[Ovmsdev] Volt/Ampera CAN Logs

Mark Webb-Johnson mark at webb-johnson.net
Fri Jun 1 09:11:55 HKT 2012


Thanks for this. Most useful. I'll see what I can do with Michael (who is working on the development of the Volt/Ampera can module for OVMS).

Do you have any logs that you can share (either privately with Michael and myself, or publicly)? In particular, I'm interested in those messages I mentioned. It would be useful to be able to use this for validation of what we're doing and comparison. Don't worry about the format. Any textual fomat is ok - I'll convert it to the can-re-tool format. My eMail is mark at webb-johnson.net.

The GPS issue is worrying, but not overly so. At the moment, OVMS uses a SIM900 chip for GSM/GPRS. As we are looking to support more and more cars, and realise that most don't have GPS systems on the CAN bus, we've been looking to switch to the SIM908 chip which also has GPS onboard (accessed via the same async port and AT commands as the GSM/GPRS system). If necessary, we can use that, but let's see what Michael comes up with when he manages to log more data.

For charging, I would suspect that the charge mode (charging or not) is in there somewhere.

Have you looked at what is logged when the ignition is off? Michael sees that all messages stop, and we are concerned that will mean an inability to monitor charging. I think for your project, you are more concerned with monitoring driving, so not an issue for you, but interested in what you've found logging what the car does during charging.

Regards, Mark.

On 31 May, 2012, at 9:34 PM, R. Scott Perry wrote:

> Hi everyone,
> I'm the RScott from gm-volt.com, and I wrote the page at evtools.info about the Volt and OBD2 data (which I haven't updated in quite some time).  I've read the recent posts to the list about the Volt, and thought I would provide information here in response.
> First, if it would be helpful, I have written a program for Windows to record data from an OBD2 scanner.  It is designed to work with scanners that use the ELM327 chip (or are compatible).  It saves the timestamp, and saves the data in the format "11:48:45.829: 206 639600".  It is run from a command prompt, and not very user friendly.
> For the SOC, the "206 3 69 C3 00" capture indicates CAN ID 206, with 3 bytes of data.  The SOC data only uses the first two bytes, so this would be 0x69C3, or 27075d.  Dividing by 4,000 gets 6.769kWh in the battery, or about 42% of the total battery capacity, which should be 4 bars on the display. http://gm-volt.com/forum/showthread.php?5328-Volt-Diagnostic-Tool&p=91868#post91868 correlates the SOC number here with the bars displayed.
> The VIN can be constructed by taking the number "1" and converting the CAN IDs 4E9 and 514 to ASCII.  So with "4E1 4255313032363839" and "514 4731524436453436", you would end up with 42 55 31 30 32 36 38 39 47 31 52 44 36 45 34 36, where 42 is ASCII for B, 55 is U, etc.
> The latitude/longitude conversion is almost the same as what you have for the Tesla, with two exceptions -- changing the 2048 to 1000, as noted, and the accounting for negative numbers is different.  It seems that the number the Volt supplies is a 31-bit signed integer.  The easiest way to handle that, I think, would be to add "latlon = latlon << 1;" before checking for <0, and then "latlon = latlon >> 1;" afterwards.  Running the code you have with those two changes seems to work fine.
> The bad news is that I have checked all my log files (I have been logging almost all the time I have driven for about 8 months now), and the CAN ID 32A (latitude/longitude) has never shown all zeroes.  If the GPS data is unobtainable, I believe the car reports the most recent reading.  The GPS data comes from the OnStar system, so I am thinking it may only provide the data if the OnStar service has been activated, which could be a problem for owners outside of U.S/Canada.
> For charging, all I have found so far are some numbers that appear to show electricity flow to/from the battery.  If they are positive, electricity is going to the battery; if negative, electricity is leaving the battery.  But this will also be positive if the gas engine is on and charging the battery, as well as if the car is going downhill and the regenerative braking is being used.
>                       -Scott
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