PIC 12F/16F/18F quick start

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Contents

Features

  • 8bits, 20-48MHz (5-12MIPs), 5volts (lower voltages at reduced speed)
  • Huge selection of chips, many still in DIP packages. One of the most complete and full-featured families of microcontroller available on the market. Still manufacturing many "legacy" chips (eg the 16F84 circa 1993).
  • PICs use a Harvard architecture where code and data memory are separate, unlike the von Neumann architecture used by the Intel Pentium. PICs use a RISC instruction set with just 35 instructions. All instructions execute in one instruction cycle except for those that modify the program counter such as conditional branches and gotos which always need two cycles.
  • One inexpensive, cross-platform (Windows, Linux, Mac OS X) device (Microchip's PICkit 2, see eBay for clones) programs and debugs most PICs
  • Previously famous for a generous sampling program (now dead)

Reference

Development and programming

IDE and compilers

  • MPLAB X is Microchip's new cross-platform IDE and compilers for Windows, Linux, and Mac OS X.


We use Microchip's free demonstration compilers with MPLAB. The demo compilers have certain optimizations that expire after 60 days, but we don't use those anyway.

There are many third-party compilers covering C, BASIC, Forth, JAL and Pascal: See Resources below.

Programmers

  • PICkit 2 The hobbyist's choice. A powerful programmer and debugger with cross-platform programming software (Windows via the MPLAB IDE, standalone application and command line application; Linux - with source code; Mac OS X - with source code). Debugging is only available with the Windows MPLAB IDE software. Additional Windows-only software is freely available from the Microchip website for a UART Tool (use se the PICkit 2 for PIC MCU serial communications) and a Logic Tool Analyzer (use the PICkit 2 to capture digital waveforms in a circuit). The PICkit 2 can also be used to program microcontrollers without being attached to a computer (Programmer-To-Go feature). Since the release of the PICkit 3 in 2009 (see below) Microchip have hinted that they will not add support for newer microcontrollers, but this does not seem to have been the case to date. There is also a user-created tool, the PICkit 2 Device File Editor which makes it easy(ier) to add new devices yourself. Note that some device are not supported in the MPLAB IDE but require the use of the standalone PICkit 2 programming application.
  • PICkit 2 clones Microchip made the PICkit 2 schematic, firmware and software freely available from their website and this has encouraged a slew of Chinese clones and a small number of enhanced, more expensive, clones. See eBay for current clones, also check vendors' own websites which may be cheaper (but watch the shipping charges!).
  • PICkit 3 Beware the newer PICkit 3. It is more like an ICD2 rather than a PICkit 2. From a hardware viewpoint, the PICkit 3 is a hybrid of PICkit 2 and the ICD 2; from a software viewpoint, it is purely an ICD 2. None of the good software architecture of PICkit 2 has shown up in PICkit 3 (yet anyway). The UART Tool and the Logic Tool Analyzer Tool are not available for it. The only programming and debugging software available for it is the Windows MPLAB IDE. To top it off it costs more than the PICkit 2 for significantly less functionality. The only reason you might consider it is that Microchip has committed to support it for future microcontrollers.
  • ICD 2 Superseded by the newer, cheaper ICD 3 (see below). Avoid.
  • ICD 3 In-Circuit-Debugger. Faster programming than a PICkit, but 4 times more expensive (or more compared with PICkit 2 clones). Also requires the purchase of additional header boards with a special microcontroller for debugging some 8-, 14- and 18-pin PIC microcontrollers.

Build your own programmer

Bootloaders

PICs do not ship with a bootloader, but there are many that you can program yourself. After the bootloader is installed, a programmer is no longer needed for simple firmware updates.

Basic circuit

Quick-pic-basic.png

This is the most basic circuit required to program a PIC 18F2550. Most PICs require a similar minimum support circuit.

D1 is only needed by PICs that require a programming voltage greater than the power supply (see reset circuits below).

Power

  • PIC 12/16/18F run at 5volts, and lower voltages at reduced speed
  • Connect all the supply pins to power (Vdd) or ground (Vss). Don't forget the AVdd and AVss pins
  • Put a 0.1uF decoupling capacitor on each positive supply pin, and put it as close to the chip on your PCB as possible

Reset

Quick-pic-reset.png

  • Reset is the MCLR/VPP pin on PICs (MCLR=master clear, VPP=programming voltage)
  • Connect a resistor from MCLR to the supply voltage for normal operation, use 10Kohms for PIC 12/16/18
  • The programmer uses 12-13volts on MCLR to put PIC 12F/16F/18F in programming mode. Use a small diode (D1) between the supply voltage and resistor (R1) to protect the supply voltage from the 13volt programming voltage

Programming connections

PICs use a 5 wire programming connection called ICSP in PIC datasheets. This is the prefered pinout order, it's compatible with the PICkit:

  1. VPP/MCLR - This pin is also the PIC reset pin. Used to enter programming mode, and reset after programming
  2. Supply voltage (from programmer, or to programmer)
  3. Ground
  4. PGD - Program data, a bi-directional data pin (often PORTB7)
  5. PGC - Program clock (often PORTB6)

Programming a PIC usually requires connecting these five pins to a programmer.

Newer/larger PICs may have multiple pairs of PGC and PGD pins:

  • Connect any pair you like
  • You need to use the same pair (PGC2 and PGD2, for example)
  • It's usually best to check the errata to be sure the pair you chose actually works

Clock source

Most PICs have an internal oscillator that can be used as the clock source.

  • An external clock source, resonator, or crystal can be attached to the OSC1 (input) and OSC2 pins.
  • A secondary, low speed oscillator (T1OSO/T1OSI) is usually available for an external 32.768kHz crystal (real time clock).

Peripherals

IO

Different PIC pins can source/sink different amounts of current. These are some general rules, but be sure to verify the capabilities in the datasheet for the exact device (usually a table at the beginning of the IO section).

  • PORTA-D usually source/sink 25mA
  • Others sometimes less

USB

Quick-pic-usb-18F.png

  • 18F USB devices (5volt parts) - An internal 3.3volt regulator requires a 0.22uF capacitor on the VUSB pin (we use 2 x 0.1uF), no other connections to VUSB are required
  • All PIC USB peripherals have an internal resistors, no other support circuitry is required

Resources

See PIC Resources for more information, third party compilers, operating systems/kernels, hardware (development boards), other tutorials and online PIC programming books.