ATSAMD21E18A - cannot write user_word_0 when BOOTPROT is on

[russfretenburg]

When BOOTPROT (bits 2:0 of user_word_0) is set to anything other than 7 (default, boot protect off), I cannot write to byte 0 of the user_word. If it is set to 7, I can successfully write a different value to it, for example 0xFA, which enables boot protection for 8192 Bytes. I can change byte 0 back to 0xFF using the Microchip Studio programmer interface, and then can write to it again with pymcuprog.

pymcuprog does not report any error and says the write is complete, but when I read the value back it has not changed. I also confirmed with Microchip Studio that the value did not change.

Testing on Windows 11 with Python 3.13.3.
pymcuprog version 3.19.4.61
programmer dongle: Atmel-ICE

Below are the steps to reproduce.

PS C:\Users\russf> pymcuprog -d atsamd21e18a read -m user_row -b 8
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700063793)
Debugger firmware version 1.42.161
Debugger hardware revision 0
Pinging device...
Ping response: 1001031C
Reading...
Memory type: user_row
---------------------------------------------------------
0x804000: FF C7 E0 D8 5D FC FF FF xx xx xx xx xx xx xx xx
---------------------------------------------------------


Done.
PS C:\Users\russf> pymcuprog write -U -d atsamd21e18a -m user_row -l 0xFA -v debug
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700063793)
Debugger firmware version 1.42.161
Debugger hardware revision 0
pymcuprog.programmer - INFO - Setting up programming session for 'atsamd21e18a'
pymcuprog.deviceinfo.deviceinfo - INFO - Looking for device atsamd21e18a
pymcuprog.nvm - INFO - SAM-M0+ stack is in Beta state
pymcuprog.samtarget - INFO - Target voltage read out: 2.53V
pymcuprog.samtarget - INFO - Connecting to SAMD2x DAP
pymcuprog.samtarget - INFO - Using SWD CLK of 2000000 Hz
pymcuprog.nvm - DEBUG - No specific initializer for this provider
Writing literal values...
pymcuprog.programmer - INFO - Write...
pymcuprog.programmer - INFO - Writing 1 bytes of data to user_row...
pymcuprog.samtarget - DEBUG - Is device locked?
pymcuprog.nvm - DEBUG - Writing 4 bytes to address 0x804000
pymcuprog.programmer - INFO - Write complete.
Done.
PS C:\Users\russf> pymcuprog -d atsamd21e18a read -m user_row -b 8
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700063793)
Debugger firmware version 1.42.161
Debugger hardware revision 0
Pinging device...
Ping response: 1001031C
Reading...
Memory type: user_row
---------------------------------------------------------
0x804000: FA C7 E0 D8 5D FC FF FF xx xx xx xx xx xx xx xx
---------------------------------------------------------


Done.
PS C:\Users\russf> pymcuprog write -U -d atsamd21e18a -m user_row -l 0xFF -v debug
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700063793)
Debugger firmware version 1.42.161
Debugger hardware revision 0
pymcuprog.programmer - INFO - Setting up programming session for 'atsamd21e18a'
pymcuprog.deviceinfo.deviceinfo - INFO - Looking for device atsamd21e18a
pymcuprog.nvm - INFO - SAM-M0+ stack is in Beta state
pymcuprog.samtarget - INFO - Target voltage read out: 2.56V
pymcuprog.samtarget - INFO - Connecting to SAMD2x DAP
pymcuprog.samtarget - INFO - Using SWD CLK of 2000000 Hz
pymcuprog.nvm - DEBUG - No specific initializer for this provider
Writing literal values...
pymcuprog.programmer - INFO - Write...
pymcuprog.programmer - INFO - Writing 1 bytes of data to user_row...
pymcuprog.samtarget - DEBUG - Is device locked?
pymcuprog.nvm - DEBUG - Writing 4 bytes to address 0x804000
pymcuprog.programmer - INFO - Write complete.
Done.
PS C:\Users\russf> pymcuprog -d atsamd21e18a read -m user_row -b 8
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700063793)
Debugger firmware version 1.42.161
Debugger hardware revision 0
Pinging device...
Ping response: 1001031C
Reading...
Memory type: user_row
---------------------------------------------------------
0x804000: FA C7 E0 D8 5D FC FF FF xx xx xx xx xx xx xx xx
---------------------------------------------------------


