with or something cheap that I can recommend and provide code for. Not everyone is going to need a 2560 with 60+ pins of IO, if they're only using the controller for the flex fuel then the smallest/cheapest is going to be the best bet. I have a Pro Micro which could be a possibility but maybe the Nano might be better. Although most small ones need headers soldered on, so that might be an issue; I want to make this as easy as possible, I don't know how many people are going to be wanting to solder stuff up, but again I'm also willing to provide kits.

All off-car testing is complete. On-car testing will need a bit of time while I sort out some other things. I'll post the code on github shortly - IMHO my code is an improvement on the code you can already find on the 'net for this, it uses the highest frequency PWM the microcontroller is capable of (will filter nicely, most 'duinos only have ~490hz or ~1khz pwm, we're doing more like..2mhz) and uses timers and interrupts for both signals and output, no blocking stuff.

Chrisfrom1986

iTrader: (1)

Posting for when I catch up to this in a few years. Another dso member doing great work.

DaX

iTrader: (1)

Love the DIY aspect. This is really cool.

forbiddenera

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dso? Lol haven't posted there in years..b only for me at the moment. But thanks.

I am going to order a few Arduino Nanos or similar right away and finalize the code for that variant so you guys can all get crackin'

Txdragon

If i'd ever purchase one, I'd be more interested in the plug n play version. I am not a code person. Lol!

forbiddenera

Good to know.

The DIY version won't require any actual coding though, just have to download my code and upload it to your Arduino, which is why I want to get some Nanos so my code is ready to upload for them.

For anyone wanting to DIY it, these will be the steps:
- buy Arduino, upload my sketch
- find a few resistors and capacitors.
- get flex fuel sensor
- wire it all together
​​​​​​
​​​​But I'm happy to offer a ready to go one.

steps for the premade version would just be:
- order kit from me
- get flex fuel sensor
- wire sensor to +12v, gnd and output to Arduino
- wire Arduino output to ecu.
- install oled display if wanted.
​​​​
Since there's some actual interest, I will order some parts for kits right now.

For now people will have to provide their own sensors but if there's enough demand I can stock sensors as well.

forbiddenera

Just trying to pick out the best Microcontroller to order now:

Choices:
1. Arduino Nano (~$50)


Good
- is small, is 5v
- built in programming
- takes upto 20v input, so don't necessarily need a regulator for it
- has 1k eeprom
Bad
- costs $50 each
- have to order
2. Arduino Pro Mini (~$15)


Good
- available locally
- is small, is 5v
- has 1k eeprom
Bad
- Needs FTDI/TTL interface for programming
- can only take upto 16v input max
3. Seeduino Nano (~$10)

Good
- is small, is 5v
- has 1k eeprom
- has onboard grove connector (can plug a screen right into the board)
- onboard LDO says 20v input max
Maybe Bad
- uses USB C
Bad
- have to order

After writing this out, I think the Seeeduino wins; the onboard connector which is compatible with the OLED screens is nice, although I'm going to have to figure out a shield/board/something for connecting the sensor and ecu outputs.

One option is getting a Grove shield and using those type of cables for everything:



Basically, you'd have a 4-pin cable coming from one of those headers, red and black will go to +12v and ground, unless I include a regulator in which case the main board will get power over the USB cable. The other two cables on the 4-pin would be your temperature and ethanol out. A 2nd 4pin cable could provide 12v and ground to the sensor (but the board would need 12v in, not using USB) and take input from the sensor.

While the Grove shield is an option, it's probably a better option for more hacker types like me. I'm thinking that the best solution for you guys might be a custom board or breadboard for this.

I was originally thinking of using one of these as a buck regulator:

I use them everywhere I need USB or 5v in a car usually. Give it +12v and GND and plug your USB device in.

Considering the prevalence of easy PCB ordering services, I may mock up a board for this and have some shipped out. The board would have an onboard buck regulator to give a good 5v for the board, some sort of plug interface for the sensor and ecu outputs. The screen could still be plugged into the header on the controller if I use the Seeeduino Nano.

I think I'm going to order 2-3 of the Seeduino Nano's and a couple of screens to go with them. I think then I will test them with a ~14.8v input and see how hot the onboard LDO gets; if it's more than I'm comfortable with then we will be using some sort of buck converter.



This is a quick janky schematic of what the wiring would look like if I do use a separate buck converter AND if I don't provide a perf board/premade board with the filter on it.

Do you guys think you can handle that? 2 resistors and a cap? And soldering +12v/gnd wires onto the USB converter?

