Rob Toulson / Mbed 2 deprecated PE_14-06_ADCConversionTime

by Rob Toulson and Tim Wilmshurst from textbook "Fast and Effective Embedded Systems Design: Applying the ARM mbed"

Dependencies:   mbed

main.cpp@0:c0fbef1ae93c, 2013-06-16 (annotated)

Committer:
robt
Date:
Sun Jun 16 15:42:27 2013 +0000
Revision:
0:c0fbef1ae93c
by Rob Toulson and Tim Wilmshurst from textbook "Fast and Effective Embedded Systems Design: Applying the ARM mbed"

Who changed what in which revision?

UserRevisionLine numberNew contents of line
robt 0:c0fbef1ae93c 1 /* Program Example 14.6: Explore ADC conversion times, programming control registers directly. ADC value is transferred to DAC, while an output pin is strobed to indicate conversion duration. Observe on oscilloscope
robt 0:c0fbef1ae93c 2 */
robt 0:c0fbef1ae93c 3 //….
robt 0:c0fbef1ae93c 4 //….
robt 0:c0fbef1ae93c 5
robt 0:c0fbef1ae93c 6 int main() {
robt 0:c0fbef1ae93c 7 FIO2DIR0=0xFF; // set lower bits port 2 to output
robt 0:c0fbef1ae93c 8 PINSEL1=0x00210000; //set bits 21-20 to 10 for analog output (mbed p18)
robt 0:c0fbef1ae93c 9 //and bits 17-16 to 01 to enable ADC channel 1 (AD0.1, mbed pin 16)
robt 0:c0fbef1ae93c 10
robt 0:c0fbef1ae93c 11 //initialise the ADC.
robt 0:c0fbef1ae93c 12 //….
robt 0:c0fbef1ae93c 13 //….
robt 0:c0fbef1ae93c 14 while(1){ // infinite loop
robt 0:c0fbef1ae93c 15 // start A/D conversion by modifying bits in the AD0CR register
robt 0:c0fbef1ae93c 16 AD0CR &= (AD0CR & 0xFFFFFF00);
robt 0:c0fbef1ae93c 17 FIO2PIN0 |= 0x01; // OR bit 0 with 1 to set pin high
robt 0:c0fbef1ae93c 18 AD0CR |= (1 << ADC_channel) | (1 << 24);
robt 0:c0fbef1ae93c 19 // wait for it to finish by polling the ADC DONE bit
robt 0:c0fbef1ae93c 20 while((AD0GDR & 0x80000000) == 0) {
robt 0:c0fbef1ae93c 21 }
robt 0:c0fbef1ae93c 22 FIO2PIN0 &= ~0x01; // AND bit 0 with 0 to set pin low
robt 0:c0fbef1ae93c 23
robt 0:c0fbef1ae93c 24 ADCdata = AD0GDR; // get the data from AD0GDR
robt 0:c0fbef1ae93c 25 AD0CR &= 0xF8FFFFFF; //stop ADC by setting START bits to zero
robt 0:c0fbef1ae93c 26
robt 0:c0fbef1ae93c 27 // shift data 4 bits to right justify, and 2 more to give 10-bit ADC value
robt 0:c0fbef1ae93c 28 ADCdata=(ADCdata>>6)&0x03FF; //and mask
robt 0:c0fbef1ae93c 29 DACR=(ADCdata<<6); //could be merged with previous line,
robt 0:c0fbef1ae93c 30 // but separated for clarity
robt 0:c0fbef1ae93c 31 //delay(); //insert delay if wished
robt 0:c0fbef1ae93c 32 }
robt 0:c0fbef1ae93c 33 }
robt 0:c0fbef1ae93c 34