Toggle LED in custom application

Question

I'm trying to do something extremely simple but can't get it to work. Through the dev academy, I successfully loaded up and executed exercise 1. However, when I then try to "Create a New Application" (rather than "Add and existing appliction), running the exact same main.c code, I am not able to toggle the LEDs and none of the GPIOs seem to be configured. I'm guessing this has something to do with the generated files, but I don't know where to start looking. Please help! 
 BTW - I am able to attach with the debugger and see that the initialization seems to be completing without error and function call to the gpio toggle also returns with no error. main.c code for both applications is the following:

const struct device * dev0 ; 
 const int PIN = 29 ; 
 bool led_is_on = true ; 
 int ret ; 
 
 dev0 = DEVICE_DT_GET ( DT_NODELABEL (gpio0)); 
 
 if ( dev0 == NULL ) { 
 printk ( "device not found" ); 
 return ; 
 } 
 
 if (! device_is_ready ( dev0 )) { 
 printk ( "GPIO controller not ready" ); 
 return - ENODEV ; 
 } 
 gpio_pin_configure ( dev0 , PIN , GPIO_OUTPUT ); 
 while ( 1 ) { 
 gpio_pin_toggle ( dev0 , PIN ); 
 k_msleep ( SLEEP_TIME_MS ); 
 }

ovrebekk · Accepted Answer

Hi Jamie 
 Simon is currently unavailable, so I will help you out instead. 
 jmilliken said: 1) Why was this code inserted and from where is network_gpio_allow() called since it is clearly not called from main()? 
 The only reference to this function I can find is in the main.c file of the empty_app_core example. 
 The assumption is that if you are not running any code in the app core you want all the GPIO's available to the network core, since this is where you're running all your code. 
 In the end it is up to the app core to decide which pins are assigned to which core, which is why the app core has to run this during boot. 
 The SYS_INIT macro allows you to schedule code to be run during the boot process of the Zephyr kernel, before the main thread or any other application code has started. 
 The call to the various SYS_INIT functions will come from the init.c file in the zephyr\kernel folder, more specifically this line . 
 jmilliken said: Where are the initialization calls taking place since? 
 Essentially this is triggered by the z_cstart(void) function in the init.c file I mentioned earlier. 
 The various modules in your system that needs some kind of boot time initialization can define init functions using either the SYS_INIT macro, or one of the DEVICE macros for device drivers, as described here . 
 jmilliken said: 3) In STM32 applications, we also get an assembly file - e.g. startup_stm32h743zitx.s - which, upon reset, initializes all the memory then jumps to main. Where does this occur in Zephyr? 
 The reset code is implemented in /zephyr/arch/arm/core/aarch32/cortex_m/reset.S , which in turn calls the z_arm_prep_c() function in /zephyr/arch/arm/core/aarch32/prep_c.c , which among other things call the z_cstart() function in init.c that I mentioned earlier. 
 jmilliken said: 4) Does Zephy code adhere to CMSIS conventions? 
 Yes, all the hardware registers have CMSIS definitions available. 
 I believe you need to include <device.h> to get access to them. 
 Please note that all peripheral in the nRF devices use the NRF_ prefix, eg: 
 NRF_TIMER0->TASKS_START = 1; 
 Best regards Torbjørn

Toggle LED in custom application

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