If that's too much for you guys then I can definitely look into making a 'shield' that the Arduino can plug into and will just provide some plugs, probably 3 separate plugs:
Main plug: 2 wires, +12v/gnd
2nd plug: 3 wires, flex fuel sensor
3rd plug: 2 wires, 0-5v ethanol and 0-5v temp

The only issue is if I do make custom boards, it will increase the cost a bit and I will have to find some good circuit board connectors to use; partly why I liked the grove shield idea, it already uses common 4-pin plugs..

Any/all feedback is appreciated, I just thought I'd share and help some people DIY/save some cash.

theYBLEGAL

In for updates

I vote pro mini, but I'd prefer to solder it all. Would you even use the USB header for power? I think not lol. I could see it going into a 3D printed enclosure with regulator and LCD, and maybe just a whip/pigtail out of the box.

forbiddenera

What do you guys prefer as far as a screen goes? I would assume that most people would want real time feedback on a screen. It is optional to have though.


Square 1.12" 128x128 OLED, 16-intensity grayscale


"Widescreen", 128x64 OLED, monochrome (this is the one I have / pictured above)


- 128x64 pixels (same resolution as the OLED above) but in 47.1x26.5mm / 1.8" x 1.04".. I haven't used one of these or even seen one, I can't imagine they will be very good in bright light like the OLED would. It is probably about 2x the size of the OLED though.


- 3 color (black, red, white) e-ink display. 212x104 pixels in 2.13". this would not update very fast at all and probably have to flash during updates like a lot of eink does. could still be an interesting option. would be easy to read in light I'd bet.

There's also a square version of the eink, 152x152 @ 1.4"


This is also an option, 16 chars 2 rows, text only, RGB backlight.



And then the overkill option; touch screen, 320x240; would have to write a ton of code to take advantage of the touch screen. can't say how readable it would be. Not a realistic option if just doing E85 and nothing else. Although I admit I will likely post other DIY-type stuff that can be done with Arduino's in the future. You can actually run your whole engine off one (speeduino), though I haven't tried one yet, I think I'll stick with my Honda ECU for now. But could be cool! They have OBD1 adapter boards even.

I would say the 2nd OLED is maybe a bit smaller than the OLED in the PLX gauge and is probably the best option but I thought I would seek input before ordering any.

These are just all displays that would easily plug into the Seeduino controller, can use a 4-pin CompuStar antenna cable (I can supply) to the screen for easy install.

forbiddenera

This is awesome input. I don't think most want to solder anything though, and if I can put a kit together for a decent price with/without a screen where they don't have to.

I don't have a 3D printer. If anyone wanted to help with an enclosure, that would be awesome. I was actually going to start researching what type of enclosures are already available for this formfactor.

We don't need much other than the board: 5v pull up for the FF sensor, RC filter(s) for the 5v output(s), plural depending on whether the user wants temperature output as well.

I like the seeduino board just because of the onboard i2c header and easy cable option for a screen. I don't know if people would want a screen, I can't see why not though.

Though if I make my own board, any of the micros could plug in easily and I could put on my own header for screen.

I can include the ability to have the output shown on a PLX gauge as well, simply because I will be doing this myself anyway. Also because of what I will be doing myself, it could potentially read datalogs from the ECU put them on the screen and/or plx gauge. Not really the main focus but I thought I'd mention it in case anyone is interested.

forbiddenera

Not sure I love the idea of having to have an FTDI cable to program it. While I can pre-program kits for people, if based off that micro, it would make it difficult for the more average user to be able to program the device.

Also if someone did buy a programmed kit, and there was an update down the line that they wanted it would be more difficult for them to program.

The ProMicro 32u4 5v/16mhz could be an option. I don't think it has any eeprom though. Only takes upto 12v. Has on board USB though, so can be used as a usb device; I use it for using my keyboard and mouse in ps4 games, the ps4 sees a USB controller, the other side of the device is hooked to my pc through an ftdi that sends my kb/mouse inputs to the ps4. Neat little trick. It's about $20 though.



https://www.sparkfun.com/products/12923

This is an interesting display with built in controller.. only 64x48.. but has a 5v 328 built in.. It's like $50 though..but could plug right into a small board I make with connectors to break out and done..? I would have to have an ftdi on my board and usb to make it programmable though. They do have USB programmer board for $15.. Neat idea, could work, but I don't like the small resolution of the display

forbiddenera

The teensy 4.0 could be an overkill option. 2mb flash with eeprom emulation, 2 usb2 ports, 3 canbus, 2 i2s, 1spdif, 1sdio, 3spi, 3 i2c, 7 serial, 32 dma, 31 pwm, 40 digital, 14 analog w/ 2adcs, crypto/rng, rtc, pixel proccessing, pwr management..
$20

