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I have a Bluetooth ELM327 adapter that I am using with my car's OBD2 port. I have an Arduino UNO compatible Magpie (Little Bird Electronics) which I would like to use to interface with this adapter.

My current idea is to solder two wires onto the RX/TX lines (If they exist/can be found) or to connect to another component.

The PCB, from what I can find has:

  1. A Beken BK3231 bluetooth chip (Appears to be QFN36?), running off a 16MHz crystal (Best guess from text on top - P16 00M N FAB C)
  2. An unnamed 8 pin chip which connects to OBD2 pins 3 and 11, GND and another two pins off to the processor (Which I suspect might be TX/RX?). From what I can tell the rest of the pins go either to ground or power.
  3. An ELM327 processor under a heatsink blob (At least that's what I think those big black circles are?), which is not accessible for soldering.
  4. A chip labelled 8A825 which I suspect is a voltage regulator.

From this, what what would appear to be the best option for attempting to allow the Arduino to hook into this PCB and/or if anyone has any suggestions as to which pins might be a good place to start for TX/RX or other data protocols (UART/SPI/I2C)? I'm just starting out and wanting an opinion before I go and solder to something I shouldn't or completely stuff the PCB.

EDIT - The board

Bottom right is 8A825, top right is BK3231, middle is the serial converter?

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    \$\begingroup\$ A typical bluetooth ELM327 is just a odb to serial and a serial to bluetooth adaptor so your on the right road. You just need the TX and RX lines. But for simplicities sake, a cheap bluetooth adapter for your arduino would be just as easy. Hc05 for example. \$\endgroup\$
    – Passerby
    Dec 21, 2015 at 17:37
  • \$\begingroup\$ Also please post a good clear picture of the board. \$\endgroup\$
    – Passerby
    Dec 21, 2015 at 17:42
  • \$\begingroup\$ @Passerby updated, cheers. \$\endgroup\$ Dec 21, 2015 at 21:46
  • \$\begingroup\$ This unit doesn't have an elm327 chip. The can converter chip is a OnSemi NCV7342 CAN transceiver. \$\endgroup\$
    – user116424
    Jul 11, 2016 at 13:22

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This PWA does not have a true ELM327 chip but there is a Microprocessor under the black CoB blob. This is (more than likely) a copy of the ELM327 v1.0 software with the version data changed to spoof a later version (ELM did not copy protect their first version of the software, but did in later versions after someone copied out their code). The connections would depend on what you are trying to connect to. There are 2 TX/RX sets, one is after the 8 pin chip as it converts the Vehicles CANbus into RX/TX for the ELM327 clone, the other is the data from the ELM327 that is being transmitted and received from your Bluetooth device (this I suspect is actually I2C and is on the 2 traces that go from the black blob to under the BK3231.

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