SAMD21 Programming Notes

Explorations into how to program SAMD21 chips like those in Trinket M0, Arduino Zero, etc.

How to program a SAMD21 (or other ARM chip really) using a variety of methods, in order to burn a UF2 bootloader or my own programs.

Ways to program a SAMD21 board: (e.g. Trinket M0, QTPy M0, etc)

Reprogram bootloader using UF2
Program with Arduino sketches using uf2
Talk to chip w/ GDB using JTAG/SWD programmer (OpenOCD / JLink via commandline, no Atmel Studio)
Reprogram bootloader with JTAG/WWD programmer (OpenOCD / JLink via commandline, no Atmel Studio)
Program chip with Arduino sketch using JTAG/SWD programmer

Progress so far...

Reprogram bootloader via UF2 - Trinket M0

Double-click button on Trinket M0 to get into UF2 bootloader
- LED will heartbeat
- Trinket M0 shows up as "TRINKETBOOT" disk

Create new UF2 bootloader

git clone https://github.com/Microsoft/uf2-samd21/
cd uf2-samd21
make BOARD=trinket

Copy resulting file update-bootloader.uf2 to disk
Tada, new bootloader installed
Edit file boards/trinket/board_config.h to change bootloader id strings

Program Arduino sketch with UF2 - Trinket M0

Create sketch as normal
Open build tmp directory and copy out .bin file
Use uf2-samd21 'bin2uf2.js' script (from 'scripts' in uf2-samd21 repo) to convert to uf2:
```
node uf2-samd21/scripts/bin2uf2.js sketch_nov24a.ino.bin sketch_nov24a.uf2
```
Copy uf2 file to TRINKETBOOT and tada programmed!
TODO: Look into what bin2uf2 is doing

Connecting Jlink JTAG/SWD to Trinket M0

Solder pads to SWD & SWC pins on back of Trinket M0

Connect following pins from JLink to Trinket M0:

| black | Jlink Gnd   | Trinket M0 Gnd pin |
| red   | Jlink VTref | Trinket M0 3v3 pin |
| green | Jlink SWDIO | Trinket M0 SWD solder pad |
| blue  | Jlink SWCLK | Trinket M0 SWC solder pad |

Power Trinket M0 via USB. Power Jlink via USB.

"VTref" is used to detect target power is applied. It is a signal TO the programmer.

Update bootloader via JLink JTAG/SWD w/ uf2-samd21 - Trinket M0

Connect Jlink to Trinket M0 as above
Install openocd with brew install openocd
Modify uf2-samd21/scripts/dbgtool.js to use Jlink instead of EDBG.
- Change openocd path to use 0.1.0 or better: let openocdBin = "/usr/local/bin/openocd"
- Modify uf2-samd21/scripts/dbgtool.js: let zeroCfg = '/Users/tod/projects/samd/openocd-scripts/samd21-jlink.cfg'
  1. Must have new openocd-script samd21-jlink.cfg:
  2. Run "make burn" in uf2-samd21
  3. Alternatively, run:
```
cd uf2-samd21
node ./scripts/dbgtool.js fuses
node ./scripts/dbgtool.js ./build/trinket/bootloader.bin
```

Update bootloader via OpenOCD and JLink on commandline - Trinket M0

Install openocd as above
Get openocd_jlink_samd21.cfg
Get the bootloader-trinket_m0-v3.16.0.bin file from adafruit/uf2-samdx1
Connect Jlink to Trinket M0 as above
Program on commandline:
```
openocd -f ./openocd_jlink_samd21.cfg \
  -c "init; targets; halt; " \
  -c "at91samd bootloader 0;" \
  -c "program bootloader-trinket_m0-v3.16.0.bin verify;" \
  -c "at91samd bootloader 8192; reset; shutdown" 
```
NOTE: the at91samd bootloader 0; disables bootloader protection and allows you to rewrite the bootloader. The at91samd bootloader 8192; re-enables bootloader protection. (from this adfruit forum post)

Can also erase entire chip (assuming no bootloader lock):

openocd -f ./openocd_jlink_samd21.cfg -c "init; targets; at91samd chip-erase; shutdown"`

or in a more general way:

openocd -f ./openocd_jlink_samd21.cfg -c "init; targets; flash erase_sector 0 1 last; shutdown"`

Or list which targets are connected:

openocd -f openocd_jlink_samd21.cfg -c "init; targets; shutdown"

TODO: Get programming to work for Arduino sketches (specifically, can program but sketch doesn't run)

TODO: try:

