Code for Fast Switching of Bidirectional GPIO pins

[bruce]

Posted on August 05, 2008 at 20:18

Code for Fast Switching of Bidirectional GPIO pins

[bruce]

Posted on May 17, 2011 at 12:41

Is there a fast way to switch the GPIO's from input to output and vice-versa? In my application, I want all 16 pins on Port D to function as a bi-directional data bus.

Using the library, it appears that the only way is to use the GPIO_Init function. Can I just do for inputs: GPIOD->CRL = 0x44444444; GPIOD->CRH = 0x44444444; or for outputs: GPIOD->CRL = 0x22222222; GPIOD->CRH = 0x22222222; GPIOD->ODR = 0xABCD; // or whatever data value I want to write ??

[picguy]

Posted on May 17, 2011 at 12:41

I would use a bit of assembly code that does the following - -

ldr r0,=basePORTD ldr r1,=0x44444444 or 0x22222222 depending on your direction str r1,[r0,# GPIO_CRL] str r1,[r0,# GPIO_CRH] ; I might wait a few clocks before reading ; I assume no wait is needed before you str (data reg),[r0,GPIO_ODR] Unless you use your GPIOD structure for something else I would not bother updating it. -PICguy The following equates may prove useful basePORTD equ 0x40011400 GPIO_CRL equ 0x000 ;def low 8 bits of GPIO GPIO_CRH equ 0x004 ;def high 8 bits of GPIO GPIO_IDR equ 0x008 ;data register (input) GPIO_ODR equ 0x00C ;data register (output - all 16 bits) GPIO_BSRR equ 0x010 ;clr (top 16 bits), set (low 16 bits) GPIO_BRR equ 0x014 ;clr port bits set in low 16 GPIO_LCKR equ 0x018 ;lock given port config (complex setup sequence)