1. Analog-to-Digital Converter (ADC)
1/20/2017
Richard Kuo
Assistant Professor

2. Outline 6.0 NuMicro_ADC.ppt Analog-to-Digital Converter Introduction
Lab. ADC Single_Cycle mode (ADC)
Lab. ADC Continuous mode (ADC_4ch)
Lab. To read Variable Resistor (ADC_VR1)
Lab. To read Photoresistor (ADC_Photoresistor)
Lab. To read Thermistor (ADC_Thermistor)
Lab. To read Joystick (ADC_Joystick)
Lab. ADC Triggered by PWM (ADC_Trigger)

3. Signal Conversion
ADC
DAC
Filter

4. Analog to Digital Conversion

5. Digital Conversion Vin is input voltage for ADC to sample
Vref is reference voltage for ADC to compare with Vin
Vref is connected to 3.3V on NUC140 learning board
12-bit ADC : output is a 12-bit binary code, so its value = 0 ~ 4095
Decimal
Binary
Voltage (Vref=3.3V)
0000_0000_0000
0/4096 * 3.3V 1
0000_0000_0001
1/4096 * 3.3V
2048
1000_0000_0000
2048/4096 * 3.3V
4095
1111_1111_1111
4095/4096 * 3.3V

6. ADC Architectures Direct-Conversion ADC
SAR (Successive Approximation Register) ADC
ΔΣ (Sigma-Delta) ADC
Sigma-Delta ADC
SAR ADC
Successive Approximation Register
Direct-Conversion ADC

7. SAR (Successive Approximation Register) ADC
End-Of-Conversion
clock
N-bit
DAC
Vref
Comparator - +
Sample
& Hold
Vin

8. ADC specification 12-bit SAR ADC (10-bit accuracy)
Analog input voltage range: 0~Vref (Max to 5.0V).
Operation voltage: AVDD=3.0V~5.5V;
Input channel:
Up to 8 single-end analog input channels
4 pairs of differential analog input channel.
NUC140 = Up to 800KSPS, NANO102 up to 1MSPS
The maximum ADC operating frequency is 16M Hz
Three ADC operation modes
Single mode
Single-cycle mode
Continuous mode

9. ADC pins configuration
The ADC input pins share with GPIO group A
The ADC input pins must be configured in input type
Single-end input mode
ADC0 ~ ADC7 = PA0~PA7
Differential input mode
ADC0 ~ ADC3
Differential input channels are the paired channels
Differential input paired channel
Single-end input channel 1 2 3 4 5 6 7

10. ADC Clock Source
NUC100

11. ADC Clock Selection (in SYS_init.c)
void CLK_SetModuleClock(
uint32_t u32ModuleIdx,
uint32_t u32ClkSrc,
uint32_t u32ClkDiv)
ADC Clock Source
CLK_CLKSEL1_ADC_S_HXT
CLK_CLKSEL1_ADC_S_LXT
CLK_CLKSEL1_ADC_S_PLL
CLK_CLKSEL1_ADC_S_HCLK
CLK_CLKSEL1_ADC_S_HIRC
ADC Clock Divider
CLK_CLKDIV_ADC(x)
Module Index = ADC
Clock Source
Clock Divider
ADC clock 8-bit divider = x

12. ADC Sample Modes
Single Mode
Single-Cycle Mode
Continuous Mode

13. ADC Single mode

14. ADC Single-Cycle mode

15. ADC Continuous mode

16. ADC Initialization (in adc.c)
void ADC_Open(ADC_T *adc,
uint32_t u32InputMode,
uint32_t u32OpMode,
uint32_t u32ChMask)
ADC input mode
ADC_INPUT_MODE_SINGLE_END
ADC_INPUT_MODE_DIFFERENTIAL
ADC operation mode
ADC_OPERATION_MODE_SINGLE
ADC_OPERATION_MODE_SINGLE_CYCLE
ADC_OPERATION_MODE_CONTINUOUS
ADC struct pointer
ADC input mode
ADC operation mode
ADC channel

