Trying to measure TACH pulses.

[eagleman]

I'm using a PIC18F67K40 on PBP gold at 64Mhz and I am trying to measure "TACH" pulses on PORTB.0 that are being simulated from a signal generator. I'm trying three different methods just to see how things work. I am thinking that once I can be assured that the pulses are being recognized by PORTB.0 in any form or fashion then I can proceed with actual circuitry work out my permanent code to recognize and report true RPM. Problem is that I can't seem to get PORTB.0 (or PORTB.1, etc..) to recognize the signal from the signal generator.
Currently using 60-200 Hz at 5 volts from the signal generator in square wave ( with varying duty cycles, but I've tried sine, sawtooth, and various pulses types).

My test code is basically:

Do_Tach:
COUNT PORTB.0, 1000, RPM ' to count number of pulses in 1 second and store in word RPM
RPM = RPM * 60
serout LCD_out,6,[017,0,0," RPM: ", #RPM," "] ' print out to my LCD on line 0.
return
Do_Count:
COUNT PORTB.0, 1000, PCount' to count number of pulses in 1 second and store in word PCount
serout LCD_out,6,[017,0,1,"COUNT: ",#PCount, "cnts/sec "] ' print out on my LCD line 1
return
Do_Pulse:
PULSEIN PORTB.0, 1, TPulse ' read pulse on PORTB.0 and store result in word TPulse.
serout LCD_out,6,[017,0,2,"PULSE TIME: "] ' print out on my LCD line 2
return

Thus runs as a loop with a loop counter and the loop count is displayed on my LCD line 3 (code not shown)

I can see the generated signals at my board with my scope.
I can see the loops being counted on my LCD.
I get no response from PORTB.0 or PORTB.1

Before I build a new board I thought it would be best to check with the forum to see if I have missed something, done something stupid or whatever. I have not tried interrupts on this but can see where it might be needed for the PULSEIN statement.
I thought about doing an interrupt on a PORTB.0 change to read the system clock and compare it to the last interrupt time, but can't remember how to read the clock.

Open to any criticism that would help.

[Ioannis]

Maybe Timer module can help you on this?

The Tachometer pulses will be counted by a timer and the timer will be gated by a controlled time base.

This is the base of a frequency counter. And you can do other things while the timer counts pulses instead of waiting as is the case with COUNT command.

Ioannis

[HenrikOlsson]

What about the good old analog stuff?

ANSELB.0 = 0   ' Enable digital input circuitry to work properly on PortB,0

[Ioannis]

Maybe I do not see your point Henrik. How does this help?

Ioannis

[Dave]

Ioannis, The porta and portb default to digital input buffers DISABLED. They need to be set for digital operation before this type of use. Also I have to ask, Why are you counting pulses to get the RPM value? Seems like kind of a crude method. I would look at the time between leading edges and then compute the RPM value. Much faster...

[Ioannis]

Oh I see. I thought that was trivial and eagleman would have correct setup of PIC.

Ioannis