I am investigating the lasts bug I had with my custom board. I stil have bad behavior of PB18 and PC19 after reset and before instantiating these IOs as output. But today I am facing an other problem. I have discovered long time ago that the CR2032 used to save RTC was not functionning properly on my custom board while it was working well with the G400HDR.
On my custom board, as soon as the CR2032 is inserted, its voltage drops down bellow the minimum voltage required to save the RTC. Therefore, there’s something wrong with my schematic. And current is drawn by the SOM. I discovered by using the G400HDR that when VBAT is applied, the PINs 179 (SHDN) and 177 (WKUP) are at 3V!
I go back to my documentation brochure; these pins are well described as SHDN and WKUP that’s why I have connected SHDN to GND and WKUP to VCC. Today in the G400D documentation these pins have been removed!!!
What’s happened there? What to do with these pins?