17. NuMicro Cortex-M0 Learning Board
ADC reference voltage is VCC33 (3.3V)
ADC0~7(GPA0~7)
VR1

18. ADC Sample Codes ADC : Single Cycle Conversion
ADC_8ch : Continuous Conversion
ADC_Photoresistor : ADC0 reading sensors (GL5516, MQ7, UVM30)
ADC_Thermistor : ADC1 reading thermistor & calculate temperature
ADC_Joystick : ADC0 & ADC1 reading Joystick

19. ADC (Single Cycle Mode)
MCU_init.h (chip initialization setting)
//Define Clock source
#define MCU_CLOCK_SOURCE
#define MCU_CLOCK_SOURCE_HIRC // HXT, LXT, HIRC, LIRC
#define MCU_CLOCK_FREQUENCY //Hz
//Define MCU Interfaces
#define MCU_INTERFACE_ADC
#define ADC_CLOCK_SOURCE_HIRC // HXT, LXT, PLL, HIRC, HCLK
#define ADC_CLOCK_DIVIDER 1
#define PIN_ADC_0
#define PIN_ADC_1
#define PIN_ADC_2
#define PIN_ADC_3
#define ADC_CHANNEL_MASK ADC_CH_0_MASK | ADC_CH_1_MASK | ADC_CH_2_MASK | ADC_CH_3_MASK
#define ADC_INPUT_MODE ADC_INPUT_MODE_SINGLE_END // SINGLE_END, DIFFERENTIAL
#define ADC_OPERATION_MODE ADC_OPERATION_MODE_SINGLE_CYCLE // SINGLE, SINGLE_CYCLE, CONTINUOUS
CPU clock maximum frequency
ADC Single Cycle Conversion

20. ADC volatile uint8_t u8ADF; void ADC_IRQHandler(void) {
ADC Flag for main loop to detect when ADC sample finished
and ADC interrupt is generated
volatile uint8_t u8ADF;
void ADC_IRQHandler(void) {
uint32_t u32Flag;
// Get ADC conversion finish interrupt flag
u32Flag = ADC_GET_INT_FLAG(ADC, ADC_ADF_INT);
if(u32Flag & ADC_ADF_INT) u8ADF = 1;
ADC_CLR_INT_FLAG(ADC, u32Flag); }
Set ADC software flag when IRQ ocurrs

21. ADC void Init_ADC(void) {
ADC_Open(ADC, ADC_INPUT_MODE, ADC_OPERATION_MODE, ADC_CHANNEL_MASK); // set ADC modes & channels
ADC_POWER_ON(ADC); // Power on ADC
ADC_EnableInt(ADC, ADC_ADF_INT); // Enable ADC ADC_IF interrupt
NVIC_EnableIRQ(ADC_IRQn); // Enable CPU NVIC }
Define in MCU_init.h

22. ADC int32_t main (void) { int i; uint32_t u32Result; SYS_Init();
Init_ADC();
%dHz\n", SystemCoreClock);
u8ADF = 0;
while(1) {
ADC_START_CONV(ADC); // start ADC conversion
while (u8ADF == 0); // wait for ADC sampling finished & generate interrupt to set this flag to 1
// read ADC result & print it
for (i=0; i<4; i++) {
u32Result = ADC_GET_CONVERSION_DATA(ADC, i);
printf("ADC%d = %d, ",i, u32Result); }
printf("\n");
u8ADF =0; // clear the flag
start ADC conversion
Check flag from ADC IRQHandler
clear ADC software flag when ADC result is printed

23. ADC_4ch (Continuous Mode)
MCU_init.h (chip initialization setting)
//Define Clock source
#define MCU_CLOCK_SOURCE
#define MCU_CLOCK_SOURCE_HIRC // HXT, LXT, HIRC, LIRC
#define MCU_CLOCK_FREQUENCY //Hz
//Define MCU Interfaces
#define MCU_INTERFACE_ADC
#define ADC_CLOCK_SOURCE_HIRC // HXT, LXT, PLL, HIRC, HCLK
#define ADC_CLOCK_DIVIDER 1
#define PIN_ADC_0
#define PIN_ADC_1
#define PIN_ADC_2
#define PIN_ADC_3
#define ADC_CHANNEL_MASK ADC_CH_0_MASK | ADC_CH_1_MASK | ADC_CH_2_MASK | ADC_CH_3_MASK
#define ADC_INPUT_MODE ADC_INPUT_MODE_SINGLE_END // SINGLE_END, DIFFERENTIAL
#define ADC_OPERATION_MODE ADC_OPERATION_MODE_CONTINUOUS // SINGLE, SINGLE_CYCLE, CONTINUOUS
CPU clock maximum frequency
ADC Continuous Conversion
Mini51/54/58 only support Single mode conversion

