Hello friends! As you can guess for the title, I've made a custom board with this chip and I've tried everything to make run a blink on this chip with no success. Following I write some key points:
- I have my own boards definition for Arduino, so I'm familiar with variants, boards.txt, and so on. I also have compiled UF2 bootloaders for each board.
- I have experienced same problems with ATSAMD51J18A, so it must be software related issue with "no previously arduino supported" chips.
- This same custom boards works fine with ATSAMD51J20A, so it's not the board itself.
- I've modified CMSIS-Atmel to include D21J15A. The chip was indeed already there, but not added in the "include" list, so no huge modification or scratch coding.
- The debugger says me that the chip is running "cortex debug handler" what it seems to be a place to go when the stack overflows or something like this, so this is maybe a clue.
- I use JLINK Mini for program and debug.
- I don't want to run a bootloader, just the program .bin itself placed on 0X0 memory. But anyway I also tried with it but no results. With D51J20A I just loaded the program on 0x0 and just for the first time after loading I had to connect debugging for make it run.
This is my board.txt definition of the board:
# -----------------------------------
# Remote IO (SAMD21)
# -----------------------------------
remote_io_d21.name=Remote IO (SAMD21)
# VID/PID for Bootloader, Arduino
remote_io_d21.vid.0=0x010A
remote_io_d21.pid.0=0x0001
# Upload
remote_io_d21.upload.tool=bossac18
remote_io_d21.upload.protocol=sam-ba
remote_io_d21.upload.maximum_size=32768
remote_io_d21.upload.maximum_data_size=4096
remote_io_d21.upload.offset=0x0000
remote_io_d21.upload.use_1200bps_touch=true
remote_io_d21.upload.wait_for_upload_port=true
remote_io_d21.upload.native_usb=true
# Build
remote_io_d21.build.mcu=cortex-m0plus
remote_io_d21.build.chip=SAMD21J15A
remote_io_d21.build.f_cpu=48000000L
remote_io_d21.build.usb_product="Remote IO (SAMD21)"
remote_io_d21.build.usb_manufacturer="Navarro Systems"
remote_io_d21.build.board=RID21_BOARD
remote_io_d21.build.core=arduino
remote_io_d21.build.extra_flags=-D__SAMD21J15A__ -DARM_MATH_CM0PLUS {build.usb_flags}
remote_io_d21.build.ldscript=linker_scripts/gcc/flash_without_bootloader.ld
remote_io_d21.build.openocdscript=scripts/openocd/daplink_samd21.cfg
remote_io_d21.build.variant=remote_io_d21
remote_io_d21.build.variant_system_lib=
remote_io_d21.build.vid=0x010A
remote_io_d21.build.pid=0x0001
remote_io_d21.bootloader.tool=jlink
remote_io_d21.bootloader.file=remote_io_d21/bootloader-remote_io_d21.bin
# Menu: Board Version
remote_io_d21.menu.board_version.1_0=V2.1
remote_io_d21.menu.board_version.1_0=V2.0
remote_io_d21.menu.board_version.1_0=V1.0
# Menu: Optimization
remote_io_d21.menu.opt.small=Small (-Os) (standard)
remote_io_d21.menu.opt.small.build.flags.optimize=-Os
remote_io_d21.menu.opt.fast=Fast (-O2)
remote_io_d21.menu.opt.fast.build.flags.optimize=-O2
remote_io_d21.menu.opt.faster=Faster (-O3)
remote_io_d21.menu.opt.faster.build.flags.optimize=-O3
remote_io_d21.menu.opt.fastest=Fastest (-Ofast)
remote_io_d21.menu.opt.fastest.build.flags.optimize=-Ofast
remote_io_d21.menu.opt.dragons=Here be dragons (-Ofast -funroll-loops)
remote_io_d21.menu.opt.dragons.build.flags.optimize=-Ofast -funroll-loops
# Menu: USB Stack
remote_io_d21.menu.usbstack.arduino=Arduino
remote_io_d21.menu.usbstack.tinyusb=TinyUSB
remote_io_d21.menu.usbstack.tinyusb.build.flags.usbstack=-DUSE_TINYUSB
# Menu: Debug
remote_io_d21.menu.debug.off=Off
remote_io_d21.menu.debug.on=On
remote_io_d21.menu.debug.on.build.flags.debug=-g
This is my linker script of the board:
/*
Copyright (c) 2014-2015 Arduino LLC. All right reserved.
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
See the GNU Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
/* Linker script to configure memory regions.
* Need modifying for a specific board.
* FLASH.ORIGIN: starting address of flash
* FLASH.LENGTH: length of flash
* RAM.ORIGIN: starting address of RAM bank 0
* RAM.LENGTH: length of RAM bank 0
*/
MEMORY
{
FLASH (rx) : ORIGIN = 0x00000000, LENGTH = 0x00008000
RAM (rwx) : ORIGIN = 0x20000000, LENGTH = 0x00001000
}
/* Linker script to place sections and symbol values. Should be used together
* with other linker script that defines memory regions FLASH and RAM.
