Introduction to the PIC32 - Revision history

Lynch: /* PIC32 Hardware Overview */

2010-03-23T18:29:31Z

PIC32 Hardware Overview

Lynch at 18:27, 23 March 2010

2010-03-23T18:27:03Z

Lynch at 09:57, 27 January 2010

2010-01-27T09:57:18Z

Lynch: /* PIC32 Hardware Overview */

2010-01-27T09:55:42Z

PIC32 Hardware Overview

Lynch: /* NU32 Development Board Overview */

2010-01-27T09:49:53Z

NU32 Development Board Overview

Lynch: /* PIC32 Programming in C */

2010-01-20T11:28:36Z

PIC32 Programming in C

Lynch: /* PIC32 Programming in C */

2010-01-20T11:27:58Z

PIC32 Programming in C

Lynch: /* PIC32 Programming in C */

2010-01-20T11:26:59Z

PIC32 Programming in C

Lynch: /* PIC32 Programming in C */

2010-01-20T11:23:56Z

PIC32 Programming in C

Lynch: /* PIC32 Programming in C */

2010-01-20T11:01:35Z

PIC32 Programming in C

@@ Line 9: / Line 9: @@
 [[Image:PIC32MX4XX-pinout.png|thumb|200px|Pinout of the PIC32MX4XX.|right]]
-Our PIC32MX460F512L features a max clock frequency of 80 MHz, 512K program memory (flash), 32K data memory (RAM), multiple interrupt sources and handling routines, 16 analog-to-digital input channels, many digital I/O channels (with outputs that can be configured for open-drain), USB 2.0, two I2C and two SPI synchronous serial communication modules, two UARTs for RS-232 or RS-485 asynchronous serial communication, five 16-bit counter/timers (configurable to give two 32-bit timers), five pulse-width modulation outputs, and a number of pins that can generate interrupts based on external signals, among other features.  This PIC has 100 pins, many (but not all) of which are used or broken out by the NU32 board.
+Our PIC32MX460F512L features a max clock frequency of 80 MHz, 512K program memory (flash), 32K data memory (RAM), multiple interrupt sources and handling routines, 16 10-bit analog-to-digital input channels, many digital I/O channels (with outputs that can be configured for open-drain), USB 2.0, two I2C and two SPI synchronous serial communication modules, two UARTs for RS-232 or RS-485 asynchronous serial communication, five 16-bit counter/timers (configurable to give two 32-bit timers), five pulse-width modulation outputs, and a number of pins that can generate interrupts based on external signals, among other features.  This PIC has 100 pins, many (but not all) of which are used or broken out by the NU32 board.
 To cram this much functionality into 100 pins, many of the pins serve multiple functions.  For example, pin 20 can serve as a comparator input, an analog input, a change notification input which can generate an interrupt when the pin changes state, or a digital input or output.  Which function a particular pin serves is determined by "Special Function Registers" (SFRs) that contain configuration bits specifying the desired use of the pin.  Typically your program sets these configuration bits at the beginning of execution, and the functions of the pins are fixed while your program runs.  (It is possible, though rarely needed, to change the configuration bits and change the function of pins on the fly.)

