VR, Resets, DR650 Toothed Wheel

[2wrider]

I working with the new V3.0 squirt, and I'm experiencing resets when I hitch up the VR sensor to the squirt.

Now, for the interesting part: I've written code to sync up with a Suzuki DR650 using its rotor's stock tooth arrangement. The code samples the VR1 signal, obtains sync, and uses the squirt's ignition 2 as an signal output so I can see how the VR1 input filtering circuit is working. I've attached a trace below showing the VR output from the sensor in blue, and the sampled input (sent out through ign 2 for monitoring) in red.

dr650_vr_small.jpg

DR650 VR with sampled output

(115.33 KiB) Not downloaded yet

I'm running the squirt off a bench DC power supply at around 14V, and I have the rotor mounted on a board sitting on the starter gear where I spin it with a drill -- yep very high tech it is, very high tech. All works well when at a steady speed, but slowing down fast and starting up often causes resets. I tried using a hall sensor (I tried both the VR and option inputs), and I get the same results.

Anything interesting I could try to find the problem?

Marty

[dontz125]

Can you post your .msq and a pic of the wheel?

[2wrider]

No .msq file as I'm not running the stock code. The test is limited to the VR1 circuit which past the new V3.0 filtering stuff is pretty much just an input compare timer hanging around waiting for rising and falling edges. Well, a bit more, but not much. From the oscilloscope trace, I can see that's all working just fine, You can see the geometry of the wheel in the trace. It's one long tooth (3x), small gap (1x), small tooth (2x), large gap (24x). Everything seems to be working just fine, save for those pesky resets.

[dontz125]

Yeah ... zero-crossing VR circuits REALLY don't like long teeth. See this page from the MegaManual for more info - the part you'll be interested in (but still not liking) is about halfway down.

If you're just trying to establish a pattern that the uS can learn and recognise, perhaps a going-positive edge-detection circuit as a pre-filter can feed the VR circuit. Every leading edge of a tooth will send a trigger pulse.

[2wrider]

Yep, I've read that section, but I get what looks to be a nice edge detection even with a VR sensor. The point you mentioned made me nervous, but my trace showed pretty good results. Though even if I had issues with the VR sensor, I could still use a hall sensor for better edge detection. I'll have to see how that goes along the way.

I think my reset issue may have to due with the fact I hitched up an oscilloscope to the circuit. It does not have a floating ground like a good ol' DVM. I'm not sure yet though.

Interestingly, the VR1 circuit doesn't see anything from my hall sensor, if I don't have my oscilloscope, and it's ground hitched up.

[dontz125]

I can't comment on the silly-scope; I really have no experience there. I do know that many hall sensors need a pull-up resistor, since the 'switch' inside is just a transistor dumping to ground when triggered. No pull-up, no +5 or +12v square-wave signal.

I really am surprised the long tooth isn't causing more issues. Wheel teeth of 36deg and 24deg should both be giving that VR conditioning circuit absolute fits! The older GSXR wheel teeth are 36/5/5/5, and it took an adaptor circuit and custom code for a fellow to get a clean read out of it ...

[2wrider]

Found the problem. The VR- input was loose in my terminal strip. It was somehow causing fits to the squirt.

For those who are interested:
I'm running a Cherry GS100701 hall sensor. With a 3K pullup as recommend by the manufacturer for the voltage I'm running.

Vcc is same as for the squirt at 14V. Sensor ground connected to main ground. Sensor output to squirt's VR+. VR- not connected.
No more resets!

The squirt's VR1 conditioning circuit is quite happy with the DR650's funky tooth geometry; just a bunch of edges to it.

Here's a pic of hall sensor trace (read from VR1 and mirrored to ignition 2):

d650_hall_small.jpg

(106.34 KiB) Not downloaded yet

Marty

[dontz125]

Now THAT is a nice clean trace!

Disregard what I was saying about long teeth - I saw that you were using a Hall sensor, even commented on it! I got sidetracked though by the letters "VR" ...