Freematics Forum

Hi I'm wondering how you guys are determining and interpreting the OBDII protocols. I just noticed there was not a lot out of open stuff out there for decoding and determining RAW OBDII data and I want to build my own OBDII decoder from scratch. Did you guys use an ELM327 or STN1110 or developed your own algorithm? Is that what the STM32 MCU on the Freematics OBD-II Adapter does? Was your own code written on that to decode it? Sorry for all the questions, any help would be really appreciated.

We have our implementation and it is done with the onboard STM32 processor.

Is it alright if I ask more on your implementation? The test vehicles are my friend's '00 Ford Focus (PWM) and my '09 Nissan Sentra (CAN) currently using an Arduino Due and OBD cable with what seem to be an ELM327 chip or the ELM commands in some form as a way to check if our system is working. How were you able to understand what the raw data from the vehicle means? Seems like a lot of that is manufacturer specific, especially the DTCs. I see your "elm327emu.ino", but does not seem to do much other than spit out what something it read from the STM32 I assume?

There are two protocols for Ford:

1) legislated - SAE J1850 PWM which is not supported by the Freematics OBD - II Adapter's 32-bit protocol processor (CAN, KWP2000, ISO9141-2)

and

2) non legislated - Medium Speed CAN (MS-CAN) – Ford proprietary network. I'm not sure if the Freematics OBD - II Adapter's 32-bit protocol processor (CAN, KWP2000, ISO9141-2) can support MS-CAN.


I know this hardware is open source so it might be possible to add more protocols to the 32-bit protocol processor (CAN, KWP2000, ISO9141-2)? I have a Cadillac and Mustang and would be interested in adding SAE J1850 VPW (GM vehicles), Single Wire CAN (SW-CAN) – GM proprietary network, SAE J1850 PWM (Ford vehicles), and Medium Speed CAN (MS-CAN) – Ford proprietary network.

I also read somewhere that there is an issue with requesting information using ELM327 strings because the Freematics OBD - II Adapter outputs binary.

Technically we can add J1850 support but this adds a lot of cost and will probably increase the enclosure size. So we didn't include it. For proprietary protocols, I am sorry we didn't spend any time on this.

Have you thought about using the STTN1170 chip in the Freematics OBD II adapter? http://www.obdsol.com/solutions/chips/stn1170/

We will NEVER use products from this company.

stanley wrote:Technically we can add J1850 support but this adds a lot of cost and will probably increase the enclosure size. So we didn't include it. For proprietary protocols, I am sorry we didn't spend any time on this.

Hi Stanley,

could you elaborate on "more costs" and "increase the enclosure"? Does it mean that the hardware would need to be redesigned? Wouldn't it be more simple to just read out raw binary information and send via BT then decode the received raw data via a computer?

Is the decoder code for the STM32 available?

Black6spdZ wrote:Is the decoder code for the STM32 available?

that's an interesting question.
the decoder code could be useful