notes for SAMD21 programming in 2024

[todbot]

to do: add these to the readme.

Using Atmel ICE instead of Segger Jlink:

• On MacOS, install the following: brew install openocd telnet

• Wiring up device

  • Wire up "Vtref" to 3V3 not 5V
  • All other wiring as in README image

• Using Atmel ICE Save the below as openocd_atmel-ice_samd21.cfg:

  adapter driver cmsis-dap
  cmsis_dap_vid_pid 0x03eb 0x2141
  set CHIPNAME at91samd21e18
  source [find target/at91samdXX.cfg]

• Run openocd and connect to it with telnet

  • Running openocd should print out:

    % 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

  • Then telnet to it in another window:

    
    % 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

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

[todbot]

Image of the above setup:

[todbot]

And when using cheapie STLinkV2 clones:

• Wiring

  • Only three wires needed: SWDIO, SWCLK, GND
  • See photo below

• Create openocd_stlink_samd21.cfg with contents:

  source [find interface/stlink.cfg]
  set CHIPNAME at91samd21g18a
  set CPUTAPID 0x0bc11477
  source [find target/at91samdXX.cfg]

  (based on this blog post

• Run it with:

  openocde -f ./openocd_stlink_samd21.cfg

• Telnet to it like before Notice that messages are slightly different

  % 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 **