PSOC 4 inline assembly ARM or Thumb?

Anonymous · ‎Nov 19, 2016

Hi folks,

I'm trying to embed some inline assembly in my project to work around areas where I can't get the compiler and optimizer to do what I want.

I pulled the lst file for the main loop, and I can see a couple of places that I want to tweak, to save a few precious clock cycles. What has me confused is that the lst formatting looks like ARM assembly, but AN89610 (Code Optimization document for PSOC 4) says that PSOC 4 uses Thumb 2.

Is there a way to choose ARM or Thumb?

I modified the main loop portion of the lst code, and swapped it in within asm(" .... "); The result is a "Cannot represent THUMB_OFFSET relocation in this object file" error during build. There's a referenced .s file and line number, but I can't find the actual file. I'm guessing it's just temporary during the build process....?

At this point, I'm getting almost the performance I need from my solution in C, but I have tried many variants, and only been able to find options that don't work. I do think I need the extra savings I can get from using assembly in the critical sections.

Thanks for the help,

Edit: I think I see the cause of the error: I missed that an array I'm using is represented as a label within the assembly block. I'll need to fix the assembly to correct address the array. I'm still rather confused about the ARM vs. Thumb stuff, though.

Paul

Anonymous · ‎Nov 19, 2016

This almost works:

        asm(
            "ldr r3, [%[datawrite]]\n"  //Get address of data write function
            "mov    r2, #125\n"
            "str r2, [r3]\n" //write data bus from r2
            :
            :   [addhigh] "l" (Pin_Address_High_PS),
                [addlow] "l" (Pin_Address_Low_PS),
                [datawrite] "l" (Pin_Data_DR),
                [dataread] "l" (Pin_Data_PS),
                [pinrw] "l" (CYREG_PRT0_PS),
                [buffer] "l" (buffer)
            );

It compiles, and builds, and programs, but it doesn't actually set the 125 value on the data bus. However, the resultant lst output does look pretty similar, so I think I'm close to getting this right.

On the other hand, one difference I observed between what's in the lst files and what will compile is f after the label of a forward jump. The generated assembly in the lst files had this, but it caused a compile failure when I used it in my code.

View solution in original post

PSOC 4 inline assembly ARM or Thumb?

PSOC 4 inline assembly ARM or Thumb?

Re: PSOC 4 inline assembly ARM or Thumb?