Post by thread:Frequency generator?

Hi everyone, I'm trying to find some code for a frequency genetator using a PIC. 0Hz to 10khz 0.5Hz or 1Hz increments. I have been experiementing with PIC16C84, dividing a known frequency from the TRM0 Interupt, but dividing freqencies will not give me the freqency increments I need. eg 1MHz/100 = 10kHz 1MHz/101 = 9900.9Hz 1MHz/1,000,000 = 1Hz 1MHz/1,000,001 =0.9999999 Any help will be greatly appretiated Max ----------------------- Max Prager <spam_OUTmpragerTakeThisOuTcyllene.uwa.edu.au> ---------------------

Hi, > Hi everyone, > I'm trying to find some code for a frequency genetator using a PIC. > 0Hz to 10khz 0.5Hz or 1Hz increments. > I have been experiementing with PIC16C84, dividing a known frequency > from the TRM0 Interupt, but dividing freqencies will not give me the > freqency increments I need. > eg 1MHz/100 = 10kHz > 1MHz/101 = 9900.9Hz > > 1MHz/1,000,000 = 1Hz > 1MHz/1,000,001 =0.9999999 > > Any help will be greatly appretiated > I designed a 1-10KHz frequency generator with a 1Hz resolution about a year ago. I used a numerically controlled oscillator (NCO) IC from Harris (HSP45102) with a PIC. You simply download the divisor to the IC via its SPI interface. It actually outputs a 12 bit sine wave but I only used the most significant bit to get a square wave. I don't think that a PIC alone would be sufficient. You could also use a PLL frequency synthesizer. The problem is that 1Hz-10KHz spans 4 decades which would make the oscillator design tricky. Niki

At 02:44 16.7.1998 -0400, you wrote: >Hi everyone, > I'm trying to find some code for a frequency genetator using a PIC. >0Hz to 10khz 0.5Hz or 1Hz increments. >I have been experiementing with PIC16C84, dividing a known frequency >from the TRM0 Interupt, but dividing freqencies will not give me the >freqency increments I need. >eg 1MHz/100 = 10kHz > 1MHz/101 = 9900.9Hz > > 1MHz/1,000,000 = 1Hz > 1MHz/1,000,001 =0.9999999 > >Any help will be greatly appretiated Hello, in the past, I designed the freq. generator (PIC driven) with DDS (Direct Digital Synthesis) IC. Of course, it was for frequencies around 100 Mhz, but I think that you can use similar approach. The IC I used was AD9850 (from Analog Devices) which work up to 180 Mhz (or similar) with resolution 0.029 Hz. Also, if I remember correctly, there is a design of digitally controlled freq. generator in Maxim datasheet for MAX038 function generator IC. The resolution is 1 Hz, but I am not sure and I don't have the datasheet handy here. Check their web site http://www.maxim-ic.com Best regards PavelK ************************************************************************** * Pavel Korensky * * DATOR3 LAN Services spol. s r.o. * * Modranska 1895/17, 143 00, Prague 4, Czech Republic * * * * PGP Key fingerprint: F3 E1 AE BC 34 18 CB A6 CC D0 DA 9E 79 03 41 D4 * * * * SUMMA SCIENTIA - NIHIL SCIRE * **************************************************************************

At 09:58 AM 7/16/98 GMT+0200, you wrote: {Quote hidden}>Hi, > >> Hi everyone, >> I'm trying to find some code for a frequency genetator using a PIC. >> 0Hz to 10khz 0.5Hz or 1Hz increments. >> I have been experiementing with PIC16C84, dividing a known frequency >> from the TRM0 Interupt, but dividing freqencies will not give me the >> freqency increments I need. >> eg 1MHz/100 = 10kHz >> 1MHz/101 = 9900.9Hz >> >> 1MHz/1,000,000 = 1Hz >> 1MHz/1,000,001 =0.9999999 >> >> Any help will be greatly appretiated >> >I designed a 1-10KHz frequency generator with a 1Hz resolution about a >year ago. I used a numerically controlled oscillator (NCO) IC from >Harris (HSP45102) with a PIC. You simply download the divisor to the IC >via its SPI interface. It actually outputs a 12 bit sine wave but I only >used the most significant bit to get a square wave. > >I don't think that a PIC alone would be sufficient. You could also use a >PLL frequency synthesizer. The problem is that 1Hz-10KHz spans 4 decades >which would make the oscillator design tricky. > Motorola MC145162 is also a good choise for frequency division, you may use this IC to output to two different frequencies. More DDS chip from Analog Device may be used, or use PIC to do the DDS, I've read a article from Motorola web talking about DDS using a MC68HC05 I believe.