I’m trying to adapt FreeRTOS-Kernel/portable/GCC/ARM_CM0/port.c for Raspberry Pi Pico . The Pico has a hardware divider whose state must be saved for context switches. The state consists of 4 32-bit words. (See hw_divider_save_state and hw_divider_restore_state in pico-sdk/divider.S at master · raspb…

You managed to get hardware? This statement doesn’t look right: [image] carlk3: SIO_BASE: .word SIO_BASE Is SIO_BASE the address of the hardware divider peripheral? If so you should be able to eliminate this line altogether. Gcc should manage putting the value into the literal pool for yo…

[image] jefftenney: You managed to get hardware? I managed to get one. Then, I quickly learned that the easiest way to get debugging capability is to use a second one as a “PicoProbe”. Been waiting for that one for months. [Why was I such a cheapass? Should’ve gotten the 3-pack.] [image] …

In FreeRTOS style, you probably need to #define SIO_BASE in port.c. Alternatively, change the #SIO_BASE to #0xD0000000 – the value of SIO_BASE.

[image] jefftenney: Alternatively, change the #SIO_BASE to #0xD0000000 – the value of SIO_BASE. /* hw_divider_save_state */ " ldr r2, =#0xD0000000 \n"/* SIO_BASE */ I tried that, but it still hangs. Then I tried commenting out this line: //" bcc MY1 \n" but it still hangs. I…

" UDF #0" should cause an undefined instruction exception.

I looked at the port.c you attached above, and it doesn’t look like you modified vPortStartFirstTask, which you will need to do. It seems your first task is never even starting.

Ah, that was a problem! I changed " adds r0, #32 \n"/* Discard everything up to r0. */ to " adds r0, #48 \n"/* Discard everything up to r0. */ and now I am getting a hard fault for free! Unfortunately, Link Register (LR): A5A5A5A5 Program Counter (PC): A5A5A5A4 is not very …

Glad it worked! Not to get too far into the weeds on this thread, but I’m curious about this solution. Why save the divider state? Does the compiler use the divider directly? Or is there a target usage model where protecting the divider with critical section or mutex would not be suitable? I as…

By default, the Pico SDK overrides the / (and similar) operators to use the hardware divider. The work-around is to add pico_set_divider_implementation(TARGET compiler) in the CMakeLists.txt. If you fail to do this you get no error indications, just weird and subtle intermittent data errors, and…

Extending the xPortPendSVHandler save area for ARM_CM0

Kernel

carlk3 (Carl Kugler III) March 20, 2021, 12:10am 9

Thanks so much, Jeff!

The version that runs: port.c (24.9 KB)

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Extending the xPortPendSVHandler save area for ARM_CM0

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