Minimal code for PIC32

A minimal source code to start working with pic32mz, without the use of any library (no Harmony).

toolchain

• install mplab xc32 version less than or equaul to 2.15 (<= v2.15) and add xc32 bin directory it to PATH
• install make and add it to PATH
• install Git
• if python tools are used install python 3 and add it to PATH

IMPORTANT NOTE FOR LINUX x64 MACHINE

• on linux before installing xc32 you must install dependencies (lib32) to be able to install it, otherwise it won't work.

# For Ubuntu
sudo apt-get install libc6:i386 libx11-6:i386 libxext6:i386 libstdc++6:i386 libexpat1:i386

# For Fedora
sudo dnf install libX11.i686 libXext.i686 libgcc.i686 libstdc++.i686 expat.i686

• For more infos go to https://microchipdeveloper.com/install:mplabx-lin64

configuration

Before start, make sure to adjust the pic32_config.h header file.

GPIO

• pic32mz pin count, will automatically ignore non-exsistant gpio ports
• set the initial state of gpios, as input or output. this inital config is applied if gpio_init is called, otherwise all pins can be set input or output in run time using gpio_input_set and gpio_output_set
• pins used for functions, such as UART are adjusted automatically in uart_init

TIMERS

• pic32mz have 9 timers, timer1 being different from the 8 other timers, it has its own init func
• timer 1 is used to generate the tick, therefore cannot be disabled from config header.
• enabling a timer will automatically enable its interrupt

UARTs

• picmz have 6 UARTS, and the mapping for uart pins rx and tx should be chosed from the datasheet because only a set of pins can be used for rx or tx for any specifig UART
• enabling a UART will make it available for use
• PIC32_UART_x_RX_PIN and PIC32_UART_x_RX_PIN should be set for any enabled UART

INTERRUPT PRIORITY

priorities for peripherals are set in the config file, thus, they are set in compile time.

the reason is, for better performance pic32mz uses a set of Shadow Registers to save the context of the CPU during interrupts. Each shadow register is related to an interrupt priority. for example interrupts with priority 5, will use shadow register 5 to save their context. setting the Shadow register for a given interrupt vector is set in compile time in the definition of the isr by the iplxAUTO keyword.

application

by default tha main function calls two functions, app_init one time before the infinite loop and app_task() in an infinite loop

app.c provide a simple example of use.

building

the build is done by calling make, preferably call make clean before.

Makefile

there are several variables to addapt to the MCU used or the way how to program

MCU : set the name of the mcu used LD_SCRIPT : takes either custom to use a customed linker script, in case there is a bootloader in the board or set it to nothing to use the default linker script from the compiler.

CSRCS : if any source file is added to the project, the source file should be added in the list

programming

if the default linker script from the compiler is used, the programing is done with a pickit

if the custom liker script is used, a booloader should be burned in the MCU to be able to upload code using UART or UDP

there are examples of bootloader from the harmony library.

if a bootloader is in place, the script in tools/programmer.py can be used to upload the code through UART or UDP.