Difference between revisions of "NU32v2: Starting a New Project and Putting it on the NU32v2"
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'''**THIS PAGE IS UNDER CONSTRUCTION AND IS NOT COMPLETE**''' |
'''**THIS PAGE IS UNDER CONSTRUCTION AND IS NOT COMPLETE**''' |
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'''**NDM |
'''**NDM 1/13/2011**''' |
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= PIC32 Programming in C = |
= PIC32 Programming in C = |
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'''Note: Code downloaded from Microchip is constantly evolving, and it is possible that the information below will be outdated for future code releases. This information is accurate for code downloaded from Microchip's website in |
'''Note: Code downloaded from Microchip is constantly evolving, and it is possible that the information below will be outdated for future code releases. This information is accurate for code downloaded from Microchip's website in January 2011. Also, sample code developed by us and others are generally modified from working code for different purposes, and therefore you may find unnecessary legacy code, programming inefficiency, or even incorrect code in some samples.''' |
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You should complete the |
You should complete the instructions in [[NU32v2: Software to Install]] if you have not already. For this page specifically, you need to |
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* download and install the MPLAB IDE (Integrated Development Environment) that you use for programming, compiling, debugging, and simulating your PIC code |
* download and install the MPLAB IDE (Integrated Development Environment) that you use for programming, compiling, debugging, and simulating your PIC code. The MPLAB C Compiler for PIC32 is included in the "complete" installation of the IDE |
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* download |
* download the Serial Bootloader for NU32v2 PC application |
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* download the Microchip Applications Library |
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* install a "bootloader" on your PIC32 |
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* create a "Hello World" program for the NU32 that you compile to a .hex file, download to your PIC32, and run. |
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The remainder of this page describes how to create a new Project in MPLAB, compile a general "Hello World" program to blink the LEDs on the NU32v2, and use the Serial Bootloader of NU32v2 PC application to put the program on the NU32v2. |
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The bootloader is programmed to the PIC's flash memory using a programmer (such as Microchip's ICD). Once the bootloader is there, you should never have to use a programmer again (unless you accidentally overwrite the bootloader in flash memory by using the wrong procdefs.ld "linker" file). From that point on, you should be able to program your PIC simply using a USB cable to connect your PC to the NU32 board. |
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= Create a New Project in MPLAB for the NU32v2 = |
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After you've installed all the software on your PC, you should have the following directories: |
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* C:\Microchip Solutions: This has a lot of demo code, among other things. The C:\Microchip Solutions\Microchip\Include directory contains .h files that you are likely to need for your programs. Also, C:\Microchip Solutions\USB Device - Bootloaders\HID - Bootloader has .hex bootloaders for different PICs. '''(Note: these .hex bootloaders don't work with the NU32 board, which is why we compiled our own bootloader.)''' It also has PC source software for USB communication with a PIC with the bootloader installed (for programming the PIC without a programmer device). |
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* C:\Program Files\Microchip: There is a '''lot''' of stuff under this directory. Two notable directories are MPLAB C32 and MPLAB C32 Suite. These directories look essentially exactly the same, unless I'm missing something. One directory of interest is C:\Program Files\Microchip\MPLAB C32\pic32_libs\include, which has plib.h (function definitions for the peripheral libraries) and subdirectories peripheral (with .h files for peripheral libraries) and proc (with .h files for different PICs containing type definitions and memory addresses specific to the PICs). Another directory of interest is C:\Program Files\Microchip\MPLAB C32\pic32_libs\peripheral, which has directories for each of the peripherals and .c, .inc, and .h source files for the libraries for these peripherals. |
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= "Hello World" example code for NU32v2 = |
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In addition, you have the HID Bootloader program in your PC's start menu. |
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When you created your first Hello World project, you went through the following steps: |
