PIC Microcontroller | ADC Interfacing

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PIC Microcontroller
Prof. Ashvini Kulkarni
Assistant Professor
Department of Electronics & Telecommunication
Hope Foundation’s
International Institute of Information Technology, I²IT
www.isquareit.edu.in

 Characteristics of ADC
 PIC 18 ADC features
 PIC 18 ADC control registers
Hope Foundation’s International Institute of Information Technology, I²IT, P-14 Rajiv Gandhi Infotech Park, Hinjawadi, Pune - 411 057
Tel - +91 20 22933441 / 2 / 3 | Website - www.isquareit.edu.in ; Email - info@isquareit.edu.in
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 Analog signal is converted into a digital data that
can be processed using a digital computer.
 Types of ADC:
 Slope and double-slope type
 Flash type
 Successive approximation
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 Characteristics of ADC[2]:
1. Resolution:
 ADC has n- bit resolution(where n=8,10,12,16,24
bits)
 Higher the resolution smaller the step size
 If ADC has 8 bit resolution means 2^8= 256(No. of
steps)
 Applied voltage is Vref=5v then 5/256=19.53 mv
(step size)
2. Conversion time:
 The time it takes for the converting analog input to
digital output Vref:It is input voltage used for the
reference voltage
 Vref/no. of steps(Vref is responsible for step size)
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 Characteristics of ADC:
3. Digital data output:
 8 bit ADC, we have 8bit digital data output of D0
–D7
 Dout=Vin/step size[2]
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 Features of ADC
1) The ADC in PIC18F4550 is a successive
approximation ADC with a resolution of 10 bits.
2) It has 10 input channels.
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Configuring Registers
Tel - +91 20 22933441 / 2 / 3 | Website - www.isquareit.edu.in ; Email - info@isquareit.edu.in7
The PIC18 Microcontroller
- The A/D converter has the following
registers[1]:
• A/D Control Register 0 (ADCON0)
• A/D Result High Register (ADRESH)
• A/D Result Low Register (ADRESL)

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Figure No. 1: Block diagram of ADC in PIC18f4550[1]

 Each port pin associated with the A/D
converter can be configured as an
analog input or as a digital I/O.
 When the A/D conversion is complete,
the result is loaded into the
ADRESH:ADRESL registers,
 the GO/DONE bit (ADCON0 register) is
cleared and A/D Interrupt Flag bit,
ADIF, is set.
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 The analog reference voltage is
software selectable to either the
device’s positive and negative supply
voltage (VDD and VSS) or the voltage
level on the RA3/AN3/VREF+ and
RA2/AN2/VREF-/CVREF pins.
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1. Configure the A/D module: Configure analog pins,
voltage reference and digital I/O (ADCON1)
 Select A/D input channel (ADCON0)
 Select A/D acquisition time (ADCON2)
 Select A/D conversion clock (ADCON2)
 Turn on A/D module (ADCON0)
2. Configure A/D interrupt (if desired):
 Clear ADIF bit
 Set ADIE bit
 Set GIE bit
3. Wait the required acquisition time (if required).
 Start conversion
 Set GO/DONE=1 bit in (ADCON0 register)
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5. Wait for A/D conversion to complete, by either:
 Polling for the GO/DONE bit to be cleared OR Waiting
for the A/D interrupt
6. Read A/D Result registers (ADRESH:ADRESL);
 clear bit ADIF, if interrupt bit is set.
7. For next conversion, go to step 1 or step 2, as
required.
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[1] Microchip datasheet of PIC18F2455/2550/4455/4550
[2] Muhamad Ali Mazidi,Rolind D Mckinly,”PIC
microcontroller and embedded systems”Pearson
publication.
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For further information please contact
Ashvini Kulkarni
Department of Electronics & Telecommunication
Hope Foundation’s International Institute of
Information Technology, I²IT
Hinjawadi, Pune – 411 057
Phone - +91 20 22933441
www.isquareit.edu.in | ashvinik@isquareit.edu.in
| info@isquareit.edu.in
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PIC Microcontroller | ADC Interfacing

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