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 The [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2591 Microchip PIC32] is a family of complex and powerful microcontrollers that can be purchased for less than $10 in quantities of one.  This microcontroller offers many peripherals useful for mechatronics purposes, such as several channels for analog-to-digital conversion, digital I/O, synchronous and asynchronous serial communication, pulse width modulation, etc.  For our purposes, the primary advantages of the 32-bit PICs over the 8-bit PICs we have used (and will continue to use) are that they are faster (max clock rate of 80 MHz compared to 40 MHz), have more peripherals available, offer more program memory (flash) and data memory (RAM), and have significantly more computational horsepower due to the 32-bit address and data buses and single-cycle multiply for 32-bit math.  The primary disadvantages are that they come only in surface mount packages, making them harder to work with for fast prototyping compared to the DIP (dual-inline packages) 8-bit PICs that can be plugged into a breadboard; and they must be powered by 2.3-3.6 V, unlike the 5 V of DIP 8-bit PICs and some DIP chips we would like to interface with.  (Of course surface mount and lower operating voltages are vastly superior for commercial embedded products, and we will find ways to work around the disadvantages mentioned.)
-Particular numbers referenced on this page refer to the [http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en534177 PIC32MX460F512L] chip, which is the PIC32 used on the NU32 board. (You may wish to compare the capabilities of our PIC to others on [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2870 the Microchip PIC32 parametric table].) The NU32 development board is shown at right.  The NU32 board was designed by Andy Long to easily plug into a standard prototyping breadboard (DIP profile), allowing easy prototyping with the PIC32.  The NU32 board also has a voltage regulator, a USB connector, and a few LEDs and switches to allow you to get up and running quickly with only the assembled NU32 board, a USB cable, and a PC with free software downloaded from Microchip, once a "bootloader" is installed on the PIC to allow you to program it from your PC.  See the  [[Getting Started with PIC32 | getting started page]].  The NU32 board was created with inspiration from the [http://www.sparkfun.com/commerce/product_info.php?products_id=8971 UBW32 board].  We wanted a board that was a little bit smaller, so we sacrificed some pins we thought unnecessary for the majority of mechatronics projects.  We also wanted a board that gave students some experience soldering non-surface-mount components.
+Particular numbers referenced on this page refer to the [http://www.microchip.com/wwwproducts/Devices.aspx?dDocName=en534177 PIC32MX460F512L] chip, which is the PIC32 used on the NU32 board. (You may wish to compare the capabilities of our PIC to others on [http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=2870 the Microchip PIC32 parametric table].) The NU32 development board is shown at right.  The NU32 board was designed by Andy Long to easily plug into a standard prototyping breadboard (DIP profile), allowing easy prototyping with the PIC32.  The NU32 board also has a voltage regulator, a USB connector, and a few LEDs and switches to allow you to get up and running quickly with only the assembled NU32 board, a USB cable, and a PC with free software downloaded from Microchip (once a "bootloader" is installed on the PIC to allow you to program it from your PC).  See the  [[Getting Started with PIC32 | getting started page]].  The NU32 board was created with inspiration from the [http://www.sparkfun.com/commerce/product_info.php?products_id=8971 UBW32 board].  We wanted a board that was a little bit smaller, so we sacrificed some pins we thought unnecessary for the majority of mechatronics projects.  We also wanted a board that gave students some experience soldering non-surface-mount components.
 The purpose of this page is to provide a brief overview of PIC32 and NU32 hardware and programming for the beginner.  Microchip provides many reference manuals, data sheets, application notes, and sample software, and there are many other helpful web resources to take you further.

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-Below the different pin functions are briefly summarized.  The most important functions for ME 333 are indicated in '''bold'''.  To learn more about these functions, you can consult the data sheet, but for the most part you will learn how to use these functions by modifying sample programs.  See also the suggestions at the bottom of the page.
+Below the different pin functions are briefly summarized.  The most important functions for ME 333 are indicated in '''bold'''.  To learn more about these functions, you can consult the data sheet, but for the most part you will learn how to use these functions by modifying sample programs.  See also the Further Reading section at the bottom of the page.
 {| border="1"

