Microcontroller part 6_v1

https://www.facebook.com/groups/embedded.system.KS/

Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Embedded System

PART 6 (ADC)ENG.KEROLES SHENOUDA

1










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC

“Analog Digital Converter”

2










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC introduction

Signals in the real world are analog: light, sound, you name it. So, real-world signals must be converted into digital, using a circuit called ADC (Analog-to-Digital Converter)

3










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC introduction4

01001010Register

Sampling period

Sensor Output










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemADC Application: Embedded systems

receive

Embedded systems receive their inputs from the external world in the form of analog signals.

An analog signal (amplitude varies continuously) needs to be converted into a digital signal as processor only takes digital signals ( a series of ones and zerosrepresented by voltages).

Thus conversions are performed by Analog-to-Digital(ADC) and the reverse conversion of digital to analog by Digital-to-Analog(DAC).

5










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Signals ConceptTO UNDERSTAND THE ADC #IN_DEPTH, YOU SHOULD UNDERSTAND WELL

THE FOLLOWING CONCEPTS

6










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Signals7










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Concepts: Embedded Communication “PCM”s

Modulation

Analog Modulation Digital Modulation

Continues WavePulse Modulation

AMFM

PM

PAM

PWM PPMPCM

8










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sampling (Hand writing)

time domain

Theoretical Sampling: x(t). ð(t-t.)

x(t) Ks(t)

P(t) periodic impulse train

9










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sampling (Hand writing)10










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemSampling(Handwriting)

Frequency Domain11










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

quantizer

Vmax

Vmix

12










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

quantizer

Quantizer_max_error = 2

13










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemDeterministic Sawtooth Waveform

Error Model14










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

quantizer15










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system16

01011111










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Quantizer Types

Quantizer

Uniform Quantizer

midrise quantizer midtead quantizer

Non-uniform quantizer

17










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Now Simply we can

consider ADC as…?

18










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Simply we can consider ADC as

ADC major characteristicsConversion TimeResolutionVrefParallel vs. serialInput channels

19

Analog Signal Sampler Quantizer Encoder










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ResolutionAnalog Signal

20Assume ADC resolution 1 bit That mean that the ADC Register have two value 1 or 0










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system



Number of levels = 2^1 = 2 two levelsStep size = Vref / 2 = 2.5

Low Level =0

High Level =1

Step size

Step size










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system




Low Level =0

High Level =1

Step size

Step size

Assume sampling this value










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system




Low Level =0

High Level =1

Step size

Step size

Assume sampling this value










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system












Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system



Number of levels = 2^2 = 4 levelsStep size = Vref / 4 = 1.25 v

Step size =1.25










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Resolution26










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemResolution at constant

Vref = (Vmax-Vmin) = 5 27










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Define The Resolution?

28










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system29Resolution

ADC voltage resolution ADC resolution

The resolution of the converter indicates the number of discrete values it can produce over the range of analog values. If this variable uses eight bits, this means it can hold values from 0 to 255 (2^8 = 256). If this variable uses 16 bits, this means it can hold values from 0 to 65,535 (2^16 = 65,536). And so on.

ADC voltage resolution == Step size

The ADC voltage resolution is the

smallest change in input that can be

reliably detected by the system.

ResolutionThe ADC has n-bit resolution, where n can be 8, 10, 12, 16, or even 24 bits. Higher-resolution ADCs provide a smaller step size, where step size is the smallest change that can be discerned by an ADC.Although the resolution of an ADC chip is decided at the time of its design and cannot be changed, we can control the step size with the help of what is called Vref.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Example

assume input signal x(t) = Acos(t), A = 5V

Full scale measurement range = -5 to 5 volts

ADC resolution is 8 bits

Calculate ADC voltage resolution……?

30









https://en.wikipedia.org/wiki/Full_scale


Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Solution

(assume input signal x(t) = Acos(t), A = 5V)

Full scale measurement range = -5 to 5 volts

ADC resolution is 8 bits: 28 = 256 quantization levels (codes)

ADC voltage resolution, Q = (5 V − (-5) V) / 256 = 10 V / 256 ≈ 0.039 V ≈ 39 mV.

31









https://en.wikipedia.org/wiki/Full_scale


Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Major Characteristics of the ADC

Conversion Time

Conversion time is defined as the time it takes the ADC to convert the analog input to a digital (binary) number.

The conversion time is dictated by the clock source connected to the ADC in addition to the method used for data conversion and technology used in the fabrication of the ADC chip such as MOS or TTL technology.

Reference Voltage ( Vref )

Vref is an input voltage used for the reference voltage.

