We are running a survey to help us improve the experience for all of our members. If you see the survey appear, please take the time to tell us about your experience if you can.
I've written a boot loader for the Atmel SAM4E device which is working to a point, it can receive new application code via SPI, erase flash and write to flash, but I don't understand how to execute the new application. I've learned the VTOR can be relocated, but I'm not sure how. (my application sits at address 0x00420000).I'm very new to writing code for ARM, so I'd appreciate any help.
Many thanks
Paul
Hello again Paul,
it is the Intel Hex, isn't it?I understand and it would be reasonable.However, it is strange "((start_fn *) *((uint32_t *) 0x00420004))()" causes a stack overflow.Did you set the stack pointer before execution the asm statement?Otherwise, you should add the "__attribute__((naked))" attribute to the bootloader function in order not to use stack.
Best regards,Yasuhiko Koumoto.
I have found the problem
It would seem that on boot a number of things are 'assumed' as being in a certain state by the compiler.
If I disable the global interrupts, cpu_irq_disable() , before jumping, and then re-enable them, cpu_irq_enable() in the application, it works.
My next challenge is reading and writing a single value to a specific location in flash (say 0x0048FFFF) so I can detect if I should be self writing or jumping to the application.
Hello Paul,
I am afraid to change a single position of a flash would be impossible as the flash should be block erased before writing a new code.
If you want to do so, you can copy the whole data of the flash block to SRAM, changing a value on the SRAM and write back to the SRAM contents to the flash.
Best regards,
Yasuhiko Koumoto.