@@ Line 11: / Line 11: @@
 Our PIC32MX460F512L features a max clock frequency of 80 MHz, 512K program memory (flash), 32K data memory (RAM), multiple interrupt sources and handling routines, 16 analog-to-digital input channels, many digital I/O channels (with outputs that can be configured for open-drain), USB 2.0, two I2C and two SPI synchronous serial communication modules, two UARTs for RS-232 or RS-485 asynchronous serial communication, five 16-bit counter/timers (configurable to give two 32-bit timers), five pulse-width modulation outputs, and a number of pins that can generate interrupts based on external signals, among other features.  This PIC has 100 pins, many (but not all) of which are used or broken out by the NU32 board.
-To cram this much functionality into 100 pins, many of the pins serve multiple functions.  For example, pin 20 can serve as a comparator input, an analog input, a change notification input which can generate an interrupt when the pin changes state, or a digital input or output.  Which function a particular pin serves is determined by "Special Function Registers" (SFRs) that contain configuration bits specifying the desired use of the pin.  Typically your program sets these configuration bits at the beginning of execution, and the functions of the pins are fixed while your program runs.  (It is possible, though rarely needed, to change the configuration bits and change the function of pins during execution.)
+To cram this much functionality into 100 pins, many of the pins serve multiple functions.  For example, pin 20 can serve as a comparator input, an analog input, a change notification input which can generate an interrupt when the pin changes state, or a digital input or output.  Which function a particular pin serves is determined by "Special Function Registers" (SFRs) that contain configuration bits specifying the desired use of the pin.  Typically your program sets these configuration bits at the beginning of execution, and the functions of the pins are fixed while your program runs.  (It is possible, though rarely needed, to change the configuration bits and change the function of pins on the fly.)
 A figure showing the pin-out of the PIC32MX4XX is shown at right.  Shaded pins tolerate up to 5.5 V as inputs, and pins that are "checked" are brought out to the pins of the NU32 board, described below.  Click on the image for higher resolution.

@@ Line 135: / Line 135: @@
 '''NOT RECOMMENDED:'''  If none of the power connections above are available, it is possible to power the board by providing 5V at pins 1 or 58 of the NU32 board.  These pins are are connected to the USB 5V when the power switch is in the USB position, and they are connected to the output of the 5V regulator when the power switch is in the EXT position.  This method should be avoided, to prevent accidental wiring that could damage the PIC.
-'''Note on using the 3.3V and 5V output pins:'''  If the NU32 is powered by a USB cable, typically such a connection can only provide about 500 mA total.  Take this into account when you decide how much current to try to draw from these pins.  Even if the NU32 board is powered by a higher-current supply, such as a battery or a wall-powered adapter brick, keep in mind that the onboard 3.3V regulator can only source approximately 950 mA max.  You should not try to draw more than, say, half that.  Also, if your supply is unregulated and you are using a 5V regulator on the NU32 board, you must take into account its current limit.  Usual rule of thumb:  don't try to drive motors, which often draw hundreds of mA, up to a few amps in typical ME 333 applications, using current flowing through your NU32 board.
+'''Note on using the 3.3V and 5V output pins:'''  If the NU32 is powered by a USB cable, typically such a connection can only provide about 500 mA total.  Take this into account when you decide how much current to try to draw from these pins.  Even if the NU32 board is powered by a higher-current supply, such as a battery or a wall-powered adapter brick, keep in mind that the onboard 3.3V regulator can only source approximately 950 mA max.  You should not try to draw more than, say, half that.  Also, if your supply is unregulated and you are using a 5V regulator on the NU32 board, you must take into account your board's regulator's current limit.  Usual rule of thumb:  don't try to drive motors, which often draw hundreds of mA, up to a few amps in typical ME 333 applications, using current flowing through your NU32 board.
 <br clear=all>

@@ Line 198: / Line 198: @@
 So, to summarize, this was the chain of #include files:
 * The Hello World main.c program included HardwareProfile.h.
-** HardwareProfile.h does little but include Compiler.h and HardwareProfile_NU32.h.
+** HardwareProfile.h does little but include HardwareProfile_NU32.h and Compiler.h.
 *** HardwareProfile_NU32.h defines initialization functions to set 4 pins of Port E as digital outputs and 2 as digital inputs; defines convenient names for these pins; and defines functions for turning the NU32 LEDs on and off.
 *** Compiler.h provides a few definitions and includes some standard C libraries (stdio.h, stdlib.h, string.h) as well as p32xxxx.h and plib.h.

