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Prop friendly frequency IC chip?? — Parallax Forums

Prop friendly frequency IC chip??

w4fejw4fej Posts: 264
edited 2014-10-06 08:00 in Propeller 1
Does anyone know of a SMALL IC chip frequency counter that is:

A: Prop friendly using I2C, SPI or TTL level RS-232 serial communications
B: Counts 3.0 Mhz to 30 Mhz to a resolution of 1 Khz (Extreme accuracy not required)
C: operates on 3.3 vdc, 5.0 vdc or 12 vdc.
D: Preferably standard pin spacing to fit on a Prop proto board (.1" spacing)
E: Does not need to drive a display at all as that is already in place. (The display that is)
F: Cheap!

This counter won't be used as "test equipment" but rather an indicator of a low power HF carrier frequency. (Free air sampling, no direct connection to transmitter)

Is the Prop itself capable of doing the job by sampling the carrier (separate cog) and turning it into square waves to measure the time between the pulses or some other method??

Thanks for reading..

Comments

  • kwinnkwinn Posts: 8,697
    edited 2014-10-04 11:23
    The propeller counters can do that easily, although you may need to use a comparator or opamp to amplify and convert the signal to a square wave.

    What is the amplitude of the incoming signal?
  • jmgjmg Posts: 15,173
    edited 2014-10-04 15:47
    w4fej wrote: »
    Does anyone know of a SMALL IC chip frequency counter that is:

    A: Prop friendly using I2C, SPI or TTL level RS-232 serial communications
    B: Counts 3.0 Mhz to 30 Mhz to a resolution of 1 Khz (Extreme accuracy not required)
    C: operates on 3.3 vdc, 5.0 vdc or 12 vdc.
    D: Preferably standard pin spacing to fit on a Prop proto board (.1" spacing)
    E: Does not need to drive a display at all as that is already in place. (The display that is)
    F: Cheap!

    This counter won't be used as "test equipment" but rather an indicator of a low power HF carrier frequency. (Free air sampling, no direct connection to transmitter)

    Is the Prop itself capable of doing the job by sampling the carrier (separate cog) and turning it into square waves to measure the time between the pulses or some other method??

    Thanks for reading..

    The Prop can measure Frequency, if you scale to the right places.
    Look at the XX4060 series, for very cheap, ev 74LVC4060, and they have a small pre-amp.

    Addit : If you want small, then a 74xx2G80 comes in 8 pin SMD, and it can divide by 4, which will give 1KHz resolution in 4ms measure time, and a fMax of well over 100MHz (but no preamp - add a 2GU04 for that)
  • AribaAriba Posts: 2,690
    edited 2014-10-04 20:40
    w4fej wrote: »
    ...
    Is the Prop itself capable of doing the job by sampling the carrier (separate cog) and turning it into square waves to measure the time between the pulses or some other method??

    Thanks for reading..

    The Propeller counters can measure frequencies up to 30 MHz if the Propeller is clocked with 80 MHz. Just use a counter in POSEGE mode and count the pulses for one second. This can even be done in Spin: 
    CON
  _clkmode  = xtal1 + pll16x
  _xinfreq  = 5_000_000

  INPIN = 7
  
OBJ
  term :  "FullDuplexSerial"
      
PUB Main | time, Hz
  term.start(31,30,0,115200)
  ctra := %01010<<26 + INPIN    'PosEdge mode
  frqa := 1                      
  time := cnt
  repeat
    time += clkfreq
    waitcnt(time)
    Hz := phsa
    phsa := 0
    term.dec(Hz)
    term.tx(13)
    This code should send the frequency every second to the Terminal. Set the right pin in the CON section and make sure that your frequency signal at the pin is a logic level signal with max 3.3 Volts. If it is higher use an appropriate resistor.

    Andy
  • jmgjmg Posts: 15,173
    edited 2014-10-04 21:32
    Ariba wrote: »
    ... and make sure that your frequency signal at the pin is a logic level signal with max 3.3 Volts. If it is higher use an appropriate resistor.

    It also needs to be very close to 50% duty cycle.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2014-10-05 00:12
    jmg wrote: »
    It also needs to be very close to 50% duty cycle.

    A flip-flop as a divide by 2 will do that nicely and extends the frequency range to boot.
  • jmgjmg Posts: 15,173
    edited 2014-10-05 02:22
    Peter Jakacki wrote: »
    A flip-flop as a divide by 2 will do that nicely and extends the frequency range to boot.

    Yup, like the 74xx2G80 I suggested in #3 ;)
  • w4fejw4fej Posts: 264
    edited 2014-10-05 06:43
    Thanks to everyone that responded, indeed a lot of good info for me to wade through. I just downloaded and printed out app note AN001 on counters

    There is a gent (ham radio operator, W8ZR) that built an antenna tuner around a Basic Stamp SX (Google E-Z Tuner website) and he has a circuit to pick off the RF to measure the frequency. I'll mock up that circuit and see what we have for levels and shape. He divided the freq down as I guess the SX chip can't directly handle the 30 Mhz end of the range..

    I'm off to do some reading about counters and how they saved civilization...

    Thank you all... Mike B.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2014-10-06 08:00
    jmg wrote: »
    Yup, like the 74xx2G80 I suggested in #3 ;)

    Yep, I missed that but you are always spot on with your suggestions :)
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