3.6 a little less nuts.. still has canbus.. has on board microsd port. $35 though..

why can't I find what I want for like $1 then? (without ordering from ali).. 8bit micro vs 32bit.. both are around same price.. sigh.

although really if I'm making my own board I could just throw a micro on it.. but that's a lot more complex undertaking than a board with like 2 traces for a capacitor and resistor and some plugs..

I think I still more like the idea of just plugging in an arduino style controller, plugging in the plugs, and go..

forbiddenera

I could just use one of those boards schematics as a starting point. But I am sure as hell not soldering smd parts for people, so they'd have to get assembled by whatever pcb place I use. Don't know how much more that would be. I like the idea of a plug-in board because it's simple and people don't really need it anyway, they can just add the Rc circuit on their own

forbiddenera

Okay, Eagle sucks. Only thought I'd try it because I didn't have any pcb tools installed right now and the files for the boards were in that format. What a pain. I can't even get it to let me move my parts around the board without having to type in their coordinates. Will try something better tomorrow.

But I got a basic schematic started. Sensor plug puts out +12v and gnd for sensor and receives input from sensor. Other plug is 4pin for +12v, gnd, and the two 5v outputs. This currently has a jumper to let you power the micro from +12v, or you could provide it from usb. Although I might throw on some sort of regulator, it would have to be buckboost or else it's not really any better than the LDO on the micro board.

extremeracer

I think if you could sell an affordable kit with a screen with basic insulated connectors there would be a market for most of the 'amateur-level' tuner cars. I'd offer one kit with a screen (I like the rectangular 'widescreen' one) and one version without a screen and just an output to an ECU.

The soldering of electronic boards is not something most DIY mechanics/enthusiasts are comfortable with - so a plug-and-play option I would think would be most appealing.

Thanks for doing all this work though - it looks very promising.

forbiddenera

thanks

this one popped up on my phone today..has a screen right on the board. Might be an option

https://www.tindie.com/products/ttgo...-display-gd32/

have to look closer at the specs later but I think having the screen separate might be better still although that screen looks like it might be half decent. Never know until you see it.

​​​​might order one of those too.

and yeah some sort of solderless kit will be an option

forbiddenera

Went to the local electronics shop and spent a few hundred on parts for this project and others I have on the go

- adjustable buck regulator for powering the unit (optional but recommended)
- a 2nd identical screen to sell with the first kit
- a generic case that should fit it
​​​​​​
just need some microcontrollers. I looked at the local options and will probably just order some.

I am also working on a few other projects related to this:
- building an ECU simulator for testing
- porting a p28 reverse engineered circuit chematic I was given to modern schematic/circuit software (I will make this public)
​​​​​​- learning 66k assembler and instructions and trying to setup a tool chain so I can..
- re-code the HTS flex fuel implementation to scale primary and secondary map values based on ethanol. Basically primary table is 0%-10% ethanol and the secondary table is 85-98% and it will just blend between them.

that IMHO is a better implementation than exists for our ecus currently. All others just give you a few columns of compensation of for and ignition for ethanol percent. It works but is rudimentary..my method is more.similar to standalones and shouldnt (I'm hoping) be overly difficult to implement.
​​​​​​
​​​​​I do have the source code required so it's just time and knowledge
​​​​​
I'm partially not sure whether I want to wait for my.implementation to do flex fuel or not. I may do it anyway but I haven't wanted to install the sensor yet so I can still have it ready for testing.

I don't think the status my projects or whether my preferred implementation is available should affect this project; I will order microcontrollers this week and I will try and get a 2nd flex fuel sensor for testing with next time I go to junk yard.

Once I have the controllers I will put the first kit together, probably with a video or at least photo instructions as well as the source code. Once that first kit is built, it will be available for whoever wants it. Of course people can also acquire the parts and do it themselves.

I'm still seriously considering making a carrier board with good connectors and the filters onboard..this may be available in the first version but would likely be a generic prototype/perf type. If there's enough interest and i have time I will lay out a custom board and order some.

​​​
​​​

DaX

iTrader: (1)

Do you have the schematic from Bomarc Services? I've had a copy of that stashed for a long time.