As said in a different topic I wanted to experiment with frequency sensing of a FAN pwm signal comming from a motherboard (input capture) on a Xmega.
At the moment I am doing so and I am running against some problems which I cannot figure out by myself.
As a start I used 2 sources of information:
https://www.avrfreaks.net/comment...
and
http://www.dolman-wim.nl/xmega/b... (paragraph 23.18)
And of course the information from the specific FAN:
http://media.digikey.com/pdf/Dat...
Furthermore I created a PWM LED which I could run at 0,5Hz (to test with variable PW).
My problem is that when I run the PWM led with 0,5Hz and lets say 80% this is detected and shown in my USART output. Same for 24k Hz and 80%.
I then get:
Current Frequency: 24060.1503 Hz Current PulseWidth: 80 % Current Frequency: 24060.1503 Hz Current PulseWidth: 80 % Current Frequency: 24060.1503 Hz
The code to generate the PWM:
#define Freq_Val 24000.0F // Required frequency #define PW_Val 80 // Pulse Width (percent) #define ICPreScale 1 // Input Capture Pre-scaler 1/2/4/8/64/256/1024 #define OCPreScale 1 // Output Control Pre-scaler 1/2/4/8/64/256/1024 uint32_t period; // Changed to 32-bits uint32_t pulseWidth; // Changed to 32-bits uint16_t FreqVal; uint16_t PWVal; float frequency;
void init_pwm(void)
{
PORTD.DIRSET = PIN0_bm;
TCD0.CTRLB = TC0_CCAEN_bm | TC_WGMODE_SINGLESLOPE_gc;
switch ( OCPreScale ) {
case 1:
TCD0.CTRLA = TC_CLKSEL_DIV1_gc;
break;
case 2:
TCD0.CTRLA = TC_CLKSEL_DIV2_gc;
break;
case 4:
TCD0.CTRLA = TC_CLKSEL_DIV4_gc;
break;
case 8:
TCD0.CTRLA = TC_CLKSEL_DIV8_gc;
break;
case 64:
TCD0.CTRLA = TC_CLKSEL_DIV64_gc;
break;
case 256:
TCD0.CTRLA = TC_CLKSEL_DIV256_gc;
break;
case 1024:
TCD0.CTRLA = TC_CLKSEL_DIV1024_gc;
break;
}
FreqVal = (F_CPU/(Freq_Val*OCPreScale))-1; // Page 173 Xmega AU manual
PWVal = ((PW_Val*(uint32_t)FreqVal)/100);
TCD0.PER = FreqVal;
TCD0.CCA = PWVal;
}
Then my code to init the freq and PW:
void init_inputFREQcapture(void)
{
PORTD.DIRCLR = PIN4_bm;
PORTD.PIN4CTRL = PORT_OPC_PULLDOWN_gc | PORT_ISC_RISING_gc;
EVSYS.CH0MUX = EVSYS_CHMUX_PORTD_PIN4_gc;
EVSYS.CH0CTRL = EVSYS_DIGFILT_8SAMPLES_gc;
TCC0.CTRLD = TC_EVACT_FRQ_gc | TC_EVSEL_CH0_gc;
TCC0.CTRLB = TC0_CCAEN_bm | TC_WGMODE_NORMAL_gc;
switch ( ICPreScale ) {
case 1:
TCC0.CTRLA = TC_CLKSEL_DIV1_gc;
break;
case 2:
TCC0.CTRLA = TC_CLKSEL_DIV2_gc;
break;
case 4:
TCC0.CTRLA = TC_CLKSEL_DIV4_gc;
break;
case 8:
TCC0.CTRLA = TC_CLKSEL_DIV8_gc;
break;
case 64:
TCC0.CTRLA = TC_CLKSEL_DIV64_gc;
break;
case 256:
TCC0.CTRLA = TC_CLKSEL_DIV256_gc;
break;
case 1024:
TCC0.CTRLA = TC_CLKSEL_DIV1024_gc;
break;
}
}
void init_inputPWcapture(void)
{
PORTD.DIRCLR = PIN5_bm;
PORTD.PIN4CTRL = PORT_OPC_PULLDOWN_gc | PORT_ISC_RISING_gc;
EVSYS.CH1MUX = EVSYS_CHMUX_PORTD_PIN5_gc;
EVSYS.CH1CTRL = EVSYS_DIGFILT_8SAMPLES_gc;
TCC1.CTRLD = TC_EVACT_PW_gc | TC_EVSEL_CH1_gc;
TCC1.CTRLB = TC1_CCAEN_bm | TC_WGMODE_NORMAL_gc;
switch ( ICPreScale ) {
case 1:
TCC1.CTRLA = TC_CLKSEL_DIV1_gc;
break;
case 2:
TCC1.CTRLA = TC_CLKSEL_DIV2_gc;
break;
case 4:
TCC1.CTRLA = TC_CLKSEL_DIV4_gc;
break;
case 8:
TCC1.CTRLA = TC_CLKSEL_DIV8_gc;
break;
case 64:
TCC1.CTRLA = TC_CLKSEL_DIV64_gc;
break;
case 256:
TCC1.CTRLA = TC_CLKSEL_DIV256_gc;
break;
case 1024:
TCC1.CTRLA = TC_CLKSEL_DIV1024_gc;
break;
}
}And in my main loop:
while(1)
{
// Current period & pulse width
period = TCC0.CCA;
pulseWidth = TCC1.CCA;
// Calculate
frequency = (F_CPU/((float)period*ICPreScale));
// Frequency from last capture.
uint16_t d1 = frequency; // Get the integer part (678).
float f2 = frequency - d1; // Get fractional part (678.0123 - 678 = 0.0123).
int d2 = trunc(f2 * 10000); // Turn into integer (123).
sprintf (str, "%d.%04d", d1, d2);
//sprintf(str,"%u", frequency);
dbgPutStr("Current Frequency: ");
dbgPutStr(str);
dbgPutStr(" Hz\r\n");
// PulseWidth from last capture.
sprintf(str,"%lu", (((pulseWidth+1)*100)/period));
dbgPutStr("Current PulseWidth: ");
dbgPutStr(str);
dbgPutStr(" %\r\n");
_delay_ms( BLINK_DELAY_MS ) ; // wait.
}The result when I am trying to get the frequency from my FAN PWM:
Current Frequency: 1252.4461 Hz Current PulseWidth: 4 % Current Frequency: 1204.1845 Hz Current PulseWidth: 4 % Current Frequency: 1203.1884 Hz Current PulseWidth: 4 % Current Frequency: 1250.7817 Hz Current PulseWidth: 4 % Current Frequency: 1244.3614 Hz Current PulseWidth: 4 % Current Frequency: 1990.7926 Hz
These are with the same settings as blinking the led...
I have read the manual multiple times, but it might be something with the PWM signal type. But at the moment I am shooting blind. Hope someone can give me a tip what to look for.
Thank you all in advance.
