VSS limit

[t vago]

Originally Posted by alexander.foti

I would say thats the issue as well, although I would like somebody who is experienced with the code to let me know if it is.

Surely I can just use a freq divider on the VSS signal to keep it seperate from the mpguino? Im no good with IDE like the arduino, and OK with electronics (if following instructions )

With 120,000 pulses per mile, and going 78 MPH, your MPGuino is seeing a pulse about every 385 microseconds. That's about the time needed for the MPGuino hardware to respond to the interrupt request caused by the VSS pulse; and for MPGuino to execute the ISR for it, and return to the main display routine. If you go faster than 78 MPH at this point, the MPGuino will receive a second pulse as it is trying to process the first pulse, and the MPGuino will simply ignore the second pulse. 385 microseconds corresponds to 2600 Hz, which appears to be the VSS sampling cutoff frequency for the MPGuino.

The addition of a vss debounce of 1 ms is going to trash that VSS pulse length.

You're on the correct path. Putting a divide-by-16 circuit will drop down the VSS pulse frequency to something that MPGuino will handle.

[alexander.foti]

Thanks t-vago

Its nice to know that my random thoughts are backed up by some numbers from inside the mpguino brain.

That circuit I posted, should divide by 16 and give me approximate 7500 pulses per mile!

Not quite sure why my bike has so many pulses per mile.

[P-hack]

sounds like an abs sensor (high resolution). Is there another vss on the bike (how does the speedo work?)

[alexander.foti]

Originally Posted by P-hack

sounds like an abs sensor (high resolution). Is there another vss on the bike (how does the speedo work?)

It's the speed sensor from the gearbox that drives the speedometer that I have tapped into. I avoided the abs sensors on purpose. Honda motorbike vss's are very high resolution. My xl125 had a similar high number but couldn't go past 75, so was never an issue.

[P-hack]

interesting, fyi I don't reach for discrete chips much anymore, since the micro-controllers are so cheap and I have a better chance of debugging them.

There is a standard arduino example in Arduino - ButtonStateChange

remove all the serial crap, modify it to divide by 24 instead of 4, and use the led pin as the output to the mpguino vss input.

If you have an uno, you can use it to program one of these (atmega w/uno bootloader, $1.98):
New ATMEGA328P PU with Arduino Uno Bootloader ATMEL Free Shipping from USA 2014 | eBay

and get the size down to one chip. I don't know much about flip flops, except that they leave me with a soft forehead.

[alexander.foti]

Originally Posted by P-hack

interesting, fyi I don't reach for discrete chips much anymore, since the micro-controllers are so cheap and I have a better chance of debugging them.

There is a standard arduino example in Arduino - ButtonStateChange

remove all the serial crap, modify it to divide by 24 instead of 4, and use the led pin as the output to the mpguino vss input.

If you have an uno, you can use it to program one of these (atmega w/uno bootloader, $1.98):
New ATMEGA328P PU with Arduino Uno Bootloader ATMEL Free Shipping from USA 2014 | eBay

and get the size down to one chip. I don't know much about flip flops, except that they leave me with a soft forehead.

I have zero Arduion experience I think I would have to look at a arduino traning guides or something to get me going, I suppose I could have done that instead.

It costs about the same in parts I suppose.