Libraries
Background
lpcBitIO.c – bit device functions for LPC
These functions take a port (GPIO register) number and a bit mask – all those bits that have a 1 in the mask are affected.bitSetIO sets the configuration of a bit; bitIntIO controls its interrupt capabilities, and bitExistIO checks whether a pin exists in the hardware.
| Functions | |
|---|---|
| bitExistIO | test whether a bit or bits exist |
| bitIntIO | effect an interrupt configuration of a bit or bits |
| bitQueryIO | query the state of a bit or bits |
| bitSetIO | effect an action on a bit or bits |
bitExistIO – test whether a bit or bits exist
int bitExistIO(uint port, uint mask);
port – port in which the bit or bits reside
mask – mask of which bit(s) to test
returns 1 if all the bits in the mask exist in the specified port, or 0 otherwise; 0 is also returned if port is invalid
Note: this reports whether the bit exists in a microcontroller, not whether it is brought out to a board pin, or whether it supports interrupts.
bitIntIO – effect an interrupt configuration of a bit or bits
int bitIntIO(uint port, uint mask, uint action, vector handler);
port – port in which the bit or bits reside
mask – mask of which bit(s) to affect
action – one of BIT_RISE, _FALL, _RISEFALL, or _DISABLE
handler – interrupt handler to call, or NULL if _DISABLE
returns 0 if sucessful or negative if error (e.g., the bit does not exist or does not support interrupts, or handler already in use)
This first disables all interrupts for the specified bit(s). It then enables the pins as specified, unless handler is NULL.
The bit validity check only tests for whether all the specified bits are valid for interrupts, not whether they are brought out to a physical pin (they could still be used for self-wrought interrupts).
bitQueryIO – query the state of a bit or bits
int bitQueryIO(uint port, uint mask, uint *bits);
port – port in which the bit or bits reside
mask – mask of which bit(s) to query
bits – receives the state of the selected bits (other bits will be 0)
returns 0 if OK, −1 if error
The result will be −1 if port is not a valid port number. Bits are undefined if the selected bits do not exist. Bits may also be undefined or unpredictable if the pin corresponding to a bit is in alternative use (e.g., for ADC).
bitSetIO – effect an action on a bit or bits
int bitSetIO(uint port, uint mask, uint action);
port – port in which the bit or bits reside
mask – mask of which bit(s) to affect
action – one of BIT_ON, BIT_OFF, BIT_INVERT, or BIT_OPENDRAIN for output, or one of BIT_PULLUP, BIT_TRISTATE, or BIT_PULLDOWN for bit input
returns 0 if OK, −1 if error
BIT_ON, BIT_OFF, or BIT_INVERT set the specified bit(s) to output mode then sets the bit(s) as appropriate for the request (BIT_OFF sets each bit to 0, BIT_ON sets them to 1, BIT_INVERT flips each bit). BIT_OPENDRAIN sets the bit to open drain output mode and level high.
The actions BIT_PULLUP, BIT_TRISTATE, and BIT_PULLDOWN set the specified bit(s) to input mode with pull-up, neither pull-up nor pull-down, or pull-down.
After reset, bits are BIT_TRISTATE.
For example:
rc=bitSet(PORT1, BIT27, BIT_PULLUP);
The result is −1 if port is not a valid port number. Bits are undefined if the selected bits do not exist.