24. ADC_4ch volatile uint32_t u32ADCvalue[4]; void ADC_IRQHandler(void) {
uint8_t i;
uint32_t u32Flag;
// Get ADC conversion finish interrupt flag
u32Flag = ADC_GET_INT_FLAG(ADC, ADC_ADF_INT);
if(u32Flag & ADC_ADF_INT) {
for (i=0; i<4; i++) {
u32ADCvalue[i] = ADC_GET_CONVERSION_DATA(ADC, i);
printf("ADC%d = %4d, ",i, u32ADCvalue[i]); }
printf("\n");
ADC_CLR_INT_FLAG(ADC, u32Flag);
check ADC interrupt flag
read ADC value
clear ADC interrupt flag

25. ADC_4ch void Init_ADC(void) {
ADC_Open(ADC, ADC_INPUT_MODE, ADC_OPERATION_MODE, ADC_CHANNEL_MASK);
ADC_POWER_ON(ADC);
ADC_EnableInt(ADC, ADC_ADF_INT);
NVIC_EnableIRQ(ADC_IRQn);
ADC_START_CONV(ADC); }
int32_t main (void)
SYS_Init();
Init_ADC();
while(1);
start ADC conversion once when using Continous Mode
When ADC finish its conversion, ADC interrupt will occur,
ADC_IRQHandler will print out ADC value

26. Gas Sensor

27. CO gas sensor - MQ7

28. CO gas sensor - MQ7 CO

29. UV Sensor - UVM-30

30. IR Ranger - GP2Y0A41SK0F
0.4V ~ 3V
30cm ~ 3cm
every 5ms

31. IR Ranger : Distance vs Output voltage

32. Photoresistor (GL5516)

33. Photoresistor Connection Diagram
Learning Board
Vcc3.3V
pullup resistor 10Kohm
Measure the resistance for calibration in main.c
ADC6
(GPA6)
Photoresistor
0~10Kohm
Gnd
Sample Code : ADC_Photoresistor

34. ADC_Photoresistor get ADC value & print it
void ADC_IRQHandler(void) { uint32_t u32Flag; uint32_t u32ADCvalue; // Get ADC conversion finish interrupt flag u32Flag = ADC_GET_INT_FLAG(ADC, ADC_ADF_INT); if(u32Flag & ADC_ADF_INT) { u32ADCvalue = ADC_GET_CONVERSION_DATA(ADC, 0); printf("ADC0= %4d\n",u32ADCvalue); } ADC_CLR_INT_FLAG(ADC, u32Flag);
get ADC value & print it

35. ADC_Photoresistor define in MCU_init.h
void Init_ADC(void) { ADC_Open(ADC, ADC_INPUT_MODE, ADC_OPERATION_MODE, ADC_CHANNEL_MASK); ADC_POWER_ON(ADC); ADC_EnableInt(ADC, ADC_ADF_INT); NVIC_EnableIRQ(ADC_IRQn); ADC_START_CONV(ADC); } int32_t main (void) SYS_Init(); Init_ADC(); printf("ADC ch0 reading sensor\n"); while(1);
define in MCU_init.h

36. Thermistor NTC Thermistor : Negative Temperature Coefficient
temperature rising will decrease resistance
B or β parameter equation
log(R) = log(R0) + B * (1/T – 1/T0)
1/T = 1/T0 + (log(R) – log(R0)) / B
T = 1 / (1/T0 + (log(R) – log(R0)) /B)
Temperature Calculation

37. Thermistor Connection Diagram
Learning Board
Vcc3.3V
pullup resistor 10Kohm
Measure the resistance for calibration in main.c
ADC6
(GPA6)
thermistor
0~10Kohm
Gnd
Sample Code : smpl_ADC_Thermistor

