Freq.Synth for a specific amount of ms or us

Jkane · 2014-04-23 10:57

Hello,

I'm new to this, but I'm trying to use Freq.Synth to run for a specific amount of time. I have a logic analyzer attached to validate the length and frequency, the frequency is usually perfect, but I can't seem to get the duration correct, I've tried it many different ways, but nothing gives me expected or predictable results. I know this is simple code but it shows what I have tried.

_clkmode = xtal1 + pll16x
_xinfreq = 5_000_000

Pin1 = 0
Frequency1 = 30_000_000

Freq.Synth("A",Pin1, Frequency1)
waitcnt(clkfreq/1000+cnt) 'wait for 1 millisecond
Freq.Synth("A",Pin1, 0)

Freq.Synth("A",Pin1, Frequency1)
waitcnt(clkfreq/10000+cnt) 'wait for 1 microsecond
Freq.Synth("A",Pin1, 0)

I have also tried

ms := cnt + (1 *(clkfreq/1_000)) ' 1 millisecond
repeat until (cnt >= ms)
Freq.Synth("A",Pin1, Frequency1) 'Synth({Counter"A" or Counter"B"},Pin, Freq)

I do get times, but they make little sense.

I also noticed that cnt shows a negative number, which seems strange

Cnt counter is: 1588437453
ms delta is: 1588716333
Clkfreq counter is: 80000000
===========================================

Cnt counter is: -693574839
ms delta is: -693298423
Clkfreq counter is: 80000000

anyway, Freq.Synth does exactly what i want, but I just need an accurate way to set duration.

Thanks

Jeff
===========================================

JonnyMac · 2014-04-23 11:30

Since that object uses a counter in the current cog, all you have to do is clear the counter. Be careful of minimum delays -- you can't do a 1 microsecond delay in Spin.

This blob of code should output your frequency for ~10ms, then turn it off for ~90ms

repeat
    freq.synth("A", P1, FREQ1) 
    waitcnt(cnt + (clkfreq / 100))
    ctra := 0
    outa[P1] := 0
    waitcnt(cnt + (9 * clkfreq / 100))

BTW, this is a method I have in my standard programming template that does what you want (kill the output with frequncy input of 0). It doesn't work for all ranges of the counter, though.

pub set_freq(ctrx, px, fx)

'' Sets ctrx to frequency fx on pin px (NCO/SE mode)
'' -- fx in hz
'' -- use fx of 0 to stop counter that is running

  if (fx > 0)                             
    fx := ($8000_0000 / (clkfreq / fx)) << 1            ' convert freq for NCO mode    
    case ctrx
      "a", "A":
        ctra := ((%00100) << 26) | px                   ' configure ctra for NCO on pin
        frqa := fx                                      ' set frequency
        dira[px] := 1                                   ' make pin an output
     
      "b", "B":                         
        ctrb := ((%00100) << 26) | px  
        frqb := fx                    
        dira[px] := 1

  else
    case ctrx
      "a", "A":
        ctra := 0                                       ' disable counter
        outa[px] := 0                                   ' clear pin/driver 
        dira[px] := 0                                  
     
      "b", "B":                         
        ctrb := 0 
        outa[px] := 0  
        dira[px] := 0

Jkane · 2014-04-23 19:22

Thank you, it works very well, as you mentioned in your reply ~ms, I'll work with it tomorrow but you wouldn't have an assembler /machine language version would you? for this project things run at about 40-20 Mhz, about 12 pins, so I think things will be fine, worst case I'll use an external crystal for the system clock (hardcoded) then I won't have to tie up cog's with housekeeping. 8 lines are for variable data,but actually 4 are just mirrors (inverted). I think this project is going to end up with a basic stamp, (switches, sensors, lcd's and led's) <=> prop board (main device interface) <=> prop demo or raspberry pi (HCI stuff).

regards

Jeff

JonnyMac · 2014-04-23 23:32

I'm not sure what you mean "about 12 pins". Are you wanting 12 oscillating pins?

Jkane · 2014-04-24 05:30

Sorry,

Perhaps a better explaination, I'm interfacing to a printer head, the IO lines are

1 - 40Mhz clock (Oscillator MAX045, always on)
2 - 30Mhz clock (Oscillator MAX045T with enable/disable pin)
3 - data line 1 30Mhz (variable bits from a bit-buffer about 640 bits long)
4 - data line 2 30Mhz same as above item 3
5 - data line 3 30Mhz same as above item 3
6 - data line 4 30Mhz same as above item 3
7 - dataline 5,6,7,8 inverser of dataline 1-4
8 - termination data signal 1 1us
9 - termination data signal 2 1 us signal 8 and 9 are on different pins

and two serial lines tx and rx (cmd data to head - from bit buffer)

so the things that change are 3-7 and 1,2,8 and 9 can be hardcoded as long as i can turn them off and on when required.

The propeller will be responsible for running the head, the BS2 will run all the diagnostic switches and sensors (flowmeters, current, pressure and LCD displays, so I'll connect the BS2 and the Propeller together

and then the prop demo or rasberry pi will be the HCI (Human Computer Interface) - keyboard, mice, display) (which I think will be connected to both the prop and the BS2

anyway, currently I am just working on the Prop to head, the code you gave me works, I was just curious what that code would look like in prop assembler.

regards

Jeff

Tracy Allen · 2014-04-24 10:38

I made an OBEX entry, ncoBurst.spin, where you choose both the output frequency and the number of pulses. Number of pulses is of course directly related to the burst duration.

PUB GenStart(pin, Fx, Nx) | fa, pb

It uses two counters to accomplish that, and it is accurate even up to the maximum frequency and short duration. The counter output could be made differential so that you get both the true and inverted outputs.

I don't understand how this print head works, to need such high frequencies on multiple lines.

Freq.Synth for a specific amount of ms or us

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