LPC2368 low speed adc

lpcware — Wed, 15 Jun 2016 19:49:55 GMT

Content originally posted in LPCWare by kookooli on Sun Jul 13 23:09:19 MST 2014
Hi friends,
I have a problem and i was woundering if someone can help me ...
i want to make samples from a signal via 2368 adc.
Here is my code :

while(j<6000){
buf3[j]=read_adc();
j++;
}

and this is my adc function :
//////////////////////////////////////// READ ADC
unsigned short read_adc(void){
AD0CR&=0xFFFFFF00;
AD0CR|=(1<<24)|(1<<4)|(1<<16); // START=0x01 // BURST=0x01 //
while((AD0DR4&0x80000000)==0);
AD0CR&=0xF8FFFFFF;
return((AD0DR4>>6)&0x03FF);
}
/////////////////////////////////// End of ADC

my problem is here : according to 2368 datasheet every sampling process should last at least 2.44us that means 400ksps
but when i measure conversion time via one of timers , my adc sampling time is about 5.22us that means 191ksps and i dont know why i cant reach 400ksps speed ?????
my cpu clock is 72MHz
adc clock is 72/4=18
my timer clock is 72/4=18
clkdiv is 3 cuz (18)/(3+1)=4.5 and every sampling process should last 11 clock of 4.5 MHz but but mine last 23 clock of 4.5MHz
Please HELP ME

LPC MicrocontrollersのトピックLPC2368 low speed adc

LPC2368 low speed adc