Done.
PS C:\Users\russf>

[russfretenburg]

After posting this issue I figured out that I can erase the user row first, and then write the complete user row again. So this will accomplish my goal, but I am not sure if this is the intended method or a limitation of the chip. It's possible that the Microchip Studio programmer does an erase and re-writes the whole user row in the background without the user seeing it.

[xedbg]

Interesting observation - I would expect that the "failure to fail" is probably that the Atmel-ICE is not picking up the error. In general I would recommend a --verify to post-verify (which should pick up the failure?)
We use this for manufacturing of CNANOs (which is really why we have SAMD21 support in the otherwise-8-bit utility), and thus don't exercise all corner cases.

[russfretenburg]

Thanks, I tried the write user row with --verify option and it does return an error, so at least that works.
I was using atprogram.exe on Windows and wanted a Linux substitute - that's how I found this utility. Anyway it's working for me now as long as I erase the user row first, then reprogram it.

[Knochi]

same problem here, how did you erase the user row?
i used pymcuprog erase -d atsamd21e18a -m user_row
so my device had 0x5D D8 E0 C7 FF
after erase it was 0x5D D8 E0 C7 FA

shouldn't the default value be "0x7 - 0bytes" for bootprot or do i mix something up?
and i cannot write 0xFF to the first byte after the erase neither.

pymcuprog write -d atsamd21e18a -m user_row -o 0 -l 0xFF --verify
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700037806)
Debugger firmware version 1.41.137
Debugger hardware revision 0
Pinging device...
Ping response: 1001030A
Writing literal values...
Verifying literal values...
pymcuprog.programmer - ERROR - Verify failed for user_row memory:
pymcuprog.programmer - ERROR - Verify mismatch starting at location 0x000000: 0xFF vs 0xFA (is the memory section erased?)    
Done.

[russfretenburg]

same problem here, how did you erase the user row? i used pymcuprog erase -d atsamd21e18a -m user_row so my device had 0x5D D8 E0 C7 FF after erase it was 0x5D D8 E0 C7 FA

shouldn't the default value be "0x7 - 0bytes" for bootprot or do i mix something up? and i cannot write 0xFF to the first byte after the erase neither.

pymcuprog write -d atsamd21e18a -m user_row -o 0 -l 0xFF --verify
Connecting to anything possible
Connected to Atmel-ICE CMSIS-DAP from ATMEL (serial number J42700037806)
Debugger firmware version 1.41.137
Debugger hardware revision 0
Pinging device...
Ping response: 1001030A
Writing literal values...
Verifying literal values...
pymcuprog.programmer - ERROR - Verify failed for user_row memory:
pymcuprog.programmer - ERROR - Verify mismatch starting at location 0x000000: 0xFF vs 0xFA (is the memory section erased?)    
Done.

Hi Knochi, it's working for me using the below commands:

Commands for pymcuprog usage with ATSAMR21e18a:

Read user row:
pymcuprog read -d atsamd21e18a -m user_row -b 8

Erase full user row (user_word_0 and user_word_1):
pymcuprog erase -d atsamd21e18a -m user_row

write user row with BOOTPROT OFF:
pymcuprog write -d atsamd21e18a -m user_row -l 0xFF 0xC7 0xE0 0xD8 0x5D 0xFC 0xFF 0xFF

Program bootloader with erase first and verify:
pymcuprog -d atsamd21e18a write --verify --erase -f

Program application with verify:
pymcuprog -d atsamd21e18a write --verify -f

write user row with BOOTPROT ON for 8192 Bytes:
pymcuprog write -d atsamd21e18a -m user_row -l 0xFA 0xC7 0xE0 0xD8 0x5D 0xFC 0xFF 0xFF