PIO0_8 on LPC812_MAX board doesn't pull-up

[fjrg76]

For a unknown reason, for me of course, the PIO0_8 in such a board is always read as logical LOW. The jumpers follow the factory settings. The pin is set as input:

#include "board.h"
#include <cr_section_macros.h>

...

    SystemCoreClockUpdate();
    Board_Init();

    Chip_GPIO_SetPinDIRInput(LPC_GPIO_PORT, 0, 8);

...

    bool tSup = Chip_GPIO_GetPinState (LPC_GPIO_PORT, 0, 8);

    // here always read false (or LOW), even when the pin is at 2.5V

Even though the pull-ups resistors are enabled by default, I set one 10K at the pin. This pin, the 14 in the 20 lead package, reads 2.5 volts, HIGH I guess, but internally at the chip it's read as LOW. I didn't found any conflict in this pin, looking both at the schematic and int the board.c library function, Board_Init(). But maybe I'm overlooking something.

Pins 0, 4 and 6 are set as inputs as well, and their readings are as expected: low when low, and high when high.

Any ideas? Thank you in advance!!

[vojtechhavlicek]

Hi,

PIO0_8 can works as XTAL so it is possible that somewhere in the init is enabled this functionality.

In this schematic https://www.embeddedartists.com/sites/default/files/support/xpr/LPC812_max/LPC812_MAX_Schematic_Rev3... is shown that PI0_8 is maybe connected to crystal.

Try to look if the chip runs from integrated crystal or external.

If internal than try this before GPIO init:

Chip_SWM_Init();

Chip_SWM_DisableFixedPin(SWM_FIXED_XTALIN);

Chip_SWM_Deinit();