Incorrect Engine RPM over ODB2?

[Tobe Determined]

Hi all.  Experienced EE here but new to OpenXC (sorry).  I have a Nexus 7 Gen 2 (2013) connected to a Digilent chipKIT-based VI connected to a 2013 Ford Flex's ODB-II port.  I followed the online tutorial and flashed my chipKIT with "vi-obd2-firmware-CHIPKIT-ctv7.0.0.hex"  All seems well and I get Engine RPM and Vehicle Speed updating at about 1Hz on the Nexus display, however the engine RPM is off by about 1500RPM.  My Ford Flex idles at around 500RPM per the in-dash gauge, however the OpenXC display shows ~2000RPM.  Any ideas?  Thank you!  -T

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keywords to help others searching for a similar questions/solution: wrong bogus offset invalid engine RPM RPMs ODB2 ODBII ODB-II

[Christopher Peplin]

Hey there, interesting find!

The calculate for the engine RPM PID is here: https://github.com/openxc/uds-c/blob/master/src/uds/uds.c#L296

It seems right to me, according to the wiki page for PIDs: http://en.wikipedia.org/wiki/OBD-II_PIDs#Mode_01

but I don't doubt that there could be a bug somewhere in the pipeline of CAN message reading through to the translation and output. Either that, or there's something different about that PID on the Flex. I did verify this once a while back on a Mustang, and I don't recall seeing such a discrepancy.

Anyone else ever compared the RPM value from the OBD-II build?

Chris

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[Travis Gintz]

I also noticed an issue as well with 7.0. I haven't used any previous firmwares as I just got my C5 from Crosschasm. I used the C5 firmware.

I loaded vi-obd2-firmware-CROSSCHASM_C5..... and noticed that RPM was WAY off. I loaded vi-translated_obd2-firmware-CROSSCHASM_C5 and it worked just fine. 

I haven't had much time this summer to play with it any more past that.