38. ADC_Thermistor
thermistor
pullup
resistor

39. ADC_Thermistor Resistance to Temperature calculation
void Thermistor(int16_t ADCvalue) { double T, Temp; double T0 = ; // double lnR; int16_t R; // Thermistor resistence int16_t R0 = 8805; // calibrated by reading R at 28 degree celsius int16_t B = 3950; int16_t Pullup = 9930; // 10K ohm // R / (Pullup + R) = adc / 4096 R = (Pullup * ADCvalue) / ( ADCvalue); // B = (log(R) - log(R0)) / (1/T - 1/T0) T = 1 / (1/T0 + (log(R)-log(R0)) / B ); Temp = T ; printf("ADC:%4d, R=%d, Temp.=%f\n", ADCvalue, R, Temp); }
Resistance to Temperature
calculation

40. ADC_Joystick

41. ADC_Joystick using 2 channels AD0 & ADC1 to read joystick X & Y value
void ADC_IRQHandler(void) { uint32_t u32Flag; u32Flag = ADC_GET_INT_FLAG(ADC, ADC_ADF_INT); if(u32Flag & ADC_ADF_INT) { X = ADC_GET_CONVERSION_DATA(ADC, 0); Y = ADC_GET_CONVERSION_DATA(ADC, 1); } ADC_CLR_INT_FLAG(ADC, u32Flag); void Init_ADC(void) ADC_Open(ADC, ADC_INPUT_MODE, ADC_OPERATION_MODE, ADC_CHANNEL_MASK ); ADC_POWER_ON(ADC); ADC_EnableInt(ADC, ADC_ADF_INT); NVIC_EnableIRQ(ADC_IRQn); ADC_START_CONV(ADC);
using 2 channels AD0 & ADC1 to read joystick X & Y value

42. PWM Trigger ADC Sampling

43. ADC Conversion Trigger Sources (Nano100)

44. ADC Driver function call (adc.c)
void ADC_EnableHWTrigger(ADC_T *adc,
uint32_t u32Source,
uint32_t u32Param)
ADC HW Trigger Source
ADC_ADCR_TRGS_STADC
ADC_ADCR_TRGS_PWM
ADC STADC Trigger Mode
ADC_ADCR_TRGCOND_LOW_LEVEL
ADC_ADCR_TRGCOND_HIGH_LEVEL
ADC_ADCR_TRGCOND_FALLING_EDGE
ADC_ADCR_TRGCOND_RISING_EDGE
ADC struct pointer
ADC HW Trigger Source
ADC STADC Trigger Mode
Triggered by External pin STADC
Triggered by PWM

45. Project : Plant Care Function : use ADC to read Moisture & pH
Platform :
Example :
Demo :

46. Important Notice !
This educational material are neither intended nor warranted for usage in systems or equipment, any malfunction or failure of which may cause loss of human life, bodily injury or severe property damage. Such applications are deemed, “Insecure Usage”.
Insecure usage includes, but is not limited to: equipment for surgical implementation, atomic energy control instruments, airplane or spaceship instruments, the control or operation of dynamic, brake or safety systems designed for vehicular use, traffic signal instruments, all types of safety devices, and other applications intended to support or sustain life.
All Insecure Usage shall be made at user’s own risk, and in the event that third parties lay claims to the author as a result of customer’s Insecure Usage, the user shall indemnify the damages and liabilities thus incurred by using this material.
Please note that all lecture and sample codes are subject to change without notice. All the trademarks of products and companies mentioned in this material belong to their respective owners.

47. References
Analog-to-digital converter - Wikipedia, the free encyclopedia
Flash ADC - Wikipedia, the free encyclopedia
Understanding SAR ADCs: Their Architecture and Comparison with ...
TI High Speed Analog to Digital Converter Basics

48. Digital to Analog Converter (DAC)
Binary-Weighted Resistor DAC
ΔΣ DAC (Sigma-Delta DAC)
R-2R Ladder DAC
Vout =   - (Vmsb + Vn + Vlsb) = - (Vref + Vref/2 + Vref/ 4)