STM32F411RET6, current consumption varies depending on code size

[florin]

Posted on December 23, 2015 at 13:07

Hello,

I started to develop a device with STM32F411RET6, working on battery.I saw, that the current consumption, varies with 0.8mA depending of code size or code alignment in MCU flash.Does anyone know something about this?I made a simple test:MCU, 8MHz, HSI divided by 2, prefetch and cache  enabled.I work in MikroPascal, Mikroelektronika.code, first test, current 3.5mAbegin  while true do     // 3.5 mA    begin//      nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;    end;end.ASM:;Spera.mpas, 102 ::                 begin0x05DC        0xF7FFFE4C  BL        6320x05E0        0xF7FFFE22  BL        5520x05E4        0xF000F812  BL        15480x05E8        0xF7FFFE34  BL        596;Spera.mpas, 103 ::                 while true doL__main2:;Spera.mpas, 106 ::                 nop;nop;0x05EC        0xBF00    NOP0x05EE        0xBF00    NOP;Spera.mpas, 107 ::                 nop;nop;0x05F0        0xBF00    NOP0x05F2        0xBF00    NOP;Spera.mpas, 108 ::                 nop;nop;0x05F4        0xBF00    NOP0x05F6        0xBF00    NOP;Spera.mpas, 109 ::                 nop;nop;0x05F8        0xBF00    NOP0x05FA        0xBF00    NOP;Spera.mpas, 110 ::                 nop;nop;0x05FC        0xBF00    NOP0x05FE        0xBF00    NOP;Spera.mpas, 111 ::                 nop;nop;0x0600        0xBF00    NOP0x0602        0xBF00    NOP;Spera.mpas, 112 ::                 nop;nop;0x0604        0xBF00    NOP0x0606        0xBF00    NOP;Spera.mpas, 113 ::                 end;0x0608        0xE7F0    B        L__main2;Spera.mpas, 114 ::                 end.L_end_main:L__main_end_loop:0x060A        0xE7FE    B        L__main_end_loop; end of _maincode, second test, 4.2mAbegin  while true do     // 4.2 mA    begin      nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;      nop;nop;    end;end.ASM:_main:;Spera.mpas, 102 ::                 begin0x05DC        0xF7FFFE4C  BL        6320x05E0        0xF7FFFE22  BL        5520x05E4        0xF000F814  BL        15520x05E8        0xF7FFFE34  BL        596;Spera.mpas, 103 ::                 while true do     // 4.2 mAL__main2:;Spera.mpas, 105 ::                 nop;0x05EC        0xBF00    NOP;Spera.mpas, 106 ::                 nop;nop;0x05EE        0xBF00    NOP0x05F0        0xBF00    NOP;Spera.mpas, 107 ::                 nop;nop;0x05F2        0xBF00    NOP0x05F4        0xBF00    NOP;Spera.mpas, 108 ::                 nop;nop;0x05F6        0xBF00    NOP0x05F8        0xBF00    NOP;Spera.mpas, 109 ::                 nop;nop;0x05FA        0xBF00    NOP0x05FC        0xBF00    NOP;Spera.mpas, 110 ::                 nop;nop;0x05FE        0xBF00    NOP0x0600        0xBF00    NOP;Spera.mpas, 111 ::                 nop;nop;0x0602        0xBF00    NOP0x0604        0xBF00    NOP;Spera.mpas, 112 ::                 nop;nop;0x0606        0xBF00    NOP0x0608        0xBF00    NOP;Spera.mpas, 113 ::                 end;0x060A        0xE7EF    B        L__main2;Spera.mpas, 114 ::                 end.L_end_main:L__main_end_loop:0x060C        0xE7FE    B        L__main_end_loopThanks in advance.Best regards,Florin.

[Tesla DeLorean]

Posted on December 23, 2015 at 13:45

The flash lines are quite wide, do you see the same variability if you run from SRAM?

Do you configure the flash, wait states, and prefetch before running this code?

[florin]

Posted on December 23, 2015 at 21:30

Thanks for reply.

I investigate more and seems to be a problem with BRANCH (B) instruction.If instruction are in sector0, depending of the instruction address (position on flash), the current consumption will grow...I moved all the code, to start from sector1 and problem disappear...Maybe ST team can investigate more.Thanks. 

[Tesla DeLorean]

Posted on December 24, 2015 at 01:43

Maybe ST team can investigate more.

For that kind of thing to happen you'll have to provide significantly more complete test cases rather expect them to recreate your exact conditions. Understand this is a User Forum, ST does not heavily participate here, so you might do better discussing your issue directly with an FAE.