5: BASIC Stamp Command Reference – POLLIN
BASIC Stamp Programming Manual 2.0c • www.parallaxinc.com • Page 215
POLLIN
BS1 BS2 BS2e BS2sx BS2p
POLLIN Pin, State
Function
Specify a polled-input pin and active state.
• Pin is a variable/constant/expression (0 – 15) that specifies the I/O
pin to use. This I/O pin will be set to input mode.
• State is a variable/constant/expression (0 – 1) that specifies
whether to poll the I/O pin for a low (0) or a high (1) level.
Quick Facts
BS2p
Available
actions in
response to
reaching the
desired State
1) Nothing,
2) Set polled-output pins to a specified state,
3) Run another program (in a specified program-slot),
4) Wait (pause program execution) until desired State is reached,
5) Any combination of 2, 3 and 4, above.
Special notes
• The polled-input pins are monitored (polled) in-between each command
within the PBASIC code.
• On the BS2p40, polled-input pins can be defined on both Main I/O and
Aux I/O pins. These are all active regardless of which group the
program happens to be using at the time of a polling event.
Explanation
The POLLIN command is one of a family of unique "polling" commands
on the BS2p module. The other commands in this family include
POLLMODE, POLLOUT, POLLRUN and POLLWAIT. The POLLIN
command is used to specify an input pin to monitor, or "poll", in-between
instructions during the rest of the PBASIC program. The BASIC Stamp
will then perform some activity (in-between instructions) when the
specified State is detected. The activity performed depends on the
POLLMODE, POLLOUT and POLLRUN commands.
The "polling" commands allow the BASIC Stamp to respond to certain I/O
pin events at a faster rate than what is normally possible through manual
PBASIC programming. The term "poll" comes from the fact that the
BASIC Stamp's interpreter periodically checks the state of the designated
polled-input pins. It "polls" these pins after the end of each PBASIC
command and before it reads the next PBASIC command from the user
program; giving the appearance that it is polling "in the background".
Table 5.53: POLLIN Quick Facts.
2
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