MSP-EXP430G2 Launchpad Setting Gpio

I. Background knowledge: Use of logical operators

When the program initializes, it is recommended to use direct assignment for registers with uncertainties in the reset state (such as Pxout), and it is best to modify the registers using logical operators in other cases.

Direct Assignment

REGISTER =0xF0;

"Turn on" a bit (1), keep the other bits unchanged

// turn bit x on // both on

"Close" a bit (0), keep the other bits unchanged

// turn bit x off // both off

"Flip" a bit (reverse), keep the other bits unchanged

// Toggle bit x // Toggle Both

Two. Register for Gpio

As shown in the following table.

Register	short Form	Register Type	Initial State     &nb Sp
Input	pxin	Read only	-
Output	pxout	read/write	unchanged
Direction	pxdir	read/write	Reset with puc
pullup/pulldown   resistor Enable	Pxren	Read/write	Reset with PUC

pxdir: Setting the direction of the IO Pin

-Bit = 0: input (default)

-Bit = 1: Output

pxren: Enable pin internal pull-up/pull-down, typical pull-up/pull-down resistor resistance 35KOHM

-bit=0: Disable the upper/lower pull resistor function (default)

-Bit=1: Enable up/down resistor function

pxin: reflects the level on the PIN

-Bit=0: input is low level

-Bit=1: input is high level

pxout:

-When the up/down resistor is disabled, the function is to set the output level high and low

--bit=0: Output High Level

--bit=1: Output Low Level

-When the Enable up/down resistor, the function is to select the pull up or pull down

--bit=0: Drop down

--Bit=1: Pull-up

Three. Initialization program example

Example 1: Setting P1.0 to Output

1#include"io430.h"2 3 voidMainvoid)4 {5   //Stop watchdog timer to prevent time out reset6Wdtctl = Wdtpw +Wdthold;7 8P1out =0;//Initialize the output state before changing the pin to an output9P1dir |= BIT0;//P1.0 Output 0Ten  One      while(1) A     { -         //code ... -     } the  -}

Example 2: Setting P1.3 as a pull-up input

1#include"io430.h"2 3 #definePUSH2 BIT34 5 voidMainvoid )6 {7     //Stop watchdog timer to prevent time out reset8Wdtctl = Wdtpw +Wdthold;9 TenP1out =0; OneP1out |= PUSH2;//Initialize the Pullup state AP1ren |= PUSH2;//Enable internal Pullup -P1dir &= ~push2;//set P1.3 to input mode (default) -     //State on P1.3: (p1in & PUSH2) = = PUSH2 the  -      while(1) -     { -         //code ... +     } -    +}

Resources

Msp430x2xx Family User ' s Guide
msp430g2553 Datasheet

MSP-EXP430G2 Launchpad Setting Gpio