The voltage connected to this pin, along with the resolution of the ADC chip, dictate the step size.

For an 8-bit ADC, the step size is Vref/256 because it is an 8-bit ADC, and 2 to the power of 8 gives us 256 steps.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system


Digital data output

In an 8-bit ADC we have an 8-bit digital data output of D0-D7, while in the 10-bit ADC the data output is D0-D9.

To calculate the output voltage, we use the following formula:

Dout = Vin / step size

Where

Dout = digital data output (in decimal),

Vin = analog input voltage

step size = (resolution) is the smallest change, which is

( Vref / 256 ) for an 8-bit ADC.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Simple Quiz

34










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system











Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system











Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Signal to Noise ratio SNR

37

Conclusion










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR38

power










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR39

power

Voltage










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR40

power

Voltage

power Voltage

dBpower










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR41

power

Voltage

power Voltage

dBpower

dBVoltage










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR42

power

Voltage

power Voltage

dBpower

dBVoltage

If










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

SNR

The signal-to-noise ratio (SNR), which measures the noise level, can be easily calculated through this formula, where n is the number of bits used on the ADC:SNR = 6.02 x n + 1.76 dB

The higher the SNR, the better. An 8-bit ADC provides a SNR of 49.9 dB, while a 16-bit SNR provides a SNR of 98 dB (which is, by the way, a virtually no-noise value).

43










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system44

Conclusion










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Conclusion45

Analog Signal Sampler Quantizer Encoder










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Conclusion46Analog

Signal Sampler Quantizer EncoderAnalog Signal Sampler

Sampling Time










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Conclusion47Analog

Signal Sampler Quantizer EncoderAnalog Signal Quantizer










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Conclusion48Analog

Signal Sampler Quantizer EncoderAnalog Signal Encoder










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

In your opinion how the Accuracy

of an ADC can be improved ?

49










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

By increasing 50










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Types

51










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Types

Parallel design (also known as Flash ADC);

Digital-to-Analog Converter-based design (e.g., ramp counter, successive approximation, tracking);

Integrator-based design(e.g., single-slope, dual-slope);

Sigma-delta design(also known as delta-sigma, 1-bit ADC or oversampling ADC).

52










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Parallel Design

The Flash ADC, also called parallel ADC,

Use a series of comparatorsIt works by comparing the input voltage – i.e., the analog signal – to a reference voltage,which would be the maximum value achieved by the analog signal.For example, if the reference voltage is of 5 volts, this means that the peak of the analog signal would be 5 volts. On an 8-bit ADC when the input signal reached 5 volts we would find a 255 (11111111) value on the ADC output, i.e., the maximum value possible.

Then the voltage reference is lowered through a resistor network and other comparators added, so the input voltage (analog signal) can be compared to other values.

53










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Flash ADC54










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemParallel Design

Advantages/disadvantages

Although Flash ADC uses a very simple design, it requires a lot of components. The number of required comparers is 2^n-1, where n is the number of output bits. Thus for an eight-bit Flash ADC 255 comparers would be necessary, and for a 16-bit Flash ADC, 65,535!

On the other hand, Flash ADC is the fastest ADC type available. The digital equivalent of the analog signal will be available right away at it output (it will only have the propagation delay inserted by the logic gates) – hence the name “flash”.

Another advantage of Flash ADC is that you can create an ADC with non-linear output. Usually ADCs have a linear output, i.e., each digital number corresponds to a fixed voltage increase on the analog input. For example, on the 3-bit ADC shown above with a Vref of 5 V, each digital number would represent 625 mV (5 V / 2^3). So 0 V = 000, 0.625 V = 001, 1.250 V = 010 and so on up to 5 V = 111.

Since Flash ADC comparisons are set by a set of resistors, one could set different values for the resistors in order to obtain a non-linear output, i.e., one value would represent a different voltage step from the other values.

55










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemParallel Design

Advantages/disadvantages56










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

DAC-Based Designs

There are a few ways to design an ADC using a DAC as part of its comparison circuit

Ramp Counter ADC

Successive Approximation ADC

57










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Ramp counter ADC

Ramp counter ADC, also called digital ramp ADC. Vin is the analog input and Dn through D0 are the digital outputs. The control line found on the counter turns on the counter when it is low and stops the counter when it is high.

The basic idea is to increase the counter until the value found on the counter matches the value of the analog signal. When this condition is met, the value on the counter is the digital equivalent of the analog signal.

