RE: PROCESSOR-SDK-AM62X: How to write mixed C and assembly PRU code

Hello Sevki,

Yes, that guide will also apply to AM62x.

Have you gone through the mixed C and assembly examples in the PRU Getting Started Labs? You can find those here:
https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/10_00_07_04/exports/docs/common/PRU-ICSS/PRU-Getting-Started-Labs_Lab2.html

We will update those labs in the next couple months, so if you have any feedback I would love to hear it.

If you are still running into issues, please attach the code snippet that is causing errors, as well as your build commands and the error outputs.

Regards,

Nick

Hi Nick,

Thanks. My code is so long i am not copying everything here and waste your time. What i get in console is that:

**** Build of configuration Debug for project Test ****

"C:\\ti\\ccs1280\\ccs\\utils\\bin\\gmake" -k -j 20 all -O
 
Building file: "../main.c"
Invoking: PRU Compiler
"C:/ti/ccs1280/ccs/tools/compiler/ti-cgt-pru_2.3.3/bin/clpru" --include_path="C:/Users/sevkierdem/workspace_v12/Test" --include_path="C:/ti/pru-software-support-package-6.4.0/include/am62x" --include_path="C:/ti/ccs1280/ccs/tools/compiler/ti-cgt-pru_2.3.3/include" --include_path="C:/ti/pru_cgt/include" --include_path="C:/ti/ccs1280/ccs/tools/compiler/ti-cgt-pru_2.3.3/include" -g --diag_warning=225 --diag_wrap=off --display_error_number --endian=little -k --preproc_with_compile --preproc_dependency="main.d_raw"  "../main.c"
 
>> Compilation failure
subdir_rules.mk:9: recipe for target 'main.obj' failed
"../main.c", line 468: error #18: expected a ")"
"../main.c", line 478: warning #12-D: parsing restarts here after previous syntax error
1 error detected in the compilation of "../main.c".
gmake: *** [main.obj] Error 1
gmake: Target 'all' not remade because of errors.

**** Build Finished ****

and this is the inline assembly code that i have issues:

 __asm volatile(
               "MOV     r5, %[nHostCommand]                             \n"
               "MOV     r6, %[DATA]                                     \n"
               "MOV     r7, %[CLK]                                      \n"
               "MOV     r8, %[nTXData]                                  \n"
               "MOV     r12, %[direction_out]                           \n"
               "MOV     r13, %[direction_in]                            \n"
               "MOV     r15, %[__R30]                                   \n"
               "MOV     r16, %[__R31]                                   \n"

  nHostCommand and nTXData is binary like 0b0101010100101010 declared in C, they are C int variables and i want to use it in inline assembly and first assigned them to some registers, DATA and CLK is also C int variables and they equal to some  pins on board. direction_out and direction_in is also C int variables. I am using them as a parameter in C funtion named   void configure_gpio_direction(int direction) . So that was the first part of the code. In the middle there are some loops and conditional statements that i have no problem but at some point i call configure_gpio_direction function to make it writable or readable and that is the code for it:

"MOV     r4, r12                                         \n"  // r4 argument pointer
"BL     configure_gpio_direction                         \n"

i could not find anything about how to call C function from inline assembly. It can be false

Last part is where i get error:

                 :
                 : [direction_out] "r" (direction_out),
                   [direction_in]  "r" (direction_in),
                   [nHostCommand] "r" (nHostCommand),
                   [__R30]  "r" (__R30),
                   [DATA] "r" (DATA),
                   [CLK]  "r" (CLK),
                   [__R31] "r" (__R31),
                   [nTXData]  "r" (nTXData)
                 : "r4", "r5", "r6", "r7", "r8", "r12", "r13", "r15", "r16"
             );

error comes from first line and warning comes from last line. Thanks in advance.

Best Regards

Hi Nick,

thanks. I have another question: How can i reach the 32kB PRUSS shared memory located at 10000h from A53 core ? Thanks in advance.

Best regards

Hello Sevki,

Apologies for the delayed response here.

The A53 core would access it using the processor-wise memory map.

So from the Technical reference manual (TRM), Memory Map chapter, we see that the PRU memory (called ICSSM in the memory map) starts at 0x3004_0000

As you discussed, TRM section "PRUSS Global Memory Map" puts the shared ram at an offset of 0x1_0000.

So the A53 core would read or write to 0x305_0000 to access the SRAM.

You can find some examples of doing that math in the "Debugging" lab of the PRU Getting Started Labs:
https://software-dl.ti.com/processor-sdk-linux/esd/AM62X/10_01_10_04/exports/docs/common/PRU-ICSS/PRU-Getting-Started-Labs_Lab5.html

Regards,

Nick