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= Using the Serial Bootloader for NU32v2 PC Application = |
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# Created a new directory to hold the project, and put the files "HardwareProfile.h" and "HardwareProfile_NU32.h" "header" files into the directory. |
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# Used the Project Wizard to create a new project in that directory and specified that you would be using the PIC32MX460F512L microcontroller. |
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# 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.) |
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# 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.") |
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# 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. |
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# Created a constant "PIC32_NU32" in the MPLAB PIC32 C Compiler tab. |
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# 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. |
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So what was the purpose of each of these steps? '''Steps 2 and 6''' defined constants that tell the compiler the microcontroller you are using and the board it is being used on. How are these constants used? Open up HardwareProfile.h, which you included in your project ('''step 3'''). Because you have defined __32MX460F512L__ ('''step 2'''), and because you have defined PIC32_NU32 ('''step 6'''), this file includes "HardwareProfile_NU32.h". Now take a look at the file HardwareProfile_NU32.h. The first thing it does is include "Compiler.h". We can find Compiler.h in C:\Microchip Solutions\Microchip\Include, which we included in our "Include Search Path" ('''step 5''') so the compiler would know where to find it. Let's come back to Compiler.h shortly. |
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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.''' |
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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). |
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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. |
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Let's go back and look at p32xxxx.h and plib.h, referenced by Compiler.h. They can be found under C:\Program Files\Microchip\MPLAB C32\pic32_libs\include. plib.h simply includes a bunch of .h files for the peripheral libraries: 10-bit ADC (adc10.h) which further makes use of definitions in ports.h; I2C serial communication (i2c.h); etc. All of these .h files are under C:\Program Files\Microchip\MPLAB C32\pic32_libs\include\peripheral. We can open one of these many .h files, and we'll see that they define functions that are designed to simplify our use of the peripheral. You can learn more about the use of these peripheral libraries in the [[Media:32-bit-Peripheral-Library-Guide.pdf|peripheral library guide]] (see also Further Reading at the end of this page). Also, you can see the source code for the peripherals to see how the higher-level peripheral functions are created from low-level functions by looking in C:\Program Files\Microchip\MPLAB C32\pic32_libs\peripheral. |
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If we now open p32xxxx.h, we find that it simply includes the file p32mx460f512l.h, which is under C:\Program Files\Microchip\MPLAB C32\pic32_libs\include\proc. If we open up this file... whoa! Finally we see where a lot of the data types and variables and constants are defined that have been used earlier. The details are well beyond our scope here, but we can look at the beginning of the file, where the variable WDTCON (WatchDog Timer CONfiguration) is defined as an unsigned integer (a 32-bit integer from 0 to 2^31-1). Also, the data type __WDTCONbits_t is defined, consisting of a set of structures, and then the variable WDTCONbits is defined of type __WDTCONbits_t. The rest of this very large file defines data types and variables for configuration bits, various constants, quantities associated with interrupts, addresses for peripherals specific to the particular PIC, etc. |
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OK, we've spent a lot of time tracing #include files to see where various things are defined, configuration bits set, etc. We could spend more time on this, but you get the idea. In the MPLAB IDE, you can click on Configure->Configuration Bits to set some of the Configuration Bits using the IDE, rather than in your source files. I think it is best to have it written in your source files so another programmer knows where to find them. So leave the checkbox "Configuration Bits set in code" checked. |
