PIC microcontroller tutorial

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PIC microcontroller is very convenient choice to get started with a microcontroller projects. In this tutorial we will study:

• an introduction to PIC microcontrollers
• how to choose the right PIC microcontroller
• ideas for PIC microocntroller projects

PIC microcontroller introduction

A Microcontroller is an inexpensive single-chip computer. The microcontroller’s most important feature is its capabilities of STORING and RUNNING a program.

Every Microcontroller (also MCU) consists of several major units:

• Input / Output Ports
• Control Pins: reset, power, clock
• Processor (CPU)
• Memory (RAM, ROM, EEPROM)
• Serial and parallel ports
• Timers
• Analog-to-digital (A/D) and digital-to-analog (D/A) converters

Characteristics of the RISK (Reduce Instruction Set Control) system:

• Instruction set of 35 commands
• Instructions are carried out in 2 clock cycles
• You can calculate the execution time of the command in accordance with the frequency clock (if the frequency clock is 20Mhz, execution time of a command is 200ns)
• The ports of 28/40/44 pins microcontrollers are the same

Microcontrollers PICmicro MCU from Microchip Company divided into 4 large families. Each family has a variety of components that provide built-in special features:

1. The first family, PIC10 (10FXXX) - is called Low End.
   The PIC10FXXX devices from Microchip Technology are low-cost, high-performance, 8-bit, fully static, Flash-based CMOS microcontrollers. They employ a RISC architecture with only 33 single-word/ single-cycle instructions. The 12-bit wide instructions are highly symmetrical. The easy-to-use and easy to remember instruction set reduces development time significantly. The PIC10FXXX devices contain an 8-bit ALU and working register.


2. The second family, PIC12 (PIC12FXXX)– is called Mid-Range.
   The PIC12FXXX most popular among these starter their way in this field. Mid-Range devices feature 14-bit program word architecture and are available in 8 to 64-pin packages that offer an operating voltage range of 1.8-5.5V, small package footprints, interrupt handling, an 8-level hardware stack, multiple A/D channels and EEPROM data memory. Mid-range devices offer a wide range of package options and a wide range of peripheral integration. These devices feature various serial analog and digital peripherals, such as: SPI, I2C™, USART, LCD and A/D converters.
3. The third family is PIC16(16FXXX).
   With six variants ranging from 3.5K-14 Kbytes of Flash memory, up to 256 bytes of RAM and a mix of peripherals including EUSART, CCP and onboard analog comparators. These devices are well suited for designers with applications that need more code space or I/O than 14-pin variants supply, and are looking to increase system performance and code efficiency by employing hardware motor control and communications capability.
4. The fourth family is PIC 17/18(18FXXX).
   The PIC18 family utilizes a 16-bit program word architecture and incorporates an advanced RISC architecture with 32 level-deep stack, 8x8 hardware multiplier, and multiple internal and external interrupts. With the highest performance in Microchip’s 8-bit portfolio, the PIC18 family provides up to 16 MIPS and linear memory. PIC18 is the most popular architecture for new 8-bit designs where customers want to program in C language.

CLICK here to learn more about PIC microcontrollers from Microchip

How to choose/select a PIC microcontroller

Each type of PIC microcontroller provides a different combination of features, thus the most suitable can be selected for any given application. Some of the main selection criteria are:

• number of I/O pins availbale
• program memory size
• program memory type (ROM, EPROM, Flash)
• EEPROM data memory
• timers (8-bit or 16-bit), CCP
• interrupt sources
• analog inputs (8-bit or 10-bit)
• serial communication interfaces (USART, SPI, I2C, CAN)
• internal oscillator
• in-circuit debugging
• package (DIP, SOIC, PLCC, QFP)
• price

When developing an embedded system, the number and type of inputs and outputs need to be determined. After the hardware requirements have been established, the program need to be written and tested. Once the size of the program known, the chip memory size can be determined.
The following table is the summary information for selected PIC flash microcontrollers as a guide to the features available:

PIC #	# of pins	I/O pins	Program ROM words	File RAM bytes	EEPROM bytes	Analogue inputs	Timers 8/16 bits	Max clock (MHz)	Internal osc. (MHz)	In-circuit debug	Serial comms
12F675	8	6	1k	64	128	4x10-bit	1/1	20	4	YES	NO
16F628A	18	16	2k	224	128	NO	2/1	20	4	NO	UART
16F630	14	12	1k	64	128	NO	1/1	20	4	YES	NO
16F648A	18	16	4k	256	256	NO	2/1	20	4	NO	UART
16F676	14	12	1k	64	128	8x10-bit	1/1	20	4	YES	UART
16F73	28	22	4k	192	NO	5x8-bit	2/1	20	NO	NO	ALL
16F77	40	33	8k	368	NO	8x8-bit	2/1	20	NO	NO	ALL
16F818	18	16	1k	128	128	5x10-bit	2/1	20	8	YES	I2C,SPI
16F84	18	13	1k	64	64	NO	1/0	10	NO	NO	NO
16F84A	18	13	1k	64	64	NO	1/0	20	NO	NO	NO
16F88	18	16	4k	368	256	7x10-bit	2/1	20	8	YES	ALL
16F874A	40	33	4k	192	128	8x10-bit	2/1	20	NO	YES	ALL
16F876A	28	22	8k	256	368	5x10-bit	2/1	20	NO	YES	ALL
16F877A	40	33	8k	256	368	8x10-bit	2/1	20	NO	YES	ALL
18F2320	28	25	4k	512	256	10x10-bit	1/3	40	8	YES	ALL
18F6520	64	52	16k	2048	1024	12x10-bit	1/3	40	NO	YES	ALL
18F8621	80	68	32k	3840	1024	16x8-bit	1/3	40	10	YES	I2C,SPI
18F8720	80	68	64k	3840	1024	16x10-bit	1/3	40	NO	YES	ALL

Source: "PIC microcontrollers" by Martin Bates

The PIC16 family is the most common used family from the PIC families. Compared to PIC 17/18 families, the PIC16 family are easy to study and can be used to create “smart” applications.

The great advantage of this PIC is a Flash memory, allowing to burn to the memory unlimited number of times. You can write the program and burn it to the memory inside the microcontroller.

You conduct a test of what was written on the assembled circuit. If you find a mistake or want to make another change in the program, after the change, you can burn the new program once again to the same microcontroller. During the burning process, the old program is deleted, and instead the new program is burned to the FLASH memory. This process can be to done tens of thousands of times. Another advantage is that the price is low.

Examples of applications and some ideas for educational projects that are based on PIC microcontroller

The PIC microcontrollers are widely used in industry and education fields (projects, labs). In fact, almost any systems where there is a need to control certain processes, to obtain information from external sources, and interpret collected information, the microcontrollers is used.

For example, the ABS (an Anti-lock Braking System) is a safety system which prevents the wheels on a motor vehicle from locking while braking, includes a microcontroller. Likewise, all electronics devices in the household are based on microcontrollers, because there is need to monitor certain processes or perform some actions.

"Car with remote control” - This project includes a simple transmitter and receiver. One microcontroller is located inside the car and the other inside the remote.

"Voice recognition" – This project includes a microcontroller with A/D converter. Let’s assume the user records a name and the phone number. The information will be converted to digital information and will be stored in the memory. At any time, the user can speak up the desire name and microcontroller, after recognizing the name, will display the phone number.

"Smart Car" - This project includes two sensors. The 2 sensors are connected to the microcontroller and transmitting a comprehensive data on:

• fuel consumption
• a distance to travel relatively to the fuel consumption
• elapsed trip time
• a trip distance

All the information can be displayed on the LCD.