periodic wave

[Olaf Petzold <opetzold@wit.regiocom.net>]

Hallo,

please help to find a solution - I didn't find it yet. I have a task with the
period_ns/f_rt and want to get out a rectangle wave with a frequency f_wave.
Using the rtfs I set period_ns und f_wave. The problem is the non-linear
dependence between f = 1/T. The frequency of the wave I pretend linear but the
result isn't it by this peace of code:

rtf_handler:
		/* period_ns for the task is eq. to 1kHz */
		waveform_freq = (unsigned int)rtf_msg.data2;	/* Hz */
		waveform_ticks = (unsigned int)(1/((double)waveform_freq)*1e3);

thread_code:

      if(square_on) {
	  ao_data[AO_CURR1_CH] = ao_data_wavegen[AO_CURR1_CH];
	  ao_data[AO_CURR2_CH] = ao_data_wavegen[AO_CURR2_CH];
	  
	  if( !(loop_index % waveform_ticks) )
	      square_on = 0;		/* turn off */

      } else { /* !square_on */
	  ao_data[AO_CURR1_CH] = (sampl_t)NI_PCI_MIO_XE10_MAXDATA - ao_data_wavegen[AO_CURR1_CH];
	  ao_data[AO_CURR2_CH] = (sampl_t)NI_PCI_MIO_XE10_MAXDATA - ao_data_wavegen[AO_CURR2_CH];
	  
	  if( !(loop_index % waveform_ticks) )
	      square_on = 1;		/* turn on */

      }

The question is, how can calculate the waveform_ticks in that way, that the
output is proportional to the given waveform frequency regards to the realtime
module frequency?

Thanks	Olaf