PICList Project

The Weeder Frequency Counter PIC 16F84 port by Peter Cousens

This is a port by Peter Cousens to the PIC 16F84 of the  50Mhz Frequency counter kit {originally available} from Weeder Technologies . Since it uses a base PIC that is easily programmable, and provides a usefull bit of bench test equipment at very low cost, it makes an ideal PIC learning project. If you don't want to spend the time on the PCB, collecting the parts or even not programming the uP, you can order the kit (for a very resonable price) from http://www.weedtech.com

News: Weeder Tech no longer makes this kit. They have moved on to a very nice version that works with a local PC via the serial port for display and control. It is also "stackable" for multiple counters at once or with other modules for control and measurement of all kinds. See
http://www.weedtech.com for more information. The original kit has been licenced to Invent Electronics and Ken has made some improvements and provides a very nice (closed source) kit for $49 and a PCB for $10 (prices as of 2004/03/05)

The result is a nice frequency counter that reads frequency from 1 Hz to 50 MHz and displays it on a 16 character LCD display. Auto-range feature provides floating decimal point and automatic placement of suffix (Hz, KHz, or MHz). Gate speed automatically decreases to one second below 100 KHz to display frequency with a resolution down to an amazing 1 Hz.

• Auto-ranging with floating decimal point.
• Up to 7 digits displayed.
• Auto-adjusting gate speed (0.1 sec to 1 sec).
• Microcontroller-based circuitry provides for simplicity, ease of assembly, and highly stable readout.
• Sensitivity approximately 100 mV RMS (100 Hz to 2 MHz), 800 mV RMS @ 50 MHz.
• Input overload protected.

You will need:

• The circuit you may want to make a PCB
• The files are as follows (right click and save as .asm or .hex files)
  • wct 5.asm or .hex (right click on hex and select "Save as...") is the original program Peter ported to 16f84 in October 1998
  • wct6.asm is a version that diplays an introductory message. It is not assembled it as you should change it to your own personalised message and options. There is lots of spare program space. DO NOT FORGET TO SET THE WatchDog TIMER TO OFF AND THE OSC TO XT
  • weedfreq8x2LCD is a version for two line, 8 char per line LCD displays
• A way to program the uP. (one of the simplest ways is Tony Nixons ASCII Programmer )

Also:

• LCD Front Panel Set: $8!
  - 2x16 LCD HD44780 controller
  - 4 push buttons - 3 LEDs - 2x12 header

• Other great PICList projects
• Microchip PIC LCD Display IO

See also:

• http://web.archive.org/web/20020114154758/http://www.qsl.net/om3cph/lcd.html Archive version of another, related but simpler design.+
• http://panteltje.com/panteltje/pic/freq_pic/ (cached 2010/04/12) Frequency Counter in a DB9 backshell. Microchip PIC 16F648A program to measure frequency, and display it via the PC RS232 serial port.
• http://freenet-homepage.de/dl4yhf/freq_counter/freq_counter.html Frequency Counter with PIC16F628 and LED 7 Segment display.
• http://www.geocities.com/alibhernlem/Radio/freq.html  Modifications that allow up to 80Mhz. (cached 20060208)
• http://www.weedtech.com Home of the original kit (no longer available)
• http://www.invent-electronics.com New kit
• http://www.sxlist.com/techref/new/letter/news0304.htm 15 MHz PC hosted version with Serial interface and must lower parts count.

Comments:

• spamdigs.dxus at -Remove-gamil.com " no puedo hacer funcionar el contador de frequencias mostrado, hay un error con el LCD, no enciende" +
   
• spamaceware at -Remove-spray.se

• I have found a bug. When the display should show 255Hz, it shows 511Hz. 254 or 256 is fine, but not 255. The same goes for 511. It shows 767 instead.
  767 -> 1023
  1023 -> 1279
  1279 -> 1535
  1535 -> 1791
  1791 -> 2047
  2047 -> 2303
  2303 -> 2559
  2559 -> 2815
  2815 -> 3071
  
  I didn't bother to test more frequencies. I'm not very good at asm so I can't see why this happens. Maybe someone else has the solution. /Daniel

• Bary Smith says: "4 bit LCD / Serial Output Here is my updated version of the driver code for this using the PIC16F628 as a drop in replacement for the F84 (F84 is also still supported). The other main changes are a switch to 4-bit LCD interface to free up some pins and USART output so the frequency can be fed to a PC COM port."
• spamoswa_mene at -Remove-yahoo.com.mx " if you want to measure more than 80mhz with this counter without a prescaler just see
  http://www.geocities.com/alibhernlem/Radio/freq.html Make the modifications shown on the page at that link (cached 20060208) and use a 74AS00,
  I`ve measured no more than 80mhz because that is the highest frequency source I had in hand, I guess it could get higher.
  It is important the AS in the 74AS IC because they work at higher frequency.

  +

• Hi, I just got this circuit to work, ended up using the WCT5.asm file and adding the code for 2x8 then compiling in MPLAB. One thing that really confused me was the schematic provided for this circuit.. you have to notice that the data buss lines get reversed.. IE pin 6 on the PIC goes to pin 7 on the LCD, not pin 14 as it would apear at first glance.. just hoping someone else can avoid this problem. Before when i had the data lines reversed the LCD just displayed the last half as black boxes.. so that is probably the reason that some people were getting the black boxes.+
• spammss001 at -Remove-hotmail.com

  I've made a pcb for this circuit, I omitted the preamp as i'm using it for a homebrew function generator. If anyone wanna use this pcb I'd be happy to email it to you.

  Thanks! I've posted the files here: Frequency Counter PCB
   

• tzhang: some lcd can't init with this program, because the lcd need time
  to process the instruction. so i insert some "call int_del"
  into the start routine. then it works.+
   
• WoW! Thanx for the 8X2 code!i tried making it myself but i failed.I did a search for 16X1 Lcd but could not find it. Now i can have my own frequency counter. The listing that contains a startup message is all messed up,i sorted it out and modified it for the 8X2 LCD, where should i mail it so that it can be added to this webpage?
   
  James Newton replies: Just post it using the form at the bottom, or email it to webmaster. + +

• spamcklymko at -Remove-hotmail.com

  I have a fix for the pesky 8x2 displays that have been packaged as 16x1 displays. If you are only getting the first half of the display to work let me know. I'll send you the code that worked for me. (tested on model L1671 8x2 display)

  Thanks! I've posted the code here: 8x2 LCD code +

• Having tried the vanilla WCT5 to build the frequency ctr, i found that it didn't work. So i added a CONFIG line in the ASM source, and then it worked flawlessly! My CONFIG statement looks like this: __CONFIG _CP_OFF & _XT_OSC & _WDT_OFF & _PWRTE_ON regards, --Thilo

  Thanks much for the help!

Steve Brune says:

If you use the 16F84A for this project the software needs to be updated for bank switching to access the OPTION, TRISA and TRISB registers. The OPTION and TRIS commands compile with a warning in MPIDE but do not execute when burned in the 16F84A microcontroller.

Questions:

• Please post your questions on the questions page (click here). Your question may already be answered there!

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