It requires a START pulse for each analog voltage you want to convert into digital

So the main problem with this circuit is that it is very slow, as it would require up to 2^n-1 clock cycles to convert each sample. For an eight-bit ADC, it would take up to 255 clock cycles to convert a single sample. For a 16-bit ADC it would take up to 65,535 clock cycles to convert one sample.

58










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Ramp counter ADC59










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Successive Approximation ADC

the successive approximation ADC starts first setting the MSB (most significant bit, on an eight-bit ADC it would be D7). In order to facilitate the explanations below, consider an eight-bit ADC.

The comparison between Vin and the DAC output will tell the control unit if this bit should remain set at 1 or should be set at 0, as the op amp will tell right away the control unit if the sample value is greater or lower than 128 (2^7). Then D6 is set to one, and from the comparison done by the op amp, the control unit will know if this bit should remain set or not. And so on.

The good thing about the successive approximation ADC is its speed. At the worst case it will find the correct digital value for the sample at n clock cycles

60










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Successive Approximation ADC61










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sigma-delta design

A delta sigma ADC or DAC always consists of a delta sigma modulator which produces the bitstream and a low pass filter.

62

Quantization Noise










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sigma-delta design

A delta sigma ADC or DAC always consists of a delta sigma modulator which produces the bitstream and a low pass filter.

63

Quantization Noise

The Negative feedbackIs responsible on subtract Noise from the input signal

Equivalent ~ to high pass filter










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

We can model that in this way64










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sigma-delta design65










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Sigma-delta design66










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemSigma-delta design

Signals within a First Order

Analog Modulator

67










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Modules on Different

Microcontrollers

68










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC on TM4C123G SOC

69










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system70










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC important Features on TivaC71










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Specs on TivaC72










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC73










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system74










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Sample Sequencers75










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system76










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Now, You feel like 77










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Don’t worry, we will make

a lot of labs and go through

TivaC ADC in depth in the

ARM-CortexM Sessions

78










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC on ATMEGA32

79










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Features in Atmega3280

To be professional

On Embedded You should read

the Specs by

yourself










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Type81










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

So the main features

It is a 10-bit ADC.

It has 8 analog input channels,

7 differential input channels, and

2 differential input channels with

optional gain of 10x and 200x.

The converted output binary data is

held by two special function regis-

ters called ADCL (A/D Result Low)

and ADCH (A/D Result High).

Because the ADCH:ADCL registers

give us 16 bits and the ADC data out is only 10 bits wide, 6 bits of the 16 are unused.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

So the main features

We have three options for Vref

Vref can be connected to

AVCC (Analog Vcc) Internal 2.56 V Reference

External AREF pin

The conversion time is dictated by the crystal frequency connected to the XTAL pins (Fosc) and ADPS0:2 bits.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system84










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Simple Quiz

85










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Simple Quiz86










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system87

Simple Quiz










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Interfacing Sensors•8 channel implies that there are 8 ADC pins are

multiplexed together. You can easily see that these pins

are located across PORTA (PA0…PA7).

•10 bit resolution implies that there are 2^10 = 1024

•the type of ADC implemented inside the AVR MCU is of

Successive Approximation type.

88










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Analog to

Digital

Converter

Block

Schematic

Operation

89










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

How it works

The analog voltage at the input of the ADC must be greater than 0V, and smaller than the ADC's reference voltage AREF.

The reference voltage is an external voltage you must supply at the Aref pin of the chip.

The value the voltage at the input is converted to can be calculated with the follwing formula:

ADC conversion value = round( (vin/vref)*1023)

Since it is a 10-bit ADC, you have 1024(1024=2^10) possible output values (from 0 to 1023). So, if vin is equal to 0V, the result of the conversion will be 0, if vin is equal to vref, it will be 1023, and if vin is equal to vref/2 it will be 512

90










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Modes of Operation

Single Conversion mode, you have to initiate each conversion. When it is

done, the result is placed in the ADC Data register pair and no new conversion is started.

In Free Runing mode, you start the conversion only once, and then, the ADC automatically will start the following conversion as soon as the previous one is finished

The analog to digital conversion is not instantaneous, it takes some time. This time depends on the clock signal used by the ADC. The conversion time is

proportional to the frequency of the ADC clock signal, which must be between 50kHz and 200kHz.

91










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Modes of Operation

If you can live with less than 10-bit resolution, you can reduce the conversion time by increasing the ADC clock frequency.

The ADC module contains a prescaler, which divides the system clock to an acceptable ADC clock frequency. You configure the division factor of the prescaler using the ADPS bits

92










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Modes of Operation

To know the time that a conversion takes, just need to divide the number of ADC clock cycles needed for conversion by the frequency of the ADC clock.