* It references following symbols, which must be defined in code:
* Reset_Handler : Entry of reset handler
*
* It defines following symbols, which code can use without definition:
* __exidx_start
* __exidx_end
* __copy_table_start__
* __copy_table_end__
* __zero_table_start__
* __zero_table_end__
* __etext
* __data_start__
* __preinit_array_start
* __preinit_array_end
* __init_array_start
* __init_array_end
* __fini_array_start
* __fini_array_end
* __data_end__
* __bss_start__
* __bss_end__
* __end__
* end
* __HeapLimit
* __StackLimit
* __StackTop
* __stack
* __ram_end__
*/
ENTRY(Reset_Handler)
SECTIONS
{
.text :
{
__text_start__ = .;
KEEP(*(.isr_vector))
*(.text*)
KEEP(*(.init))
KEEP(*(.fini))
/* .ctors */
*crtbegin.o(.ctors)
*crtbegin?.o(.ctors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .ctors)
*(SORT(.ctors.*))
*(.ctors)
/* .dtors */
*crtbegin.o(.dtors)
*crtbegin?.o(.dtors)
*(EXCLUDE_FILE(*crtend?.o *crtend.o) .dtors)
*(SORT(.dtors.*))
*(.dtors)
*(.rodata*)
KEEP(*(.eh_frame*))
} > FLASH
.ARM.extab :
{
*(.ARM.extab* .gnu.linkonce.armextab.*)
} > FLASH
__exidx_start = .;
.ARM.exidx :
{
*(.ARM.exidx* .gnu.linkonce.armexidx.*)
} > FLASH
__exidx_end = .;
/* To copy multiple ROM to RAM sections,
* uncomment .copy.table section and,
* define __STARTUP_COPY_MULTIPLE in startup_ARMCMx.S */
/*
.copy.table :
{
. = ALIGN(4);
__copy_table_start__ = .;
LONG (__etext)
LONG (__data_start__)
LONG (__data_end__ - __data_start__)
LONG (__etext2)
LONG (__data2_start__)
LONG (__data2_end__ - __data2_start__)
__copy_table_end__ = .;
} > FLASH
*/
/* To clear multiple BSS sections,
* uncomment .zero.table section and,
* define __STARTUP_CLEAR_BSS_MULTIPLE in startup_ARMCMx.S */
/*
.zero.table :
{
. = ALIGN(4);
__zero_table_start__ = .;
LONG (__bss_start__)
LONG (__bss_end__ - __bss_start__)
LONG (__bss2_start__)
LONG (__bss2_end__ - __bss2_start__)
__zero_table_end__ = .;
} > FLASH
*/
__etext = .;
.data : AT (__etext)
{
__data_start__ = .;
*(vtable)
*(.data*)
. = ALIGN(4);
/* preinit data */
PROVIDE_HIDDEN (__preinit_array_start = .);
KEEP(*(.preinit_array))
PROVIDE_HIDDEN (__preinit_array_end = .);
. = ALIGN(4);
/* init data */
PROVIDE_HIDDEN (__init_array_start = .);
KEEP(*(SORT(.init_array.*)))
KEEP(*(.init_array))
PROVIDE_HIDDEN (__init_array_end = .);
. = ALIGN(4);
/* finit data */
PROVIDE_HIDDEN (__fini_array_start = .);
KEEP(*(SORT(.fini_array.*)))
KEEP(*(.fini_array))
PROVIDE_HIDDEN (__fini_array_end = .);
KEEP(*(.jcr*))
. = ALIGN(16);
/* All data end */
__data_end__ = .;
} > RAM
.bss :
{
. = ALIGN(4);
__bss_start__ = .;
*(.bss*)
*(COMMON)
. = ALIGN(4);
__bss_end__ = .;
} > RAM
.heap (COPY):
{
__end__ = .;
PROVIDE(end = .);
*(.heap*)
__HeapLimit = .;
} > RAM
/* .stack_dummy section doesn't contains any symbols. It is only
* used for linker to calculate size of stack sections, and assign
* values to stack symbols later */
.stack_dummy (COPY):
{
*(.stack*)
} > RAM
/* Set stack top to end of RAM, and stack limit move down by
* size of stack_dummy section */
__StackTop = ORIGIN(RAM) + LENGTH(RAM) ;
__StackLimit = __StackTop - SIZEOF(.stack_dummy);
PROVIDE(__stack = __StackTop);
__ram_end__ = ORIGIN(RAM) + LENGTH(RAM) -1 ;
/* Check if data + heap + stack exceeds RAM limit */
ASSERT(__StackLimit >= __HeapLimit, "region RAM overflowed with stack")
}
The rest of the code is the same that ATSAMD21G18 on Adafruit boards.
I've already read the following post with no results for me:
How to write programs for a custom SAMD21 board using Arduino IDE
ATSAMD21G17D processor programming?
@MartinL posts have been a great help, buy anyway I couldn't make it run... 
Thanks in advance for everyone that could help!