Getting started with SAM-BA on PIC32CXMT devices

Connecting to the SAM-BA monitor

RS-232 UART

For RS-232 UART connection, the serial port on the host running sam-ba used to connect to the PIC32CXMT board design must be plugged to its FLEXCOM0 USART ioset 1 pins.

The name of this serial port may be provided on the command line if needed.

For instance, in the case of the COM9 serial port under Windows:

$ sam-ba -p serial:COM9 -d pic32cxmt -m version
Opening serial port 'COM9'
Connection opened.
ROM Version: v1.0 Jul  4 2019 11:58:23
Connection closed.

Or for /dev/ttyUSB0 when using a FTDI USB/RS-232 adaptor under Linux:

$ sam-ba -p serial:ttyUSB0 -d pic32cxmt -m version
Opening serial port 'ttyUSB0'
Connection opened.
ROM Version: v1.0 Jul  4 2019 11:58:23
Connection closed.

JTAG port

Early Adopter Samples (EAS) suffer from a limitation. Indeed, at power-on or reset, the JTAG access is discarded and must be granted by first disabling the write protection of SFR registers then disabling the JTAG software lock.

#!/bin/bash

SFR_WPMR=0x400504E4
SFR_WPMR_VALUE=0x53465200

SFR_JTAG=0x40050490
SFR_JTAG_VALUE=0

SAMBA="sam-ba -p serial -d pic32cxmt"

$SAMBA -m write32:$SFR_WPMR:$SFR_WPMR_VALUE -m write32:$SFR_JTAG:$SFR_JTAG_VALUE

Supported applets

The list of supported applets can be displayed with the following command:

$ sam-ba -p serial -d pic32cxmt -a help
Known applets: internalflash

Programming the internal flash

In the following example, we program the boot.bin program into the internal flash of the PIC32CXMT device:

$ sam-ba -p serial -d pic32cxmt -a internalflash -c erase:0:0x1000 -c write:boot.bin
$ sam-ba -p serial -d pic32cxmt -a internalflash -c verify:boot.bin

For products with a second bank (SEFC1), the bank (or flash controller instance) is selected by optional parameter of the internalflash applet:

$ sam-ba -p serial -d pic32cxmt -a internalflash:help
Syntax: internalflash:[<instance>]
Parameters:
    instance   Flash controller instance
Examples:
    internalflash      use default board settings
    internalflash:1    select Flash Controller 1 (SEFC1)

When no default board settings exist, the default flash controller is SEFC0.

Getting/Setting the GPNVM bits

Some GPNVM bits, like System Boot Selection bit-field, are used to select the boot mode of the PIC32CXMT device or to enable some of its hardware protections.

Therefore, the internalflash applet also provides means to get/set those GPNVM bits.

For instance, once the a valid application has been programmed into the internal flash, the System Boot Selection (SBS) can be set to 0011b in order to select the standard boot mode on the next power-on or reset:

$ sam-ba -p serial -d pic32cxmt -a internalflash -c setgpnvm:STANDARD_BOOT:SBS_MASK -c getgpnvm
Opening serial port 'ttyUSB0'
Connection opened.
Detected memory size is 1048576 bytes.
Page size is 512 bytes.
Buffer is 59904 bytes (117 pages) at address 0x20000f90.
Supported erase block sizes: 4KB, 8KB, 16KB, 32KB
Executing command 'setgpnvm:STANDARD_BOOT:SBS_MASK'
Executing command 'getgpnvm'
GPNVM = 0x00000060 / STANDARD_BOOT
Connection closed.