By far the simplest and most commonly used debug method is the humble print statement. The Linux kernel offers this in the form of printk.
Getting to the U-Boot command line is fundamental, a whole host of things must be correct to get there. Clocks, memory, serial…: these are some of the things that need to be working before you talk to your board at all.
In electronics product development, touchscreens can be difficult to stress test; and whilst there are several sophisticated systems available for touchscreen stress testing, there are other ways to get the job done – like a low-tech approach… For example, take a look at this rig built from a child’s toy. Our engineer built it as part of the debug process to try to fix a failed touchscreen unit. Thanks to our brightly-coloured debugger, we discovered that the touchscreen controller chip itself was unreliable. The rig kept tapping the screen over and over and over again. However, what the debug process uncovered was that it took slightly more than a mere tap-tap-tap motion to uncover the bug. So: Tap-tap-tap motion = unit functioning normally. Tap-slide-and-up motion (closer to an actual [...]