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Microcontroller part 6_v1
- 1. 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
- 2. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC “Analog Digital Converter” 2
- 3. https://www.facebook.com/groups/embedded.system.KS/ 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
- 4. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC introduction 4 01001010 Register Sampling period Sensor Output
- 5. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC 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 zeros represented 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
- 6. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Signals Concept TO UNDERSTAND THE ADC #IN_DEPTH, YOU SHOULD UNDERSTAND WELL THE FOLLOWING CONCEPTS 6
- 8. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Concepts: Embedded Communication “PCM”s Modulation Analog Modulation Digital Modulation Continues Wave Pulse Modulation AM FM PM PAM PWM PPM PCM 8
- 9. https://www.facebook.com/groups/embedded.system.KS/ 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
- 10. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Sampling (Hand writing) 10
- 14. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_systemDeterministic Sawtooth Waveform Error Model 14
- 17. https://www.facebook.com/groups/embedded.system.KS/ 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
- 18. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Now Simply we can consider ADC as…? 18
- 19. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Simply we can consider ADC as ADC major characteristics Conversion Time Resolution Vref Parallel vs. serial Input channels 19 Analog Signal Sampler Quantizer Encoder
- 20. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 20Assume ADC resolution 1 bit That mean that the ADC Register have two value 1 or 0
- 21. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 21Assume ADC resolution 1 bit That mean that the ADC Register have two value 1 or 0 Number of levels = 2^1 = 2 two levels Step size = Vref / 2 = 2.5 Low Level =0 High Level =1 Step size Step size
- 22. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 22Assume ADC resolution 1 bit That mean that the ADC Register have two value 1 or 0 Number of levels = 2^1 = 2 two levels Step size = Vref / 2 = 2.5 Low Level =0 High Level =1 Step size Step size Assume sampling this value
- 23. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 23Assume ADC resolution 1 bit That mean that the ADC Register have two value 1 or 0 Number of levels = 2^1 = 2 two levels Step size = Vref / 2 = 2.5 Low Level =0 High Level =1 Step size Step size Assume sampling this value
- 24. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 24 Assume ADC resolution 2 bit That mean that the ADC Register have two value 1 or 0
- 25. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Resolution Analog Signal 25 Assume ADC resolution 2 bit That mean that the ADC Register have two value 1 or 0 Number of levels = 2^2 = 4 levels Step size = Vref / 4 = 1.25 v Step size =1.25
- 27. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_systemResolution at constant Vref = (Vmax-Vmin) = 5 27
- 28. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Define The Resolution? 28
- 29. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system 29Resolution 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. Resolution The 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.
- 30. https://www.facebook.com/groups/embedded.system.KS/ 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
- 31. https://www.facebook.com/groups/embedded.system.KS/ 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
- 32. https://www.facebook.com/groups/embedded.system.KS/ 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.
- 33. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Major Characteristics of the ADC 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.
- 35. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Major Characteristics of the ADC
- 36. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Major Characteristics of the ADC
- 37. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Signal to Noise ratio SNR 37 Conclusion
- 40. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system SNR 40 power Voltage power Voltage dB power
- 41. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system SNR 41 power Voltage power Voltage dB power dB Voltage
- 42. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system SNR 42 power Voltage power Voltage dB power dB Voltage If
- 43. https://www.facebook.com/groups/embedded.system.KS/ 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
- 45. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Conclusion 45 Analog Signal Sampler Quantizer Encoder
- 46. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Conclusion 46Analog Signal Sampler Quantizer Encoder Analog Signal Sampler Sampling Time
- 47. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Conclusion 47Analog Signal Sampler Quantizer Encoder Analog Signal Quantizer
- 48. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Conclusion 48Analog Signal Sampler Quantizer Encoder Analog Signal Encoder
- 49. https://www.facebook.com/groups/embedded.system.KS/ 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
- 50. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system By increasing 50
- 52. https://www.facebook.com/groups/embedded.system.KS/ 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
- 53. https://www.facebook.com/groups/embedded.system.KS/ 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 comparators It 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
- 55. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Parallel 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
- 56. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_systemParallel Design Advantages/disadvantages 56
- 57. https://www.facebook.com/groups/embedded.system.KS/ 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
- 58. https://www.facebook.com/groups/embedded.system.KS/ 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
- 59. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Ramp counter ADC 59
- 60. https://www.facebook.com/groups/embedded.system.KS/ 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
- 61. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Successive Approximation ADC 61
- 62. https://www.facebook.com/groups/embedded.system.KS/ 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
- 63. https://www.facebook.com/groups/embedded.system.KS/ 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 feedback Is responsible on subtract Noise from the input signal Equivalent ~ to high pass filter
- 64. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system We can model that in this way 64
- 67. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Sigma-delta design Signals within a First Order Analog Modulator 67
- 68. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Modules on Different Microcontrollers 68
- 69. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC on TM4C123G SOC 69
- 71. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC important Features on TivaC 71
- 72. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Specs on TivaC 72
- 75. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Sample Sequencers 75
- 77. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Now, You feel like 77
- 78. https://www.facebook.com/groups/embedded.system.KS/ 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
- 79. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC on ATMEGA32 79
- 80. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Features in Atmega32 80 To be professional On Embedded You should read the Specs by yourself
- 82. https://www.facebook.com/groups/embedded.system.KS/ 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.
