SAMD21 Custom Board Trouble with Bootloader Modifications to Load over UART

Other Hardware 3rd Party Boards
1

I can't seem to figure out what I'm doing wrong here. I have a custom SAMD21 board. I tried to modify the standard samd21_sam_ba.hex bootloader to match my board. I have modified the board_definitions_boardID.h file to change the pins to what I am using. So far I have modified the LED pins and that part worked. I can still upload via USB using the command:

...\AppData\Local\Arduino15\packages\arduino\tools\bossac\1.7.0/bossac.exe -i -d --port=COM81 -U true -i -e -w -v ...\Documents\Arduino\ProgrammingScripts\AT_8.ino.at_board5.bin -R

But if I try to do upload over UART with a USB-UART converter using the same command, I get:

Set binary mode
Send auto-baud
Set binary mode
No device found on COMXX

I use PA17 for my RX pin, and PA16 for my TX pin. This works fine in the application. It is set up on SERCOM1 with PA17 being pad 1 and PA16 pad 0. In my board_definition file I have this defined as follows:

#define BOOT_USART_MODULE SERCOM1
#define BOOT_USART_BUS_CLOCK_INDEX PM_APBCMASK_SERCOM1
#define BOOT_USART_PER_CLOCK_INDEX GCLK_CLKCTRL_ID_SERCOM1_CORE_Val
#define BOOT_USART_PAD_SETTINGS UART_RX_PAD1_TX_PAD0
#define BOOT_USART_PAD3 PINMUX_UNUSED
#define BOOT_USART_PAD2 PINMUX_UNUSED
#define BOOT_USART_PAD1 PINMUX_PA17C_SERCOM1_PAD1
#define BOOT_USART_PAD0 PINMUX_PA16C_SERCOM1_PAD0

I believe these settings are correct, but I can't figure out the issue. I believe I am building the bootloader correctly because the LEDs have changed and I can still program via USB. Any help would be very much appreciated because I'm running out of ideas.

2

I'm no expert with SAMD21. I think you have to compile the bootloader with the options you want.

which looks like an Atmel Studio project at a glance but the readme says you can get the toolchain and run the Makefile. I would like to know how it goes (e.g. post the build text please), I have been wanting to do a SAMD21 (or maybe 51) board for a while, unfortunately, have not really done anything.

Also, do you have a way to upload the bootloader?

3

Hi jamesod,

Have you double tapped the reset button before uploading?

To use the SAMD21's bootloader UART, it's necessary to put the processor into bootloader mode first.

4

So, I slept on it, and I figured out the issue. I was powering the board through USB, and apparently the UART bootloader does not work if USB is plugged in.

5

Ron

I started with these instructions here: Compile | Compiling ATSAMD21 Bootloader | Adafruit Learning System

For this I had to modify the board_definitions.h file to add a case for my board, and I added a board_definitions_myboard.h file that I modified from the board_definitions_genuino_zero.h file that is given in the ArduinoCore-samd.

I also modified the makefile. The ReadMe is a little out of date. Its 2 years old, but the makefile is a month old, so the instructions don't match perfectly.

Assuming you have the Arduino IDE and the SAMD21 toolchain installed in the default locations, you only have to modify the BOARD_ID?= and NAME?= lines of the makefile.

6

Next challenge is a bootloader for my other board. That one will have to boot from USB or spi flash. I expect that to be more of a challenge, but I'm looking at this example to start:

7

jamesod:
Assuming you have the Arduino IDE and the SAMD21 toolchain installed in the default locations, you only have to modify the BOARD_ID?= and NAME?= lines of the makefile.

Hi sorry for digging up this thread, but maybe you can help me. I am trying to compile a custom bootloader and have done what you have posted here, ie create a board definition, include it in board_definitions.h, and mod the Makefile. I call make from the command prompt of Cygwin64. It compiles up to where something #includes <sam.h> then it throws an error... board_driver_i2c.h:23:17: fatal error: sam.h: No such file or directory

I have latest SAMD package 1.6.20 installed on IDE 1.8.8

How did you get arround this?

Thx

8

Problem solved. I was trying to make a boolader form the Sparkfun Dev board package, which is out of date. When I tried it from the Zero package it worked.