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AM6442: Prebuilt (and custom-built) sbl_null fail when booted via UART

Part Number: AM6442

Dear TI team,

I've been having issues booting my custom-built sbl_null on a custom board via UART. To rule out issues with my build I've tried using the pre-built SBL, and that fails in the same way.

I'm using Tera Term's built-in Transfer -> XMODEM functionality, but I've used tools/boot/uart_bootloader.py with the same result, i.e. ROM was executing again after uart_bootloader.py finished without errors:

grafik.png

The file is apparently transfered just fine, but the NULL bootloader doesn't seem to start up, and instead the ROM appears to executed immediately again, i.e. the output looks like:

[SOCID]CCC[SOCID]

The SOCID on this board is 02000000011a0000616d3634780000000000000048534653000002000000020002a6000000000000b018658ad99dc903c8c9bfb27b12751099920a042ad1dfea7b7ba57369f15546de285edde6a7b39a8bdc40a27b237f8fb1e57f245e80b929c1e28b024aa2ecc6ad0bc40b000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000aeabfba887873ecf9fc13aae04342216fa3923c933f150f17f19c1c8f19ee45e.

This issue is visible when using sbl_null.release.hs_fs.tiimage from MCU+ SDK 11.02.00.24 (md5sum dfde43b0731ebdd4cb06be2b000a6db3) or from MCU+ SDK 11.01, but not visible when booting e.g. sbl_null.debug.hs_fs.tiimage (264d151d2fb9e48974b3b929fe76ba90) from MCU+ SDK 11.02.

When putting the same sbl_null.release.hs_fs.tiimage on an SD card (as tiboot3.bin) it boots just fine.

I've been seeing the same issue with the sbl_null.release.hs_fs.tiimage from MCU+ SDK 11.01.00.17 but not with the prebuilt release NULL bootloader from SDK 11.00.00.15.

My custom bootloader fails when built as a debug build using CCS (both 12.8.1 and 20.4.0), but works when built as a release build. When building my custom bootloader via make (integrated into an MCU+ SDK tree), only the debug build works, not the release build (i.e. same as with the prebuilt SBLs).

  • Is there a known issue concerning SBLs and UART boot mode?
  • How can I debug this issue?

Best Regards,

Dominic