Normaly, a conversion takes 13 ADC clock cycles.

The first conversion after the ADC is switched on (by setting the ADEN bit) takes 25 ADC clock cycles. This first conversion is called an "Extended Conversion".

For instance, if you are using a 200kHz ADC clock signal, a normal conversion will take 65 microsenconds (13/200e3=65e-6), and an extended conversion will take 125 microseconds (25/200e3=125e-6).

93










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Registers

94










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Programming in AVR

In the AVR microcontroller five major registers are associated with the ADC They are

1. ADCH (high data)

2. ADCL (low data)

3. ADCSRA (ADC Control and Status Register)

4. ADMUX (ADC multiplexer selection register)

5. SPIOR (Special Function I/O Register).










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemADMUX – ADC Multiplexer Selection

Register96










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADMUX – ADC Multiplexer Selection

Register 97










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADCH and ADCL Data registers

ADCH:ADCL store the results of conversion.

The 10 bit result can be right or left justified:

ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADC1 ADC0 - - - - - -ADC9 ADC8

ADCH ADCL

ADLAR = 0

ADLAR =1

ADC7 ADC6 ADC5 ADC4 ADC3 ADC2 ADC1 ADC0- - - - - - ADC9 ADC8

ADCH ADCL










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADCSRA – ADC Control and Status

Register A

ADEN – ADC Enable – As the name says, it enables the ADC feature. Unless this is enabled,

ADC operations cannot take place across PORTA i.e. PORTA

will behave as GPIO pins.

ADSC – ADC Start Conversion –Write this to ‘1’ before starting any conversion. This 1 is written as long as the conversion is in

progress, after which it returns to zero. Normally it takes 13 ADC clock pulses for this operation. But when you call it for the first time, it takes 25 as it performs

the initialization together with it.

ADATE – ADC Auto Trigger Enable –Setting it to ‘1’ enables auto-triggering of ADC. ADC is triggered automatically

at every rising edge of clock pulse

ADIF – ADC Interrupt Flag –Whenever a conversion is

finished and the registers are updated, this bit is set to ‘1’

automatically

99










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADCSRA – ADC Control and Status

Register A

ADIE – ADC Interrupt Enable –

When this bit is set to ‘1’, the

ADC interrupt is enabled. This is

used in the case of interrupt-

driven ADC.

ADPS2:0 – ADC Prescaler

Select Bits – The prescaler

(division factor between XTAL

frequency and the ADC clock

frequency)

100










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemSFIOR – Special Function I/O

Register101










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Prescaling and Conversion Timing 102










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Timing Diagram, First Conversion (Single

Conversion Mode)

103










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Timing Diagram, Single Conversion 104










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Timing Diagram, Auto Triggered Conversion 105










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Timing Diagram, Free Running Conversion 106










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Why 13 cycles max used for

ADC Conversion time ? THINK IN-DEPTH

107










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Programming ADC108










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Lab 1 BY USING POLLING

109










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

ADC Lab1

make Port A an input for ADC input

using Polling

2.56V Vref internal, right justified,

make ADC enable and select CLK/128

select ADC Channel 0

ADC conversion value =

round( (vin/vref)*1023)

If Vin =2.65

The ADC value =round(2.65/2.56)*1023=1023=0x3ff

110










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system111










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemADC Lab2 the same as lab1 but

using Interrupt make Port A an input for ADC input

using Polling

2.56V Vref internal, right justified,

make ADC enable and select CLK/128

select ADC Channel 0

ADC conversion value =

round( (vin/vref)*1023)

If Vin =2.65

The ADC value =round(2.65/2.56)*1023=1023=0x3ff

112










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system113










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemThermistor dependent resistor

(DR) For example, the following thermistor circuit has

a resistance of 10KΩ at 25°C and a resistance of 100Ω at 100°C. Calculate the output voltage (Vout) for both temperatures

114










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

LM34 and LM35 Temprature Sensors

The output voltage is of LM34 is linearly proportional to the Fahrenheit temperature. It outputs 10 mV for each degree of Fahrenheit temperature.

Part Scale Temp. Range Accuracy OutputLM34A -50 F to +300 F +2.0 F 10 mV/FLM34 -50 F to +300 F +3.0 F 10 mV/FLM34CA -40 F to +230 F +2.0 F 10 mV/FLM34C -40 F to +230 F +3.0 F 10 mV/FLM34D -32 F to +212 F +4.0 F 10 mV/F

Table 13-9: LM34 Temperature Sensor Series Selection Guide










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

LM34 and LM35 Temprature Sensors

The output voltage is of LM35 is linearly proportional to the Celsius temperature. It outputs 10 mV for each degree of Centidgade temperature.

