OBD MPGuino gauge

[DJ_SpaRky]

That is r135 and it is up to r187 now. try this page:

code.google.com/p/opengauge/source/browse/#svn%2Ftrunk%2Fobduino32K

[Bix]

Also i'm running a toyota corolla 2002, the obd plug has other inputs besides the power, ground and k line. It doesn't have any pin at #15 but it has a pin at 6 and a pin at 9, both showing around 11 volts, not sure what they're used for.

Also my K line just gives a constant 11.1 volts to my multimeter, other people said it was supposed to fluctuate, is there something wrong or is my multimeter too crap?

[DJ_SpaRky]

This page shows that #15 is the L-Line, but #6 for CAN & #9 is Manufacturer specified, so it could be anything. Make sure that you are count the pins the correct way. My Toyota based car has a pin in #1, #4, #5, #7, #15, & #16, some are not used for this device.

OBDII - On-Board Diagnostic's System - Does My Car Have OBD-II? The Connector and Communications.

[njakts]

I have a feeling I am missing something
first - I had obd2 reader laying around, that uses bluetooth for communication. I opened it up and noticed that it is using this exact circuit apart there is some Pic microcontroller in the place of ELM chip, could this pic be ELM's replica?:

but the Tx Rx lines are connected to bluetooth module. so I pulled out the bluetooth module and connected TxRx to arduino. took it to car, connected but it only shows Obduino security, a * is bouncing around and Rx light on the OBD reader blinks several times.
So arduino is trying to communicate, but does not hear any answer (tried to swap rx and tx pins, no use)? then the problem must be the replica of ELM chip.

second - had a look at my cars wiring and found out that OBD is using pins 4 and 5 and of course 16 for power then there is Pin 7 - ISO 9141-2 K Line, Pin 13, and Pin 14 - CAN Low (J-2284). and there is no Pin 15.

since the pin 7 is present, I can deffo say that my car has ISO protocol?
the car is year 2000 Lexus IS200.

third - since my car uses ISO protocol I can make this circuit and it should work?

schlorkist's image

and fourth - how is the communication happening? why it is showing this obduino security?
when it will go off?

[Magister]

We do not know the PIC part number, maybe it's a 3.3V one so the TX/RX is not the same level as the ATMEGA.

You should be able to replace the MC33290 with a circuit using two transistors or one like yours, yes.

[njakts]

thanks!
the chip is PIC18F2480-1 and it is using 5.0v supply.

than ill try to make that MC33290 replica

[njakts]

my God! I am starting to give up
did the voltage comparator circuit twice, or three times - nothing.
did the circuit with two transistors - nothing!
All i get is Obduino security and a bouncing * icon.
MPGuino worked fine on that same Arduino Duemilanove

[Magister]

Have you try 14230 protocol?

[njakts]

what must be done to try 14230 protocol?
I am quite dumb in software level. I have no idea how the program works

[gone.s2]

Originally Posted by njakts

what must be done to try 14230 protocol?
I am quite dumb in software level. I have no idea how the program works

I hope you haven't given up. It appears there's an OBDuino support drought recently.

You'll need to take a look in the source and find the following code:

// Uncomment only one of the below init sequences if using ISO
#define ISO_9141
//#define ISO_14230_fast
//#define ISO_14230_slow

This is the default configuration in trunk - iso9141. To try the other protocols place a single line comment (two foreslashes) in front of the #define ISO_9141 and remove the comment from one of the other two to try a different iso protocol. Upload to your atmega and give each protocol a try.

Also, if you're using schlorkist's voltage comparator circuit, I found that a small revision was necessary in order for switching of the RX side, this could very well be your issue also. I had to remove the interconnect from pin 6 to pin 5 and create a separate voltage divider that floats this input closer to 3 volts (I had a 4.1k and a 12k resistor handy, which happened to work). If you're not sure what I'm getting at here don't hesitate to ask and I'll try to draw up a schematic.

An easy way to test whether the RX comparator channel is functioning properly is to use a multimeter and watch the output of the LM339 channel 2 (pin 1). If it's at or near 0 volts the majority of the time you have the same problem I did. When the voltage divider is right you will see the output of channel 2 hover around 5 volts most of the time and then pulse near 0v when the iso init routine sends the 5 baud request. This should happen in unison with the K-Line output on the collector of Q1 (measure on pin 7 of the LM339). I'm not sure if this is a flaw in schlorkist's design, or possibly a difference in comparator sensitivity. I wonder if he would care to chime in about this in case he made revisions to the circuit that weren't posted.