@@ Line 197: / Line 197: @@
 So, to summarize, this was the chain of #include files:
-* The Hello World main.c program included HardwareProfile.h and Compiler.h.
+* The Hello World main.c program included HardwareProfile.h.
-** HardwareProfile.h does little but include HardwareProfile_NU32.h.
+** HardwareProfile.h does little but include Compiler.h and HardwareProfile_NU32.h.
 *** HardwareProfile_NU32.h defines initialization functions to set 4 pins of Port E as digital outputs and 2 as digital inputs; defines convenient names for these pins; and defines functions for turning the NU32 LEDs on and off.
-** Compiler.h provides a few definitions and includes some standard C libraries (stdio.h, stdlib.h, string.h) as well as p32xxxx.h and plib.h.
+*** Compiler.h provides a few definitions and includes some standard C libraries (stdio.h, stdlib.h, string.h) as well as p32xxxx.h and plib.h.
-*** plib.h includes the peripheral libraries (e.g., adc10.h, i2c.h, etc.), which you can learn more about in [[Media:32-bit-Peripheral-Library-Guide.pdf|this peripheral library guide]] (314 page pdf).
+**** plib.h includes the peripheral libraries (e.g., adc10.h, i2c.h, etc.), which you can learn more about in [[Media:32-bit-Peripheral-Library-Guide.pdf|this peripheral library guide]] (314 page pdf).
-*** p32xxxx.h includes p32mx460f512l.h.
+**** p32xxxx.h includes p32mx460f512l.h.
-**** p32mx460f512l.h is a big file and makes many of the microcontroller-specific definitions.  This includes defining data types and variable names for the peripheral SFRs (e.g., LATE, PORTE, and TRISE, as mentioned above) and some convenient names for addresses and interrupt numbers and vectors.  It also includes ppic32mx.h., which defines some other mnemonic variable names.
+***** p32mx460f512l.h is a big file and makes many of the microcontroller-specific definitions.  This includes defining data types and variable names for the peripheral SFRs (e.g., LATE, PORTE, and TRISE, as mentioned above) and some convenient names for addresses and interrupt numbers and vectors.  It also includes ppic32mx.h., which defines some other mnemonic variable names.
 Finally, the bootloader main.c file defined some of the configuration bits for the clock circuitry, to set the SYSCLK and PBCLK to 80 MHz, and the USBCLK to 48 MHz, given that we have an 8 MHz crystal.

@@ Line 172: / Line 172: @@
 # Added the HardwareProfile.h and HardwareProfile_NU32.h to your project. (This allows your project to know it has to recompile if these files are changed.)
 # Added procdefs.ld (a "linker" file) to your project.  This file is '''different''' from the procdefs.ld file used for your bootloader.  These files tell MPLAB where the code should be placed in program memory, and the two procdefs.ld are different so your Hello World program does not overwrite the bootloader code.  (This is not the only linker file used, so we put it under "Other Files.")
-# Added a search path to the "Include Search Path," C:\Microchip Solutions\Microchip\Include and the directory of your project, where you are creating your source code.
+# Added two search paths to "Include Search Path," (1) C:\Microchip Solutions\Microchip\Include and (2) the directory of your project, where you are creating your source code.
 # Created a constant "PIC32_NU32" in the MPLAB PIC32 C Compiler tab.
 # Wrote the main.c code for Hello World, added it to the project, and used Project->Build all to create a .hex file that you then loaded on to the PIC32 using the HID bootloader.