Table 13-9: LM35 Temperature Sensor Series Selection Guide

Part Temp. Range Accuracy Output ScaleLM35A -55 C to+150 C +1.0 C 10 mV/CLM35 -55 C to +150 C +1.5 C 10 mV/CLM35CA -40 C to +110 C +1.0 C 10 mV/CLM35C -40 C to +110 C +1.5 C 10 mV/CLM35D 0 C to +100C +2.0 C 10 mV/C










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

Interfacing the LM34, LM35 to the AVR

LM34 (or LM35) produces 10mV for every degree of temperature change and the ADC has 10-bit resolution with a maximum of 1024 steps.

if we use the step size of 10 mV, the Vout will be 10,240 mV (10.24 V) for full-scale output.

The maximum temperature sensed by the LM34 is 300 degrees F, and its highest is 3000mV (3.00V).

If we use the internal 2.56V reference voltage, the step sizewould be 2.56 V/1024 = 2.5 mV.

(10 mV/2.5 mV = 4) This is four times the real temperature

We can scale it by dividing it by 4 to get the real number for temperature










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system


Temp. (F) Vin (mV) # of steps Binary Vout(b9-bO) Temp, in Binary

0 0 0 00 0000 0000 0000 0000

1 10 4 00 0000 0100 0000 0001

2 20 8 00 0000 1000 0000 0010

3 30 12 00 0000 1100 0000 0011

10 100 20 00 0010 1000 0000 1010

20 200 80 00 0101 0000 0001 0100

30 300 120 00 0111 1000 0001 1110

40 400 160 00 1010 0000 0010 1000

50 500 200 00 1100 1000 0011 0010

60 600 240 00 1111 0000 0011 1100

70 700 300 01 0001 1000 0100 0110

80 800 320 01 0100 0000 0101 0000

90 900 360 01 0110 1000 0101 1010

100 1000 400 01 1001 0000 0110 0100

Table 13-11: Temperature vs. Vout for AVR with Vref = 2.56 V










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system











Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemLAB3: write a program for Reading and displaying temperature

The following points must be noted:

1. The LM34 (or LM35) is connected to Channel 0 (ADC0 pin).

2. The 10-bit output of the A/D is divided by 4 to get the real temperature.

3. To divide the 10-bit output of the A/D by 4 we choose the left-justified option and only read the ADCH register. It is same as shifting the result two bits right. See Next Example.










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system121










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

PIR SENSOR:

The PIR sensor detect only bodies (hot materials and living objects) in motions not the static ones. This sensor uses Infra red beam to detect the motion and only covers a certain space based on the sensor model, you should to go through the manufacturer datasheet to know about the range. This sensor module gives only two output states that is logic High 1 which is equivalent to 3.3 V and logic low 0 equivalent to 0 V.

122










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_systemGATEWAY CAR Parking Project 123










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

GATEWAY CAR Parking WORKING:

The PIR sensor is interfaced with Atmega32 AVR microcontroller to detect the motion around the environment. Atmega32 considers any voltage between 2V to 5V as logic high. Hence PIR sensor is directly interfaced to the input pin of the controller.

The circuit shown above will read the status of the output of the PIR sensor and the ADC will read the Value if the Value is less than 3 Volt that mean that the PIR detected the CAR so the gateway will opened and the 7-segement will count each car entered on the PARKING and the Buzzer will run, then the Gateway will closed after the car moved a way from GATEWAY and the Buzzer will be OFF.

124










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

The ADC Driver IN THE NEXT SESSION

125










Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system

References

http://www.hardwaresecrets.com/how-analog-to-digital-converter-adc-works/3/

http://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html

AVR Microcontroller and Embedded Systems: Using Assembly and C (Pearson Custom Electronics Technology) 1st Editionhttps://www.amazon.com/AVR-Microcontroller-Embedded-Systems-Electronics/dp/0138003319

Embedded Systems Engr. Rashid Farid Chishti

Chapter 13: ADC, DAC and Sensor Interfacing

126









http://www.hardwaresecrets.com/how-analog-to-digital-converter-adc-works/3/

http://www.beis.de/Elektronik/DeltaSigma/DeltaSigma.html

https://www.amazon.com/AVR-Microcontroller-Embedded-Systems-Electronics/dp/0138003319


Follow us

Press

here#LEARN_IN DEPTH

#Be_professional_in

embedded_system127









Engineering

Microcontroller part 6_v1