IN ( expression )

When reading from IN (expression), -1 or 0 will be returned corresponding to the voltage level on the pin numbered expression. Why -1 and 0?  The main reason is that operations of operators like NOT are assumed to be bit-wise until there is a Boolean operation in the expression, and NOT 0 is equal to -1. 

This directive does not change the input/output configuration of the pin.

The ARMmite allows control of 24 pins (0..23), with pins 16..23 shared with the AD pins. On reset or power up the AD pins are configured as AD inputs.  To change those to digital IOs, the user must individually specify a control direction using INPUT(x), OUTPUT(x), DIR(x),  or IO(x) commands.  After that they will remain digital IOs until the next reset or power up.

For the ARMmite, PRO, ARMexpress and ARMexpress LITE these pin numbers correspond to the pin numbers shown in the Hardware Section. The numbering was assigned by physical location on the board. So DIR, HIGH, IN, INPUT, IO, LOW, OUT and OUTPUT use these physical pin assignments. But P0(pin) will use the bit assigned by NXP. Going forward new board designs will maintain the bit assignment from NXP for all keywords.

For the ARMweb, DINkit, SuperPRO, PROplus and PROstart these pin numbers correspond only to the Port 0 assigned by NXP, for instance DIR(3) corresponds to P0(3)

With version 8.11 of the firmware, ports beyond port 0, can be accessed as 32-63 for port 1, 64-95 for port 2, and so on. Or you may use the P1 .. P4 commands .


' Set pin 9 as an input

' Assume an external device has driven pin 9 high

PRINT "The current value of Input pin 9 is "; IN(9) AND 1

The current value of Input pins is 1

Differences from other BASICs

See also