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One more thing that we have not yet mentioned: when you put the bootloader on your PIC, it configured some of the Special Function Registers (SFRs) of your PIC. In particular, open main.c of your bootloader project, and you will see a series of #pragma directives that get executed upon recognizing that you have defined the constant PIC32_NU32. (#pragma directives are compiler-specific instructions, in this case for PIC microcotnrollers, not general C language instructions.) Notice, for example, that FPLLMUL is set to MUL_20 ('''where is this defined?'''), meaning that the PLL (phase-locked loop) in the PIC multiplies the external crystal frequency by 20 (8 MHz x 20 = 160 MHz), and then FPLLIDIV (PLL input divider) divides the frequency by 2, and FPLLODIV (PLL output divider) divides by 1, giving our final system clock of 80 MHz. This is where the actual hardware is configured to give us our actual clock frequency. The peripheral clock is set to the same frequency. USB communication requires a precise 48 MHz clock, and the USB PLL multiplies its input frequency by 12. Therefore, we must provide the USB PLL with a 4 MHz signal, and therefore the bootloader sets UPLLIDIV (USB PLL Input Divider) to 2, to divide the 8 MHz clock by 2. Much of the rest of main.c is devoted to code that allows you to program the PIC by USB communication. |
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OK, going back to the main.c file you created for your Hello World project. After all the includes, a constant SYS_FREQ is defined to be 80 million. '''(NOTE: You could accidentally type 8 million or 800 million, and nothing would work properly! Make sure you type 80 million. Ideally, this SYS_FREQ would be derived from the definitions in the bootloader's main.c file, so you wouldn't have to type again.)''' Then SYSTEMConfigPerformance(SYS_FREQ) is called. This function is defined in C:\Program Files\Microchip\MPLAB C32\pic32_libs\include\peripheral, and one of its purposes is to define some timing constants to hopefully optimize the performance of your PIC (e.g., the use of the pre-fetch cache). Then the LED functions defined in HardwareProfile_NU32.h are used to initialize the LEDs and turn them on or off according to whether the USER button is pushed. |
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Finally, what happens when you "Build All" ('''step 7''')? The compiler compiles any of the individual source files that have been modified since the last Build into .o files, called object code. The linker then puts everything together using a default linker file as well as your procdefs.ld ('''step 4''') and assigns the code to specific addresses in program memory. |
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So, to summarize, this was the chain of #include files: |
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* The Hello World main.c program included HardwareProfile.h. |
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** HardwareProfile.h does little but include HardwareProfile_NU32.h and Compiler.h. |
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*** 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. |
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*** 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. |
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**** 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). |
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**** p32xxxx.h includes p32mx460f512l.h. |
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***** 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. |
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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. |
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Revision as of 16:30, 13 January 2011
**THIS PAGE IS UNDER CONSTRUCTION AND IS NOT COMPLETE**
**NDM 1/13/2011**
PIC32 Programming in C
Note: Code downloaded from Microchip is constantly evolving, and it is possible that the information below will be outdated for future code releases. This information is accurate for code downloaded from Microchip's website in January 2011. Also, sample code developed by us and others are generally modified from working code for different purposes, and therefore you may find unnecessary legacy code, programming inefficiency, or even incorrect code in some samples.
You should complete the instructions in NU32v2: Software to Install if you have not already. For this page specifically, you need to
- download and install the MPLAB IDE (Integrated Development Environment) that you use for programming, compiling, debugging, and simulating your PIC code. The MPLAB C Compiler for PIC32 is included in the "complete" installation of the IDE
- download the Serial Bootloader for NU32v2 PC application
The remainder of this page describes how to create a new Project in MPLAB, compile a general "Hello World" program to blink the LEDs on the NU32v2, and use the Serial Bootloader of NU32v2 PC application to put the program on the NU32v2.
Create a New Project in MPLAB for the NU32v2
"Hello World" example code for NU32v2
Using the Serial Bootloader for NU32v2 PC Application
PIC32 Programming in C with the MPLAB X Beta IDE
Open 'MPLAB X IDE beta'. You will see the following screen.
Click Create New Project.
In Categories, select the Microchip Embedded folder. In Projects, select C/ASM Standalone Project. Click Next >.
In Family, select PIC32, and in Device, select PIC32MX795F512L.
In Select Tool, select PICkit3 if you are going to program the code onto your NU32v2, or select Simulator if you are going to practice coding on your computer.
In Select Compiler, select C32.
In Select Project Name and Folder, create a name for your project, select a location to save it to, ab
