Posted on March 27, 2014 at 18:04I am timing the ADC conversion from TRGO to EOC. I calculate that the conversion should take 3.5us but I measure a minimum of 4.0us using an oscilloscope.
I have included the relevant code loop below.
Please does anyone know where the extra time is coming from?
My application requires close coordination of the ADC with external signals.
//////////////////////////////////////////////////////////
TRGO = TIM1 CH4 = (counter=0x01)
ADC clk = 4MHz
conversion = 14 clocks / 4Mhz = 3.5us
measured: 4.0us (minimum) between toggles
////////////////////////////////////////////////
while(!(GPIOC->IDR & 0x08)){} // wait for pwm sig high (counter=x)
for (tempi=0; tempi<5000;tempi++)
{
while(GPIOC->IDR & 0x08){} // wait for pwm sig low (counter=0)
GPIOB->ODR ^= 0x80; // toggle pin
ADC1->CSR = 0x00;
/
/ clr EOC (@ top of loop to catch 1st pass)
while(!(ADC1->CSR & 0x80)) {} // wait for ADC completion
GPIOB->ODR ^= 0x80; // toggle pin
while(!(GPIOC->IDR & 0x08)){} // wait for pwm sig high (cntr=x)
}