@@ Line 180: / Line 180: @@
 OK, continuing through HardwareProfile_NU32.h, we see that our PIC will have a system frequency of 80 MHz.  '''Note that this does not actually set what the PIC does with the oscillator we have provided.'''
-Continuing with HardwareProfile_NU32.h, we see that a function "mInitAllLEDs()" is defined.  It does two things:  it sets the latch bits (LATE) and the "tri-state" bits (TRISE) of port E.  LATE and TRISE are the values of Special Function Registers (SFRs) for the digital I/O peripherals and are defined elsewhere, as we will see soon. (See also [[PIC32MX: Digital Inputs]] and [[PIC32MX: Digital Outputs]] for more on using the digital I/O peripherals.)  The command "LATE |= 0x000F" logically "ORs" the current bits of LATE with the bits of the hexadecimal value 0x000F.  (This is equivalent to the command "LATE = LATE | 0x000F", and C programmers will notice that this syntax is similar to the syntax a += 3, which is equivalent to a = a + 3.)  Note that 0x000F corresponds to a binary value of 0000 0000 0000 1111.  So whatever the current values of LATE are, the last four bits (least significant bits) will be 1 after this operation.  (Note that 0x000F has only 16 bits, but LATE is technically 32-bit.  The first 16-bits are not used, however; see Section 12 of the [[Media:61132B_PIC32ReferenceManual.pdf|PIC32 Reference Manual]]).  The command "TRISE &= 0xFFF0" sets whether the pins in port E will be inputs or outputs by doing a binary AND with 1111 1111 1111 0000.  In other words, the first 12 bits will be unchanged, while the last four bits will be set to outputs (0 = output, 1 = input).  These last four bits are going to be used to power our NU32 board LEDs, so they must be outputs.  We then see the mnemonic names "mLED_x" given to the (output) values of these four bits.  A number of functions are then defined to get the current values of the LEDs and to turn the LEDs on, turn them off, or toggle them.  (Note that an output value of 0, or 0 voltage, corresponds to the LED being on; consult the NU32 schematic to see why this is the case.)  Finally, functions are defined that will configure bits 4 and 5 of port E as inputs.  These are used for the USER and PRG switches on the NU32 board.  The constants swProgram and swUser return the current values of these inputs, 0 for low (ground), 1 for high (3.3V).
+Continuing with HardwareProfile_NU32.h, we see that a function "mInitAllLEDs()" is defined.  It does two things:  it sets the latch bits (LATE) and the "tri-state" bits (TRISE) of port E.  LATE and TRISE are the values of Special Function Registers (SFRs) for the digital I/O peripherals and are defined elsewhere, as we will see soon. (See also [[PIC32MX: Digital Inputs]] and [[PIC32MX: Digital Outputs]] for more on using the digital I/O peripherals.)  The command "LATE |= 0x000F" bitwise logically "ORs" the current bits of LATE with the bits of the hexadecimal value 0x000F.  (This is equivalent to the command "LATE = LATE | 0x000F", and C programmers will notice that this syntax is similar to the syntax a += 3, which is equivalent to a = a + 3.)  Note that 0x000F corresponds to a binary value of 0000 0000 0000 1111.  So whatever the current values of LATE are, the last four bits (least significant bits) will be 1 after this operation.  (Note that 0x000F has only 16 bits, but LATE is technically 32-bit.  The first 16-bits are not used, however; see Section 12 of the [[Media:61132B_PIC32ReferenceManual.pdf|PIC32 Reference Manual]]).  The command "TRISE &= 0xFFF0" sets whether the pins in port E will be inputs or outputs by doing a bitwise AND with 1111 1111 1111 0000.  In other words, the first 12 bits will be unchanged, while the last four bits will be set to outputs (0 = output, 1 = input).  These last four bits are going to be used to power our NU32 board LEDs, so they must be outputs.  We then see the mnemonic names "mLED_x" given to the (output) values of these four bits.  A number of functions are then defined to get the current values of the LEDs and to turn the LEDs on, turn them off, or toggle them.  (Note that an output value of 0, or 0 voltage, corresponds to the LED being on; consult the NU32 schematic to see why this is the case.)  Finally, functions are defined that will configure bits 4 and 5 of port E as inputs.  These are used for the USER and PRG switches on the NU32 board.  The constants swProgram and swUser return the current values of these inputs, 0 for low (ground), 1 for high (3.3V).
 OK, now let's open Compiler.h from a few paragraphs earlier.  We find that since we are using the C32 compiler, it includes the header files p32xxxx.h and plib.h.  We will take a look at those shortly, but let's continue with Compiler.h.  It also includes some standard C libraries, like stdio.h (libraries for input and output), stdlib.h, and string.h (for string manipulation).  It makes a few more definitions which are beyond our scope for now.  You might be interested to see the defined function "Nop()" which stands for "no operation," i.e., just waste a cycle.  It is defined using an assembly code command using asm("nop").  In other words, if you were coding in assembly (and thank goodness you're not), you would type "nop."  You can write low-level assembly code in C using the command asm().  If you are interested, you can always see the assembly code generated by your C code by using View->Disassembly Listing in the MPLAB IDE.