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Title: newbie - first question - dumb k-line interface init Post by: Dakta on October 18, 2012, 06:11:32 PM Hi everyone, been lurking on here for about a week or two, i've never seen a board like it, jam packed with information. Good stuff.
Just wondering if anyone could offer some quick advice regarding the old vag com (or dumb k-line) interface - i'm using it as a level shifter allowing me to send frames through the k-line to the ecu, and receive responses straight to my serial port. It's good for monitoring (or hijacking even) existing connections, but I'm not sure how to initialise a connection. I need to emulate a kwp-fast init for my particular ecu, i'm not sure how to do the initial 25ms low and 25ms high k-line activity before transmitting any necessary wakeup messages. Is it possible with these interfaces (probably a simple answer but it's got me foxxed!). cheers Kris Title: Re: newbie - first question - dumb k-line interface init Post by: prj on October 19, 2012, 01:56:00 AM Hi,
I have not done fast init, but slow init goes like this: Code: void initcomms() {I imagine you can do fast init the same way via bit banging. Title: Re: newbie - first question - dumb k-line interface init Post by: Dakta on October 19, 2012, 09:16:32 AM You know what, that is a REALLY good idea!
I use vb.net myself (do a bit of microcontroller coding in c, but i'm no great shakes at it yet) - I didn't realise we could bit bang from this high a level, but it looks like we can use the break 'feature' - this is brilliant stuff. Thank you. What a forum. Title: Re: newbie - first question - dumb k-line interface init Post by: Dakta on January 06, 2013, 05:11:13 PM Just wondering if there is anything else I could try?
I've tried the breakstate technique - but the ecu doesn't respond, i've monitored diagnostic tools that perform the init with a k-line serial converter and the same start communication message is sent as my own, so I can only conclude the problem is in the wake up signal (25ms low, 25ms high) timing. I do a breakstate then sleep the program for 25ms each. I write the software in vb.net so i first tried a timer, later learnt this isn't very accurate so used the stopwatch which is considered very accurate - however no improvement. I also read that sending 0x00 at 360 baud can also simulate the fast-init 25ms low signal but that didn't help either :( I'm sure i'm sending the right data, but i don't have an oscilloscope to see whats happening at a signal level think ill have to get one, won't give me an answer but might confirm if it is a timing issue which it has to be really because I get a positive response if i set my elmscan to the same headers and send a start communication message exactly the same contents as my own. Title: Re: newbie - first question - dumb k-line interface init Post by: prj on January 07, 2013, 01:32:49 AM Well, you answered your own question.
The only thing I do is use timeBeginPeriod as well. Title: Re: newbie - first question - dumb k-line interface init Post by: Dakta on January 07, 2013, 03:27:44 AM Unfortunately I think I did!
I'm being tight, it's the wrong month to spend on a scope! but i see no alternative Title: Re: newbie - first question - dumb k-line interface init Post by: prj on January 07, 2013, 03:36:43 AM Yeah, I guess not...
I was luckier and the code I wrote worked the first time :) Title: Re: newbie - first question - dumb k-line interface init Post by: Dakta on January 07, 2013, 04:11:47 AM I can't see anything else anyway, i'm using the most accurate timer I can find in the vb.net arsenal, the right startcommunication request and I do let the kline idle 300ms before trying to start a connection so looks like it's time to be poor :P
do appreciate the guidance Title: Re: newbie - first question - dumb k-line interface init Post by: prj on January 20, 2013, 01:34:47 PM Well, I did not try fast init, but slow init goes like this:
void slowInit(unsigned char address) { unsigned long len = 128; // The K-Line must be high for at least 300ms DeviceIoControl(comport, IOCTL_SERIAL_SET_BREAK_OFF, NULL, 0, NULL, 0, &len, NULL); Sleep(300); DeviceIoControl(comport, IOCTL_SERIAL_SET_BREAK_ON, NULL, 0, NULL, 0, &len, NULL); // Start bit (low) Sleep(200); for (UINT i = 0; i < 8; i++) { if (((0x01 << i) & address) > 0) { DeviceIoControl(comport, IOCTL_SERIAL_SET_BREAK_OFF, NULL, 0, NULL, 0, &len, NULL); // 1 } else { DeviceIoControl(comport, IOCTL_SERIAL_SET_BREAK_ON, NULL, 0, NULL, 0, &len, NULL); // 0 } Sleep(200); } DeviceIoControl(comport, IOCTL_SERIAL_SET_BREAK_OFF, NULL, 0, NULL, 0, &len, NULL); } Works just fine for KWP2000 too, use address 0x11. |