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--- projects:3dprinting:flashforge_creator_3_pro_fan_fix:patching [2024/10/24 21:50] – admin
+++ projects:3dprinting:flashforge_creator_3_pro_fan_fix:patching [2024/10/24 22:03] (current) – admin
@@ Line 16: / Line 16: @@
         clz        r0, r0                 @             (0x1318da b0 fa 80 f0)
         b          #0x1318ec              @             (0x1318de 05 e0)
-                                          @ ... continue at lsrs r0, r0, #0x5 and then b #0x1316d6
+@  - or -
+@       b.w        #0x1318ec              @             (0x1318de 00 F0 05 B8)
+@                                         @ ... continue at lsrs r0, r0, #0x5 and then b #0x1316d6
 @
 @  LAB_001318e0 (prepare for M26 command)
@@ Line 28: / Line 32: @@
 </code>
-But during testing, the printer crashed at receiving command M26 with an "illegal instruction" error. A backtrace in gdb showed where the problem was: The branch instruction at address 0x1318de, b #0x1318e8, occupied not 2 but 4 bytes and thus overwriting partly the function for M26.
+But during testing, the printer crashed at receiving command M26 with an "illegal instruction" error. A backtrace in gdb showed quickly where the problem was: The branch instruction at address 0x1318de should have been a "b #0x1318e8" (05 e0), but the assembler converted the branch instruction into "b.w #0x1318ec" (00 F0 05 B8) and thus overwriting partly the function for M26.
 Why [[https://sourceware.org/binutils/docs/as.html|GNU as]] encoded the branch instruction into a 32 bit instruction I do not yet know. The easiest solution was to accept that the instruction may occupy 32 bit, and branch from one instruction earlier. So instead of "0x1318da  clz r0,r0" followed by "0x1318de  b #0x1318ec" it would just do "0x1318da  b #0x1318e8":

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