-c "init; targets; reset halt; program sketch.bin 0x00002000

Update bootlaoder via OpenOCD and Atmel ICE on the commandline - Trinket M0

Install openocd and get bootloader-xxx.bin
Get openocd_atmel-ice_samd21.cfg
Connect Atmel ICE similar to JLink by using adapter like in image below
Program on commandline:
```
openocd -f ./openocd_jlink_samd21.cfg \
  -c "init; targets; halt; " \
  -c "at91samd bootloader 0;" \
  -c "program bootloader-trinket_m0-v3.16.0.bin verify;" \
  -c "at91samd bootloader 8192; reset; shutdown" 
```
NOTE: the at91samd bootloader 0; disables bootloader protection and allows you to rewrite the bootloader. The at91samd bootloader 8192; re-enables bootloader protection. (from this adfruit forum post)

You can also choose to install telnet and do these commands interactively:

In one terminal window run openocd:

% openocd -f ./openocd_atmel-ice_samd21.cfg 
Open On-Chip Debugger 0.12.0
Licensed under GNU GPL v2
For bug reports, read
http://openocd.org/doc/doxygen/bugs.html
Info : auto-selecting first available session transport "swd". To override use 'transport select <transport>'.
Info : Listening on port 6666 for tcl connections
Info : Listening on port 4444 for telnet connections
Info : CMSIS-DAP: SWD supported
Info : CMSIS-DAP: JTAG supported
Info : CMSIS-DAP: FW Version = 01.00.0021
Info : CMSIS-DAP: Serial# = J41800054170
Info : CMSIS-DAP: Interface Initialised (SWD)
Info : SWCLK/TCK = 1 SWDIO/TMS = 1 TDI = 1 TDO = 1 nTRST = 0 nRESET = 1
Info : CMSIS-DAP: Interface ready
Info : clock speed 400 kHz
Info : SWD DPIDR 0x0bc11477
Info : [at91samd21e18.cpu] Cortex-M0+ r0p1 processor detected
Info : [at91samd21e18.cpu] target has 4 breakpoints, 2 watchpoints
Info : starting gdb server for at91samd21e18.cpu on 3333
Info : Listening on port 3333 for gdb connections

And in another terminal window, run telnet and then openocd commands:


% telnet localhost 4444     
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Open On-Chip Debugger

targets TargetName Type Endian TapName State

0* at91samd21e18.cpu cortex_m little at91samd21e18.cpu running

reset halt
[at91samd21e18.cpu] halted due to debug-request, current mode: Thread xPSR: 0x21000000 pc: 0x00000264 msp: 0x20002de0

at91samd bootloader 0

flash erase_sector 0 1 last
SAMD MCU: SAMD21E18A (256KB Flash, 32KB RAM) erased sectors 1 through 1023 on flash bank 0 in 6.106292s

program bootloader-trinket_m0-v3.16.0.bin verify [at91samd21e18.cpu] halted due to debug-request, current mode: Thread xPSR: 0x21000000 pc: 0x00000264 msp: 0x20002de0 Programming Started Programming Finished Verify Started Verified OK

at91samd bootloader 8192

reset shutdown

Update bootlaoder via OpenOCD and STLink v2 - Trinket M0

Install openocd and get bootloader-xxx.bin
Get openocd_stlink_samd21.cfg
Connect Trinket M0 to STLink using only: GND, SWDIO, SWCLK, as in image below

Program on commandline:

openocd -f ./openocd_atmel-ice_samd21.cfg \
  -c "init; targets; halt; program bootloader-trinket_m0-v3.16.0.bin verify reset; shutdown"

Or interactively:


% telnet localhost 4444
Trying ::1...
telnet: connect to address ::1: Connection refused
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Open On-Chip Debugger

reset halt
[at91samd21g18a.cpu] halted due to debug-request, current mode: Thread xPSR: 0x61000000 pc: 0x00000264 msp: 0x20002de0 targets
TargetName Type Endian TapName State

0* at91samd21g18a.cpu hla_target little at91samd21g18a.cpu halted

flash erase_sector 0 1 last
SAMD MCU: SAMD21E18A (256KB Flash, 32KB RAM) erased sectors 1 through 1023 on flash bank 0 in 5.069648s

program /Users/tod/Downloads/bootloader-trinket_m0-v3.16.0.bin verify reset [at91samd21g18a.cpu] halted due to debug-request, current mode: Thread xPSR: 0x61000000 pc: 0x00000264 msp: 0x20002de0 Programming Started Programming Finished Verify Started Verified OK Resetting Target

todbot / samd21-programming-notes

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