Spin help

Cenlasoft

Hello,
I am trying to send a squarewave on two pins that are 180 degrees apart. I got that done I think. I am using an h-bridge to excite an ultrasonic transducer. from 5 V I will come out with a 10 vpp. It works. My spin code has something wrong. On the scope I see a squarewave (40KHZ). How do I time it to get .5 ms of the 40khz pulse then turnoff the h-bridge and listen for an echo.
Thanks, Cenlasoft

{{
  Template.spin
  Curtis Desselles
}}
Con

 _clkmode = xtal1 + pll16x
 _xinfreq = 5_000_000

 Pin1   = 0
 Pin2   = 1
 
  
  
Var


Obj
Pub Main
repeat
  TX_Out                          'TX a pulse x 5
  dira[Pin1..Pin2]~~              'Make pins output
  outa[Pin1..Pin2] := %00         'Turn off h-bridge

Pub TX_Out | i
repeat i from 0 to 4
  ctra := %00101 <<26 + Pin2<<9 +Pin1
  frqa := 1<<31 / (clkfreq / 80_000)
  dira |= |<Pin1 + |<Pin2
Return  

Mike Green

1) Note that in Main, the DIRA bits for pins 1 and 2 are already set to output mode. You don't have to do it again.

2) If you still want pins 1 and 2 to be outputs with the h-bridge off, you could zero CTRA and do: OUTA[Pin1..Pin2]~ or OUTA[Pin1..Pin2] := $00

3) To get a particular pulse length, just wait that time, then set CTRA and the output pins to zero. Use: WAITCNT(CLKFREQ/2000 + CNT)

4) Remember that other statements will take a few microseconds. That may affect the 0.5ms pulse length. You may have to shorten the delay to compensate.

The code brackets use [] not <>

Ariba

The simplest way is to set the pins high in outa to stop the 40kHz output. This works because outa and the counter output are ORed together:

_clkmode = xtal1 + pll16x
 _xinfreq = 5_000_000

 Pin1   = 0
 Pin2   = 1

Pub Main
  ctra := %00101 <<26 + Pin2<<9 +Pin1
  frqa := 1<<31 / (clkfreq / 80_000)
  dira[Pin1..Pin2] := %11

  repeat
    outa[Pin1..Pin2] := %00       'on
    waitcnt(clkfreq/2000 + cnt)   'wait 0.5ms
    outa[Pin1..Pin2] := %11       'off
    ' wait for response here
    waitcnt(clkfreq/2 + cnt)      'pause 0.5s (optional)

Andy

Mark_T

Ariba wrote: »

The simplest way is to set the pins high in outa to stop the 40kHz output. This works because outa and the counter output are ORed together:


Andy

Depending on how the pins control the H-bridge setting them both high may short it out. We know from the original code that 00 turns it off.

Cenlasoft

Thanks everyone. Mark_T got it right. Setting both pins high on the h-bridge burned it. No problem though, I have plenty of them. I learned something. Thanks Ariba, good code to use. I'll play with the new setup and post the results. Thanks Mike for the suggestions, they helped.
Cenlasoft.

Ariba

You can also switch on and off with dira[Pin0..Pin1] an use two pulldown resistors for the off state.
dira[Pin0..Pin1] := %11 'ON
dira[Pin0..Pin1] := %00 'OFF

Andy

Mickster

Hello, Curtis. I sent you a PM.

Regards,

Mickster