keypad 4*4 with STM32* GPIOA

[adnen_speder]

Posted on April 05, 2012 at 13:03

salut, 

svp jr veux interfacer une clavier 4*4 avec un stm32 par les GPIO.... comment!!svp !!! NB : je met les 4 premier pins en 1     GPIO_SetBits(GPIOA,GPIO_Pin_0);           GPIO_SetBits(GPIOA,GPIO_Pin_1);          GPIO_SetBits(GPIOA,GPIO_Pin_2);          GPIO_SetBits(GPIOA,GPIO_Pin_3);

et j'esaye de faire le test sur les autres 4 pins !!!

#4x4-keypad

[emalund]

Posted on June 12, 2013 at 16:18

And thus the indirect reference to a specific document with a diagram, and specific comment that PA4..7 have 100K pull-ups.

Seems a bit high to me. Keypads are usually a bit distant from the chip, so, let's assume 100pF stray capacitance giving a risetime of 100p * 100k  ~ 10uS which, with fast code can be problematic.

[John F.]

Posted on June 13, 2013 at 09:40

Well switches often bounce and human fingers aren't all that fast either. I don't see a problem with the pull up value.

You might have pointed out that some switches need a minimum ''wetting'' current. Depends on the switch and the application. Outside the scope of this forum really.