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--- en:pfw:tasto [2025-06-22 00:26] – gelöscht - Externe Bearbeitung (Unbekanntes Datum) 127.0.0.1
+++ en:pfw:tasto [2025-08-04 11:28] (current) – [Forth implementation (noForth)] CC dazu mka
@@ Line 1: / Line 1: @@
+====== TASTO? ======
+A key (Italian tasto, Latin clavis) or a button is a control element that is operated by pressing and automatically returns to its original position when released.
+Forth has ''KEY?'' and ''KEY'' to query the computer's keyboard. I therefore call the query of a different individual key something else. Figure below shows such a key.
+{{:pfw:weissertaster.png?100|The small white button is on the breadboard at the bottom right of the picture.}}
+At [[en:pfw:clavis|CLAVIS?]] you can find out more about it.
+===== Implementation for MSP430G2553 =====
+Here, the button is connected to pin 7 of port 1 of the MSP430G2553 microprocessor MCU. See circuit diagram in code.
+==== I/O ====
+This circuit provides a digital input, with the pin itself being the voltage source.
+==== Pseudo code ====
+<code>
+Function:  PININ ( mask -- )
+           configure pin as input
+Function:  TASTO? ( mask -- f )  \ flag is true if the key is not pressed (high level at pin)
+           check digital voltage level
+</code>
+==== Forth implementation (noForth) ====
+The port pins are configured using registers.
+The configuration register table is specified in the code.
+The interrupt register indicates whether a falling edge was present.
+In the direction register, P1.7 is set to digital IN.
+The integrated **pull-up resistor is activated** to support the high level.
+No interrupt should occur, so it is disabled.
+The pin is used in the I/O function.
+Try more or fewer than five queries to eliminate the bouncing. (More on the [[pfw:topicofbouncing|topic of bouncing]].)
+<code>
+\ test button
+\ TI MSP430G2553 Launchpad with noForth mv 2553 240101
+\ CC by Michael Kalus, 20250804
+(*
+History
+20250609 P1.7 digital input
+addr acronym registername
+  P1IN    Input
+  P1OUT   Output
+  P1DIR   Direction
+  P1IFG   Interupt Flag
+  P1IES   Interrupt Edge Select
+  P1IE    Interrupt Enable
+  P1SEL   Port Select
+  P1SEL2  Port Select2
+  P1REN   Resistor Enable
+     Pin1.7--<---R---Button---GND
+	 R=47K
+*)
+hex
+constant pin7 \ mask for pin7 of port
+: PININ ( mask -- ) \  make pin to input
+  ( 020 )    \ P1IN    Input, read only
+dup 021 *bis \ P1OUT   Output, pullup resistor set
+dup 022 *bic \ P1DIR   Direction to IN
+dup 023 *bic \ P1IFG   Interupt Flag, cleared
+dup 024 *bic \ P1IES   Interrupt Edge Select, is irrelevant here.
+dup 025 *bic \ P1IE    Interrupt Enable, off
+dup 026 *bic \ P1SEL   Port Select,  I/O
+dup 041 *bic \ P1SEL2  Port Select2, I/O
+*bis \ P1REN   Resistor Enable, set
+  ;
+: TASTO? ( mask -- f )  \ Query button. debounced
+  >r
+  r@ 020 bit* 3 ms
+  r@ 020 bit* 3 ms
+  and
+  r@ 020 bit* 3 ms
+  and
+  r@ 020 bit* 3 ms
+  and
+  r@ 020 bit* 3 ms
+  and
+  r> =
+  ;
+\ test  mk
+: tt ( -- )
+  pin7 pinin
+  begin  ( 100 ms )  \ add more ms if you like
+  pin7 tasto? .
+  key? until
+  ;
+shield nn\
+freeze
+( finis)
+</code>
+==== Background information ====
+You can find them there: [[en:pfw:clavis|CLAVIS?]]
+===== Contributions =====
+===== Alternative Implementations =====
+You have another approach?
+Please add it at the end of this document.
+Sign in to post a comment.