- 83. https://www.facebook.com/groups/embedded.system.KS/ 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.
- 88. https://www.facebook.com/groups/embedded.system.KS/ 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
- 89. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Analog to Digital Converter Block Schematic Operation 89
- 90. https://www.facebook.com/groups/embedded.system.KS/ 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
- 91. https://www.facebook.com/groups/embedded.system.KS/ 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
- 92. https://www.facebook.com/groups/embedded.system.KS/ 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
- 93. https://www.facebook.com/groups/embedded.system.KS/ 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
- 94. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Registers 94
- 95. https://www.facebook.com/groups/embedded.system.KS/ 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).
- 96. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_systemADMUX – ADC Multiplexer Selection Register 96
- 97. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADMUX – ADC Multiplexer Selection Register 97
- 98. https://www.facebook.com/groups/embedded.system.KS/ 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
- 99. https://www.facebook.com/groups/embedded.system.KS/ 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
- 100. https://www.facebook.com/groups/embedded.system.KS/ 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
- 101. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system SFIOR – Special Function I/O Register 101
- 102. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Prescaling and Conversion Timing 102
- 103. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Timing Diagram, First Conversion (Single Conversion Mode) 103
- 104. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Timing Diagram, Single Conversion 104
- 105. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Timing Diagram, Auto Triggered Conversion 105
- 106. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Timing Diagram, Free Running Conversion 106
- 107. https://www.facebook.com/groups/embedded.system.KS/ 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
- 109. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system ADC Lab 1 BY USING POLLING 109
- 110. https://www.facebook.com/groups/embedded.system.KS/ 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
- 112. https://www.facebook.com/groups/embedded.system.KS/ 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
- 114. https://www.facebook.com/groups/embedded.system.KS/ 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
- 115. https://www.facebook.com/groups/embedded.system.KS/ 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 Output LM34A -50 F to +300 F +2.0 F 10 mV/F LM34 -50 F to +300 F +3.0 F 10 mV/F LM34CA -40 F to +230 F +2.0 F 10 mV/F LM34C -40 F to +230 F +3.0 F 10 mV/F LM34D -32 F to +212 F +4.0 F 10 mV/F Table 13-9: LM34 Temperature Sensor Series Selection Guide
- 116. https://www.facebook.com/groups/embedded.system.KS/ 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 Scale LM35A -55 C to+150 C +1.0 C 10 mV/C LM35 -55 C to +150 C +1.5 C 10 mV/C LM35CA -40 C to +110 C +1.0 C 10 mV/C LM35C -40 C to +110 C +1.5 C 10 mV/C LM35D 0 C to +100C +2.0 C 10 mV/C
- 117. https://www.facebook.com/groups/embedded.system.KS/ 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 size would 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
- 118. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Interfacing the LM34, LM35 to the AVR 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
- 119. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system Interfacing the LM34, LM35 to the AVR
- 120. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system LAB3: 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.
- 122. https://www.facebook.com/groups/embedded.system.KS/ 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
- 123. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system GATEWAY CAR Parking Project 123
- 124. https://www.facebook.com/groups/embedded.system.KS/ 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
- 125. https://www.facebook.com/groups/embedded.system.KS/ Follow us Press here #LEARN_IN DEPTH #Be_professional_in embedded_system The ADC Driver IN THE NEXT SESSION 125
- 126. https://www.facebook.com/groups/embedded.system.KS/ 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 Edition https://www.amazon.com/AVR-Microcontroller-Embedded-Systems- Electronics/dp/0138003319 Embedded Systems Engr. Rashid Farid Chishti Chapter 13: ADC, DAC and Sensor Interfacing 126