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+---- Thread: USB K+DCAN Baudrates (/showthread.php?tid=15226)
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USB K+DCAN Baudrates - targa9 - 27-04-2016
This may be common knowledge to a lot of people on here but I thought it might be worth sharing my findings.
In summary I find configuring a USB K+DCAN lead works when set to 115,200 baud, no parity, 8 bits, 1 stop bit and all the buffer and latency settings at their minimum – but not reliably on all cars.
I have a suspicion that some protocols are only 100k baud so this might be too fast. Anyway yesterday I found out that was the case. On a 2002 E46 318i the ISTA-D comms almost identified the car then dropped out just before moving on to the error codes. To rectify the problem I set the baud to 38400 and it worked perfectly (57600 probably would have been OK but I didn’t try it).
What scares me was that ISTA-P seemed to be working at 115200 baud but I suspect it may have encountered the same problem when it came to actually programming something.
So my conclusion here is that if you’re using a K+DCAN lead on a variety of cars, some back the early OBD2 (around 2002), then use a baudrate of 57600 or slower.
A switchable USB K+DCAN lead also has an interesting capability I hadn’t expected:
Switched so the K lines are linked together it’s good for cars around 2003 - 2007
Switched so there’s a DCAN and K line it’s good for cars around 2007 - 2010
Switched so there’s a DCAN and K line it’s good for cars before 2003
For the record I’m running:
Windows 10 Home 64-bit
ISTA-P Loader V4.8
ISTA-P 3.57.4.003
ISTA-D 3.47.30
RE: USB K+DCAN Baudrates - beemerboy88 - 27-04-2016
Try these settings:
Bits per second - 9600
Data bits - 8
Parity - None
Stop bits - 1
Flow control - None
Receive - 4096
Send - 4096
Latency timer - 1
RE: USB K+DCAN Baudrates - targa9 - 27-04-2016
Thank you for the feedback.
I always ran DIS57 at 9600 baud. When I moved up to ISTA-D I experimented with a 2004 dual K line car quite a bit although I didn't time anything. I'm fair sure the the time to interrogate all the modules dramatically improved as I increased the baud rates from 9600, and on that car I couldn't "break" the comms even using 115,200 baud.
In fact 115,200 baud has been fine (I think) on everything until I needed to work on an older car.
Now I appreciate you *really* know what you're talking about but I am better off with a really slow baud rate and a 4096 byte buffer? Those big buffers scare me. My experience with INPA, DIS etc. is the smaller the buffer the better (you're just making the PC work harder). I don't know the car protocols at all but I sort of expect the packets to be small and therefore with a larger buffer the responses could get queued?
I'm also sort of aware that the majority of the serious players on this forum will be using ICOM so this is a bit of niche for this forum but it would very handy to fully understand what the ideal (fastest yet safest) settings would be.
RE: USB K+DCAN Baudrates - Node - 27-04-2016
Do you guys realize that OBD adapter driver (within Ediabas) changes the baudrate automatically according to the protocol used by different units? So baudrate change in windows does not matter at all. What matters are USB-COM converter latency settings which actually mean how long USB driver waits before submitting data to the converter. On normal (hardware) COM ports there are no such settings as each byte is transmitted as soon as possible. USB drivers on the other hand wait for some time to collect more data and send them in bulk hence your connectivity issues. You should invest into normal hardware COM port if you want clean communications. Or alternatively, ICOM.
RE: USB K+DCAN Baudrates - targa9 - 27-04-2016
(27-04-2016, 15:46 PM)Node Wrote: Do you guys realize that OBD adapter driver (within Ediabas) changes the baudrate automatically according to the protocol used by different units? So baudrate change in windows does not matter at all. What matters are USB-COM converter latency settings which actually mean how long USB driver waits before submitting data to the converter. On normal (hardware) COM ports there are no such settings as each byte is transmitted as soon as possible. USB drivers on the other hand wait for some time to collect more data and send them in bulk hence your connectivity issues. You should invest into normal hardware COM port if you want clean communications. Or alternatively, ICOM.
That's sort of what I expected at the start...but I 100% found that on an E46 a baud rate of 115,200 didn't work but 38,400 did. I went back and forwards and didn't change any other parameters.
I'm also pretty sure ISTA-D ran a lot faster at 115,200 baud although I'm starting to doubt myself now.
A bit of research after Beemerboy's response tells me that underlying on most of the cars before DCAN the OBDII protocol runs at a maximum 10.4k bits/s so matching the baud rate to 9600 would make sense.
However if the baud rate does affect the comms then D CAN cars would be better with 115,200 baud.
I only do a bit of diagnostics (and potentially programming) for myself, friends and occasionally the local garage so ICOM is a bit of a luxury.
RE: USB K+DCAN Baudrates - Node - 27-04-2016
Well, if baudrate change in windows settings affects your car communications, then the only thing I can think of is that your USB-COM converted is a crap.
RE: USB K+DCAN Baudrates - stmilosh - 28-04-2016
(27-04-2016, 16:08 PM)Node Wrote: Well, if baudrate change in windows settings affects your car communications, then the only thing I can think of is that your USB-COM converted is a crap.99.9% of USB-COM adapters use the very same FTDI FT232R, so I really don't see how that can be crap on some, and great on others.
RE: USB K+DCAN Baudrates - doktorabg - 28-04-2016
If you have many FTDI drivers than comes conflict.
Use FTCLEAN. EXE and install again one by one.
Here is the rights setup of BMW USB K+DCAN with right driver.
RE: USB K+DCAN Baudrates - stmilosh - 28-04-2016
(28-04-2016, 19:23 PM)doktorabg Wrote: If you have many FTDI drivers than comes conflict.
Use FTCLEAN. EXE and install again one by one.
Here is the rights setup of BMW USB K+DCAN with right driver.
The best drivers are the newest drivers from the USB-COM chip manufacturer.
There is no such thing as BMW drivers.
Currently the latest is 2.12.16 and could be downloaded from the manufacturer page.
FTClean is also a nice tool and is official from FTDI. FTDI removed the link on it from the Utilities page, but the tool is still there
.
RE: USB K+DCAN Baudrates - doktorabg - 29-04-2016
(28-04-2016, 21:03 PM)stmilosh Wrote:(28-04-2016, 19:23 PM)doktorabg Wrote: If you have many FTDI drivers than comes conflict.
Use FTCLEAN. EXE and install again one by one.
Here is the rights setup of BMW USB K+DCAN with right driver.
The best drivers are the newest drivers from the USB-COM chip manufacturer.
There is no such thing as BMW drivers.
Currently the latest is 2.12.16 and could be downloaded from the manufacturer page.
FTClean is also a nice tool and is official from FTDI. FTDI removed the link on it from the Utilities page, but the tool is still there
Hey , I don't say that there is BMW DRIVERS!
I say that if you have many FTDI drivers install in PC than comes the problem for K+DCAN like latency timer is set to 16 and not to 1and another settings to and you must manuell make it.
On fresh install you become the rights settings like on pictures, look it carefully!