GPIO Instrumentation

Pin toggling is often a simple and useful mechanism for debugging applications. We will now add some simple instrumentation to profile the read and write cycles of the Mass Storage device.

Todo: Find the implementation of the ui_start_read () function in the file ui.c. This can be easily done by opening ui.h, selecting the function, and using the Goto Implementation option on the context menu.

Add instrumentation as shown here, which toggles GPIO0 for read accesses and GPIO1 for write accesses:

voidui_start_read(void){// GPIO0 high
    port_pin_set_output_level (EXT1_PIN_GPIO_0, true);}voidui_stop_read(void){// GPIO0 low
    port_pin_set_output_level (EXT1_PIN_GPIO_0, false);}voidui_start_write(void){// GPIO1 high
    port_pin_set_output_level (EXT1_PIN_GPIO_1, true);}voidui_stop_write(void){// GPIO1 low
    port_pin_set_output_level (EXT1_PIN_GPIO_1, false);}

Find the board_init.c file and add initialization of GPIO0 and 1. This can be added by copying the LED_0_PIN initialization in system_board_init (void)

// GPIO0 to outputport_pin_set_config(EXT1_PIN_GPIO_0,&pin_conf);// GPIO1 to outputport_pin_set_config(EXT1_PIN_GPIO_1,&pin_conf);

You can also comment out the LED toggle, as it is not relevant here.

voidui_process(uint16_t framenumber){/*if (0 == framenumber) {
		LED_On(LED_0_PIN);
	}
	if (1000 == framenumber) {
		LED_Off(LED_0_PIN);
	}*/}

Todo:

Build the project/solution (F7)
Program the application into the target device using Start Without Debugging (Ctrl + Alt + F5)
Switch to Data Visualizer to see the results
Select both the Power interface and GPIO and start visualizing

Todo:

Open the control panel
Uncheck channel B
Uncheck GPIO 2 and 3

The power graph should now look similar to the previous exercise. Now perform a disk format through Windows, and note how the GPIO 0 and 1 signals toggle. Stop the visualizer or disable auto-scrolling and zoom in to an interesting bit. One can clearly see how each read and write access has a GPIO toggle to indicate a Start and Stop condition.

Since this is a fully compliant disk drive, try a few other operations and see how the read and write access events are affected:

Create a new text file
Add content using notepad
Save the file
Re-open the file
Delete the file

Tip: Read caching by the operating system might cause read access not to be executed until the cache is flushed after a write.