The jump logic in main_f1.c of PX4 bootloader is hard to comprehend

KevenDing1 · March 20, 2019, 2:02am

Hi！
There are two Macro definition （INTERFACE_USART and INTERFACE_USB） in line 313. But they already defined in hw_config.h(I am useing v3),the “timeout” will be setted 5000 in here. so it seem that we couldn’t jump to app immediately by line 340. I couldn’t understand it,where is the answer in the code？ PX4-Bootloader/main_f1.c at master · PX4/PX4-Bootloader · GitHub

JulianOes · March 20, 2019, 8:26am

Can you elaborate what you’re trying to do and what your problem is? Maybe that will make it easier for me to answer.

KevenDing1 · March 21, 2019, 2:58am

I want to use the bootloader in my stm32 for IAP，but i found that when the app not left a cookie the bootloader still could’t jump to app immediately because of the two Macro definition.

JulianOes · March 21, 2019, 11:01am

I’m still lost. What is IAP. What cookie? What about the macro definition?

KevenDing1 · March 22, 2019, 1:19am

hi Julian
I‘m sorry for that not described it clearly. IAP is “In Application Programming”,the cooike is a flag which was setted by app for update. you can find it in line 322 https://github.com/PX4/Bootloader/blob/master/main_f1.c , i’m puzzled because i can’t understand how the bootloader jump to app when not expected to wait in the bootloader .

JulianOes · March 25, 2019, 9:33am

If no timeout is set then it jumps directly here, right?

github.com

PX4/Bootloader/blob/master/main_f1.c#L342


	}


#endif


	/* look for the magic wait-in-bootloader value in backup register zero */




	/* if we aren't expected to wait in the bootloader, try to boot immediately */
	if (timeout == 0) {
		/* try to boot immediately */
		jump_to_app();


		/* if we returned, there is no app; go to the bootloader and stay there */
		timeout = 0;
	}


	/* configure the clock for bootloader activity */
	clock_init();


	/* start the interface */
	cinit(BOARD_INTERFACE_CONFIG, USART);