P0_26 on LPC54102

[skanda19]

Hello,

I been having some difficulties to control P0_26 on lpc54102. I know this pins is used to contro i2c1, but i our pcb design we map this pin to be used gpio (output), but I been having a hard time doing this, i feel kinda dumb hahah. 

I modified the blinky.c example code:

#include "board.h"

/*****************************************************************************

 * Private types/enumerations/variables

 ****************************************************************************/

#define TICKRATE_HZ (10) /* 10 ticks per second */

/*E1 - OUTPUT*/

#define     PORT0                           0

#define     RS485_REn_PORT                  PORT0

#define     RS485_REn_PIN                   26

#define     RS485_REn_OUT                   LPC_GPIO->DIR[RS485_REn_PORT]|=(1UL <<RS485_REn_PIN)

#define     RS485_REn_HI                    LPC_GPIO->B[RS485_REn_PORT][RS485_REn_PIN] = true

#define     RS485_REn_LO                    LPC_GPIO->B[RS485_REn_PORT][RS485_REn_PIN] = false

#define     RS485_REn_INP                   LPC_GPIO->DIR[RS485_REn_PORT]&=~(1UL <<RS485_REn_PIN)

#define     RS485_REn_IN                    LPC_GPIO->B[RS485_REn_PORT][RS485_REn_PIN]

#define     RS485_REn_TOG                   LPC_GPIO->NOT[RS485_REn_PORT]|=(1UL <<RS485_REn_PIN)

/*****************************************************************************

 * Public types/enumerations/variables

 ****************************************************************************/

/*****************************************************************************

 * Private functions

 ****************************************************************************/

/*****************************************************************************

 * Public functions

 ****************************************************************************/

/* Systick handler ISR */

void SysTick_Handler(void)

{

Board_LED_Toggle(0);

    RS485_REn_TOG;

}

/* main function (C entry point) */

int main(void)

{

int loop = 1; /* Used to fix the unreachable statement warning */

SystemCoreClockUpdate();

Board_Init();

Board_LED_Set(0, false);

    Chip_IOCON_PinMuxSet(LPC_IOCON, RS485_REn_PORT, RS485_REn_PIN,

                                    (IOCON_FUNC0 | IOCON_DIGITAL_EN | IOCON_GPIO_MODE));

    RS485_REn_OUT;

    RS485_REn_HI;

/* Enable SysTick Timer */

SysTick_Config(SystemCoreClock / TICKRATE_HZ);

while (loop) {

__WFI();

}

return 0;

}

but I am not been able to change the behavior of this pin, on our custom project and also the lpcXpresso 54102 board. when I change the configuration on debug mode the value goes back to 0 (keil). 

can someone help me sort this out ? 

thanks 

[skanda19]

both ports of the gpio are initialized. The pins are type I and I can control with the same method pins:

• 23
• 24
• 27
• 28

the only ones that i can't control is those 2:

• 25
• 26

IOCON are configured as follow:

but the state of the gpio no matter what remains low.

[skanda19]

the only way i can switch the line state, is when I change the invert bit. while this can be a work around, i would like to understand why is this happening ?

thanks,
RB

[Alex_Wang]

Hi, @skanda19 

I use the lpcxpresso54201 development board to control the LED blink of P0_26 (connect J2-16(P0_26)->J1-14(LED_GREEN)), for details, see the attached project configuration.

Hope this helps you.

Best regards, Alex

[skanda19]

hey alex! thanks for the support,

just to make sure:
you're initializing gpio (clk enable), setting iocon as gpio mode and setting pin 0_26 as alternate func 0,setting the pin as output and writting to B[port0][pin26].

am I correct ? or am I missing something ?

[Alex_Wang]

Hi, @skanda19 

Yes, I multiplexed P0_26 in gpio mode, initialized gpio (clk), and then wrote 0 or 1 to the pin to control the blink of the led.

Best regards, Alex

[skanda19 · Accepted solution]

Hey Alex, 

Thanks for the quick response. I was able to figure out what was the issue: 
In the user manual for the LPC54102, specifically in the IOCON  chapter mentions that the type I pin doesn't have any Pull-Up or Pull-Down resistors and if the user wants to use them as output the line will stay low because will be in and open-drain state. I solved the issue when I added an external resistor to be able to pull the level on the line. 

again, thanks for your help,
Ricardo B. 

[Alice_Yang]

Hello @skanda19 

You can refer to "led_blinky" demo to config gpio.

Check whether enabled gpio clock.

BR

Alice