BASIC stamp manual v2.2

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5: BASIC Stamp Command Reference – BUTTON

BASIC Stamp Syntax and Reference Manual 2.2 • www.parallax.com • Page 137

BUTTON

BS1 BS2 BS2e BS2sx BS2p BS2pe BS2px

BUTTON Pin, DownState, Delay, Rate, Workspace, TargetState, Address

Function

Monitor and process a pushbutton input, perform auto-repeat, and branch

to address if button is in target state. Button circuits may be active-low or

active-high.

• Pin is a variable/constant/expression (0–15) that specifies the I/O

pin to use. This pin will be set to input mode.

• DownState is a variable/constant/expression (0 or 1) that specifies

which logical state occurs when the button is pressed.

• Delay is a variable/constant/expression (0 – 255) that specifies how

long the button must be pressed before auto-repeat starts. The delay

is measured in cycles of the BUTTON routine. Delay has two special

settings: 0 and 255. If Delay is 0, BUTTON performs no debounce or

auto-repeat. If Delay is 255, BUTTON performs debounce, but no

auto-repeat.

• Rate is a variable/constant/expression (0 – 255) that specifies the

number of cycles between auto-repeats. The rate is expressed in

cycles of the BUTTON routine.

• Workspace is a byte variable used by BUTTON for workspace. It

must be cleared to 0 before being used by BUTTON for the first time

and should not be adjusted outside of the BUTTON command.

NOTE: All RAM is cleared to 0 by default upon power-up or reset

of the BASIC Stamp module.

• TargetState is a variable/constant/expression (0 or 1) that specifies

which state the button should be in for a branch to occur. (0=not

pressed, 1=pressed)

• Address is a label that specifies where to branch if the button is in the

target state.

Explanation

When you press a button or flip a switch, the contacts make or break a

connection. A brief (1 to 20-ms) burst of noise occurs as the contacts scrape

and bounce against each other. By scanning an input within a loop to

NOTE: Expressions are not allowed as

arguments on the BS1. The range of

the Pin argument on the BS1 is 0 – 7.