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[on:]

Hey guys finally bought my first arduino and i want to interface it withmy nissan 200sx (240sx in th US). I've done a little research on the communication between the two sofware wise, but i'm having a little difficulty with the hardware. The ecu uses12v for comms but the arduino obviously only uses 5v ttl. Can i use a resistor divider to drap the 12v signal so i can read it using the arduino? And how do i step up my 5v signal to 12v for transmitting to the ecu?

Thanks in advance guys

[Reply #1 on:]

What kind of communications do you plan to do? Is it CAN, OBDII? RS232? Do you know the protocol?

[Reply #2 on:]

its none of the above. check out the link for clarification;
http://www.plmsdevelopments.com/images_ms/Consult_Protocol_&_Commands_Issue_6.pdf

i think i've got most of the communications worked out as far as software goes, i just need to know how to convert the tx signal from the ecu down to a 5v signal so the arduino can read it, and convert the 5v ttl tx from the arduino to a 12v signal so the ecu can accept the commands i send it.

[Reply #3 on:]

To convert from TTL to RS232 you need a MAX232 chip.. If you want to save yourself some work, http://www.ebay.com/itm/RS232-Shield-Arduino-/270801572459  here's an RS232 shield.

[Reply #4 on:]

um pretty sure its not RS232. but i could be wrong seeing as i'm a relative noob when it comes to comms.

[Reply #5 on:]

actually after reading a little on the net, could i use an RS232 or MAX232 ic to convert the signal? will the -12v output cause a problem or is there a way to bias the ic to only output 0v-12v to the ecu instead of -12v to +12v?

[Reply #6 on:]

Why not use a Bluetooth/RS232 device attached to aduino and the attach a Bluetooth ODBII device... like ELM327... Arduino adapter usually runs about $6  and the ELM327 runs about $24 and you end up with a nice wireless solution.  I much prefer that to having wires near my legs and feet while driving.

[Reply #7 on:]

the 40x4 display will actually be mounted in the dash and the consult plug is hidden inside the kick panel so even if i was going to use a consult plug instead of wiring into the loom, there would be no wires hanging around. it'll all be routed up through the underside of the dash. that and adding wireless to cover a 30cm gap seems like a lot of overkill to me. also, the elm327 would be pointless as its a consult interface, not obdII. completely different. i'd rather get some help to figure out how to convert the signals to be readable both ends. i don't just want to make it work, i'm also hoping to learn a little bit as i'm doing it as well.

[Reply #8 on:]

Will this work or will the transistor not be able to keep up? or are there other issues i'm not seeing?

[Reply #9 on:]

Looks good to me but suck it and see -not much to making it up on a breadboard

[Reply #10 on:]

TX data to ECU level is 12V, idle low (see interface schematic). ECU output is
open collector and can be sourced from the interface logic level (5 V). The ECU
data output is idle high.

Thats from the info i have found on the net about the consult protocol. does that mean that i shouldn't have a 10k pull-up between the transistor and the ecu RX pin? because that would make it idle high instead of idle low like it should be yeah?

[Reply #11 on:]

nobody knows?

[Reply #12 on:]

my schematic so far if anyone has any useful info to add or any problems that can be seen?